Transcriber’s Note
  Italic text displayed as: _italic_
  Bold text displayed as: =bold=




  FIELD ARTILLERY
  MATERIEL

  NOTES ON THE DEVELOPMENT,
  USE AND CARE OF MODERN FIELD ARTILLERY
  EQUIPMENT, INCLUDING THE

  3” Field Gun, American, French and
  British 75s, the 4.7” Gun, 155-mm
  Howitzer, GPF, Fire Control Instruments,
  Signal Equipment and small
  arms used by the Field Artillery—automatic
  pistol, automatic rifle and
  the Browning machine gun.

  _Compiled by_

  JAMES P. KELLY
  1ST LIEUT. FIELD ARTILLERY
  U. S. ARMY


  COPYRIGHT
  BY
  THE UNIVERSITY CO-OPERATIVE STORE
  UNIVERSITY OF MISSOURI
  COLUMBIA, MO.

  1920




DEDICATION


To those efficient officers and inspiring gentlemen who interested the
“youngsters” of the Yale batteries in the service of their country,
and, in a time of peace, prepared them for the duties which they later
performed in a time of war, this book is gratefully and respectfully
dedicated.


ARTILLERY OF THE FUTURE.

[Illustration: SELF-PROPELLING CATERPILLAR MARK VII 75-MM. GUN. MODEL
1916.]

[Illustration: SELF-PROPELLING CATERPILLAR MARK II 155-MM. FILLOUX
GUN.]




INTRODUCTION.


The compiler of this volume believes that the Field Artillery
student should possess a broad, general knowledge of the history
and development of ordnance, with some idea of the elements of gun
construction; that he should be acquainted with the organization,
ideals and practicalities of modern field artillery armament; that he
should know the ammunition and the guns in our Field Artillery service
with their care and maintenance.

It is also believed that in the R. O. T. C. units of Field Artillery
the student should make the complete 3” equipment the basis of his
knowledge of materiel. He should become thoroughly and familiarly
acquainted with this weapon, and, to a lesser extent, with the other
light pieces which are in present use. The reason for this being that
our experience in the World War has shown that a thorough knowledge
of one class of materiel permits a ready adaptation to any other
type. He should also know the manner of functioning of the 4.7” and
155-mm rifles, with a somewhat more intensive knowledge of the 155-mm
howitzer—and with a sound knowledge of the capabilities and limitations
of all.

To complete his instruction in materiel he should know the use and care
of Fire Control equipment, Signal equipment, and the small arms used in
the field artillery, pistol, automatic rifle and machine gun.

The lack of a single volume covering the above has been the cause
of the compilation of this book. The compiler hopes the R. O. T. C.
student will find in it a text which will be interesting, instructive
and comprehensive. To the lieutenants in charge of Department “A” and
to those who aspire to that responsibility it is hoped that this work
will prove a valued addition to their professional libraries.

The subjects covered herein have been taken wholly or in part from the
various official handbooks, from “Ordnance and Gunnery, U. S. M. A.,”
“Naval Gunnery, U. S. N. A.,” “America’s Munitions,” “Gun Making in
the U. S. A.,” “Ordnance and Gunnery for Field Artillery Officers,”
“Artillery Firing,” “The Field Artillery Journal,” Ordnance Doc. 2033,
from lecture notes taken at the School of Fire, Brigade Training
Pamphlets, and various other sources.

The compiler is indebted to Lt. Col. Lloyd E. Jones, F. A. and Major H.
C. Jackson, F. A. for the valuable advice and the helpful assistance
they rendered in this compilation.




CONTENTS.


                                                                    Page

  Chapters I. Definitions.                                            11

  II.  History and Development of Materiel.                           16

  Biblical references—Use by Romans in Punic
  wars—Greeks; Chinese use of pyrotechmy;
  French field artillery in the time of Charles
  VIII; Gustavus Adolphus and artillery in
  the 17th century; Louis XIV; Gribeauval’s
  work in 1765; Shrapnel, 1808; Smooth
  bores to rifles, middle of 19th century;
  French “75;” Period 1897 to date.

  III.  Elements of Gun Design and Construction.                      27

  Guns—wire wrapped and built-up; twist;
  breechblocks; carriages; traversing
  mechanisms; elevating mechanisms;
  recoil systems. Air and spring recuperators;
  shields; sights; wheels; trails.

  IV. Modern Armament.                                                46

  Discussions of types of artillery and their
  organization; missions and guns suitable
  to accomplish different missions;
  ideal and practical types for divisional
  corps and army artillery.

  V.  Three-inch Field Gun.

  Weights and dimensions.                                             62

  Description of gun, carriage, caisson and
  limbers; functioning of principal parts.

  Mounting and dismounting.

  VI. 75-mm Model 1897 (“French 75”).                                 84

  Weights and dimensions.

  Description and functioning of principal
  parts.

  Care, preservation, dismounting.

  VII.  75-mm Model 1916 (“American 75”).                            105

  Weights and dimensions.

  Description and functioning of principal
  parts.

  Care, preservation, dismounting, mounting.

  VIII.  75-mm Model 1917 (“British 75”).                            147

  Weights and dimensions.

  Description and functioning of principal
  parts.

  IX.  4.7” Rifle Model 1906.                                        154

  Weights and dimensions.

  Description and functioning of principal
  parts.

  X.  155-mm Rifle (Filloux Gun) (GPF).                              160

  Weights and dimensions.

  Description and functioning of principal
  parts.

  XI.  155-mm Howitzer Model 1918.                                   167

  Weights and dimensions.

  Description and functioning of principal
  parts.

  Notes on dismounting and mounting—cleaning.

  XII.  Explosives, Ammunition and Fuzes.                            199

  Explosives—classes, fillers, H. E., nitrogen
  compounds.

  Ammunition—classes, discussion of fixed,
  semi-fixed and separate ammunition,
  primers, charges, construction of different
  types of shell, care.

  Fuzes—principle of operation, arming, classification,
  precautions, tables of fuzes
  giving description, use, etc.

  Ammunition marking.

  XIII.  Care and Preservation of Materiel.                          236

  Oils and cleaning materials; tools and accessories;
  care and cleaning of different
  parts of carriages, emptying, cleaning
  and filling cylinders, cleaning bore,
  breech, springs, etc.; general instructions
  for care of cloth, leather and
  metal equipment. Cleaning schedules.

  XIV.  Fire Control Equipment.                                      258

  Sights—line, front and rear, panoramic;
  model 1915 and 1917 with their use,
  care and verification. Range Quadrant,
  care, use and adjustment. B. C.
  Telescope, model 1915 and Aiming
  Circle model 1916, with their use,
  care and adjustment. Range Finder,
  1 meter base, use, care and adjustment.
  Field Glasses. Fuse Setters.

  XV.  Signal Equipment.                                             285

  Telephones and Monocord Switchboards—description,
  use, adjustments, trouble
  shooting and care.

  Projectors—description, use, adjustment,
  service code for lamps and buzzer, conventional
  signals.

  Pyrotechnical signaling, classification of
  rockets, use, code.

  Panels—liaison with airplanes, signals, description
  of panels, panel code.

  Flags—classification, use of semaphore and
  wig-wag.

  Radio—Description of equipment, SCR-54
  and SCR-54-A Sets, methods of operation,
  use of vacuum detectors, precautions,
  sources of trouble, maintenance,
  reception of airplane signals.

  XVI.  Small Arms.                                                  315

  Pistol, machine gun and automatic rifle—description,
  use and care.

  XVII.  Motors                                                      328

  Reconnaissance car, Dodge, Harley-Davidson
  motorcycles. 5-ton tractors,
  ammunition trucks, cargo trucks. How
  to drive, sources of trouble, maintenance.

  Appendices.                                                        349

  A.  Gunner’s Examinations—preparations,
  Cannoneers’ “Don’ts,” training gun
  crews.

  B.  Tabular comparison of light guns used                          370
  in World War.

  C.  Table of Equivalents.                                          371

  Index.




LIST OF ILLUSTRATIONS


  _Title_        _Page_

  Artillery of the Future      Frontispiece
  Diagram Hydro-Springs and Hydro-Pneumatic Recoil Systems      41
  3-inch Field Gun Breech Mechanism      Facing  63
  Carriage Model 1902, Plan View      Facing  65
  Elevating Gear      67
  Traversing Gear      Facing 66
  Recoil Controlling Mechanism      Facing  69
  Caisson Limber, Model 1916      73
  Caisson, Model 1902      Facing  74
  75-mm Field Gun, Model 1897 (French)      85
  Breech Mechanism      86
  Firing Mechanism      88
  Gun Carriage, Longitudinal Section      90
  Gun Carriage, Rear View      91
  Gun Carriage, Left Side      92
  Gun Carriage, Right Side      93
  Gun Carriage, Plan View      94
  Wheel Brake Mechanism (Abatage)      96
  Range Elevating Mechanism      98
  75-mm Field Gun, Model 1916 (American)      107
  Breech Mechanism      108
  Breech Mechanism      109
  Gun Carriage, Left Side      112
  Gun Carriage, Right Side      113
  Gun Carriage, Rear View      116
  Gun Carriage, Plan View      117
  Gun Carriage, Longitudinal and Transversal Sections      119
  Recoil Mechanism      122
  Valve Turning Gear      125
  Angle of Site Mechanism      128
  Elevating Mechanism      130
  Traversing Mechanism      132
  75-mm Field Gun, Model 1917 (British)      148
  Breech Mechanism      149
  Recoil Mechanism      151
  Gun Carriage, Plan View      152
  4.7-inch Gun, Model 1906, Longitudinal Section      155
  Gun Carriage, Left, Plan and Rear Views      158
  155-mm Gun, Model 1918, (GPF) (Filloux)      161
  Longitudinal Section in Battery      163
  Carriage and Limber, Traveling Position      Facing 165
  155-mm Howitzer, Model 1918      169
  Carriage and Limber      Facing  166
  Carriage Unlimbered      Facing  167
  Breech Mechanism      171
  Breech Mechanism      172
  Firing Mechanism      174
  Longitudinal Section      180
  Carriage, Left Side      183
  Elevating Mechanism      184
  Traversing Rollers      186
  Traversing Mechanism      188
  Air and Liquid Pumps      190
  Howitzer Carriage, Plan View      191
  Quadrant Sights, Model 1918      193
  DeBange Obturator      205
  Mark II-A Primer      207
  155 Steel Shell Mark IV      210
  155 Shrapnel Mark I      212
  4.7-inch Gun Ammunition      213
  3-inch Gun Ammunition      Facing  214
  Detonating Fuze, Mark III      225
  Detonating Fuze, Mark V      226
  45 Second Combination Fuze, Mark 1      230
  21 Second Combination Fuze, Model 1907 M      231
  75-mm Gun Ammunition      234
  Rear Sight, 3-inch Field Gun      259
  Panoramic Sight, Model of 1917      261
  Panoramic Sight, Model of 1915      264
  Range Quadrant, 3-inch Field Gun      266
  Battery Commander’s Telescope, Model 1915      271
  Aiming Circle      275
  Diagram of Range Finder Principle      279
  Range Finder, Rear View      Facing  280
  Range Finder Tripod      Facing  281
  Three-Steps in Range Finding      Facing  282
  Fuze Setters      Facing  284
  Camp Telephone      Facing  286
  Diagram Telephone Circuit      287
  Diagram Radio Circuit      307
  The Automatic Pistol, Cal. 45, Model 1911      Facing  316
  Receiver, Barrel and Slide      Facing  317
  Component Parts      Facing  318
  Component Parts Assembled      Facing  319
  Ammunition Truck      Facing  334




CHAPTER I

DEFINITIONS.


In the study of any subject which is rather technical in nature, it is
absolutely essential that the reader be familiar with the meaning of
the words and phrases which must be used in the matter to be discussed.
If the subject matter is to be understood there must be a common
phraseology. The reader is therefore strongly urged to perfect his
knowledge of the following short vocabulary before passing on to the
matter which follows.

 =Ammunition.= A general term applied to all forms of powders, shells,
 cartridges, primers, etc.

  (a) _Fixed Ammunition._ When the powder charge is enclosed in a
  metallic container which is fixed to the projectile, it is called
  “=Fixed Ammunition=.”

  (b) _Semi-Fixed Ammunition._ When the charge and metallic container
  are a fixed unit but are not fastened to the projectile, it is called
  “=Semi-Fixed Ammunition=.”

  (c) _Separate Ammunition._ When the powder charge is contained in
  bags separate from the projectile and containing not a fixed but a
  varying charge, it is called “=Separate Ammunition=.”

 =Artillery.= All firearms not carried by hand, excepting machine guns.
 It is divided into two general classifications: (1) artillery of
 position, and (2) mobile artillery.

  (1) Artillery of Position is that which is permanently mounted in
  fortifications.

  (2) Mobile Artillery consists of two classes: first, artillery
  designed to accompany an army in the field; second, railway artillery
  which requires tracks for its transportation.

 =Ballistics.= The science of hurling projectiles or of the motion of
 projectiles in their flight.

 =Bore.= The hole which extends from the muzzle to the breech. The
 passageway for the projectile. That part of the tube which is bored
 out.

 =Breech.= The rear end of the gun, tube, or barrel.

 =Caisson.= A two-wheeled vehicle which supports an ammunition chest.
 The wheeled equipment of a gun section consists of one gun with its
 limber and one caisson with its limber. For a caisson section it
 consists of two caissons with their limbers.

 =Caliber= (=Calibre=). The diameter between the highest points in the
 bore.

 =Carriage, gun.= Usually understood to mean all the piece except the
 tube with its appurtenances and the limber.

 =Cartridge case.= A hollow cylinder shaped to fit the bore. A
 container for the propelling charge.

 =Charge.=

  (a) _Propelling._ A quantity of powder used in the bore to generate
  the gases which propel the projectile from the gun.

  (b) _Bursting._ A quantity of powder used in shrapnel to strip off
  the head of the projectile and to force out the balls.

  (c) _Explosive._ The matter used in a shell to detonate it at the end
  of its flight.

 =Cradle.= In general, that part of the carriage which houses the
 recoil and counter-recoil mechanisms.

 =Elevating Mechanism.= The device used to elevate the gun through a
 vertical arc in order to give the gun an elevation corresponding to
 the desired range at which the piece is to be fired.

 =Fire Control Equipment.= Those instruments used to compute firing
 data, observe and correct the fire, such as B. C. Telescopes, Aiming
 Circles, Range Finders, etc.

 =Firing Mechanism.= A device located in the breechblock for exploding
 the primer and thus causing the ignition of the powder charge.

 =Fuze.= That part of the round which is fastened to the point or to
 the base of the projectile and causes the latter to be detonated or
 exploded near the time or the place desired.

 =Fuze Setter.= A device used to set time fuzes in such a manner that
 shrapnel or shell will burst at or near the desired height in air.

 =Gun.= A metallic tube from which projectiles are hurled by gases
 generated from the ignited powder. In general, all fire arms; but
 in Field Artillery terms, comparatively long-barreled weapons using
 relatively high muzzle velocity in contra-distinction to the howitzers
 and mortars.

 =Howitzer.= A weapon which differs from a gun in that for the same
 caliber it uses a shorter tube, lower muzzle velocity and generally
 a more curved trajectory. From two to seven varying strengths of
 propelling charges may be used in the howitzer. This gives it
 selective angles of fall, and allows the howitzer to reach targets
 that are hidden from the flat trajectories of guns.

 =Initial Velocity.= The speed with which the projectile first moves.

 =Limber.= A two-wheeled carriage which is sometimes used to carry an
 ammunition chest and always used to support the weight of the trail
 of the piece or caisson. It adds the other two wheels to make a
 four-wheeled vehicle.

 =Materiel.= A term used in the Field Artillery in contra-distinction
 to Personnel.

 =Mortar.= A weapon using for the same caliber, a barrel much shorter
 than the corresponding howitzer. Used at short ranges with extreme
 steep angles of fall to reach highly defiladed targets.

 =Muzzle.= The front end of the bore.

 =Muzzle Velocity.= Speed or velocity of the projectile measured as it
 leaves the muzzle.

 =Ogive.= The rounded shoulder of the projectile.

 =Ordnance.= Arms, ammunition, and their accessories.

 =Piece.= A fire arm, small or large.

 =Primer.= Device used to insure ignition of the propelling charge.

 =Projectile.= The effect-producing part of the round. The bullet-like
 form which is thrown toward the target.

 =Quadrant, gunners.= A device for measuring angles of elevation.

 =Recoil Mechanism.= That part of the piece which checks the recoil—or
 kick—that always occurs when a piece is fired. It generally includes
 the counter-recoil mechanism which restores the tube “into battery”
 after it has fired.

 =Rifle.= A gun. A weapon with a comparatively long barrel and high
 muzzle velocity. Rifles under 6 inches seldom use over two different
 charges. Term used in contrast to Howitzer or Mortar.

 =Rifling.= The lands and grooves in the bore of the piece which
 imparts to the projectile during its passage through the bore, the
 rotary motion that increases accuracy and range.

 =Round.= Consists of the primer, cartridge case or powder bags,
 projectile and fuze. For light Field Artillery the round weighs about
 18 lbs and the projectile about 15.

 =Shell.= A projectile which secures its effect by the force of its
 detonation, the bursting of its walls, and the fragmentation and
 velocity of the fragments. Also used as a gas carrier.

 =Shrapnel.= A projectile which secures its effect by the expulsion in
 the air of lead balls with shot-gun like effect.

 =Trail.= That part of the piece which extends from the axle to the
 rear and transmits the force of recoil to the ground through the trail
 spade. Usually supports the elevating and traversing mechanisms.

 =Traversing Mechanism.= A device used to give the piece direction by
 moving it through a horizontal arc.




CHAPTER II

HISTORY AND DEVELOPMENT OF MATERIEL.


In taking up the study of materiel, the Field Artillery student should
know something of the history and development of ordnance and the
reasons for the various changes which have taken place from time to
time.

The sole use of a gun is to throw a projectile. The earliest projectile
was a stone thrown by the hand and arm of man—either in an attack
upon an enemy or upon a beast that was being hunted for food. Both of
these uses of thrown projectiles persist to this day, and, during all
time, from prehistoric days until the present, every man who has had a
missile to throw has steadily sought for a longer range and a heavier
projectile.

In ancient times the man who could throw the heaviest stone the
longest distance was the most powerfully armed. During the Biblical
battle between David and Goliath, the arm of David was strengthened
and lengthened by a leather sling of a very simple construction.
Much practice had given the youthful shepherd muscular strength and
direction, and his stronger arm and straighter aim gave him power to
overcome his more heavily armed adversary.

Projectile-throwing machines were developed after the fashion of a
crossbow mounted upon a small wooden carriage which usually was a
hollowed trough open on top and upon which a stone was laid. The thong
of the crossbow was drawn by a powerful screw operated by man power,
and the crossbow arrangement when released would throw a stone weighing
many pounds quite a distance over the walls of a besieged city or from
such wall into the camps or ranks of the besiegers. This again was an
attempt by mechanical means to develop and strengthen and lengthen the
stroke of the arm and the weight of the projectile. The Bible states
that King Usia (809-757 B. C.) placed types of artillery on the walls
of Jerusalem. The Romans used it in the Punic Wars. The Alexandrian
technicians established scientific rules for the construction of early
weapons. Athenaeus reports catapults having a range of 656 meters and
that the gigantic siege tower at Rhodes successfully resisted stone
projectiles weighing 176 pounds.

References to explosives are to be found in works as old as Moses.
Archimedes is said by Plutarch to have “cast huge stones from his
machines with a great noise;” Caligua is said by Dion Cassius to have
had machines which “imitated thunder and lightning and emitted stones;”
and Marcus Graecus in the eighth century gives a receipt of one pound
of sulphur, two of willow charcoal and six of saltpetre, for the
discharge of what we should call a rocket.

The use of Greek fire was understood as early as the sixth century,
but powder was earliest used in China, perhaps a thousand years before
Christ, and was introduced to European notice by the Saracens.

From the discovery of gunpowder by the English monk Bacon in 1248,
sixty-five years elapsed before a Franciscan monk produced the
first gun in Germany, about 1313. The first guns were of a small
breech-loading type, supported in front by crossed sticks and anchored
by a spike at the breech. Later these guns were fastened to cradles,
the latter being mounted on sleighs, and finally, in 1376, the
Venetians produced the first wheel mounts, which had become common by
1453, when the Turks took Constantinople.

The ancient carriages were remarkable because of the fact that in
general design they embodied the same principals which are included in
the field carriages of to-day. One example from the fifteenth century
shows a breech-loading gun mounted in a cradle supported by trunnions
on the forward extension of the trail over the axle. The cradle was
elevated by a pin-and-arc arrangement, supported on the trail. The axle
supported by wheels passes through the trail to the rear of and below
the cradle trunnion support and in front of the point of attachment of
the elevating arc.

Field guns fell into disuse about 1525 with the introduction of
musketry, and remained so until 1631, when Gustavus Adolphus gave
artillery its true position on the battlefield.

Swedish artillery reigned supreme in the early part of the seventeenth
century. Gustavus introduced marked changes by making the guns and the
carriages lighter and handier, and by adapting their movements to those
of the other arms and to the requirements of the battlefield. In this,
as in all his military efforts, his motto was mobility and rapidity of
fire.

In 1624 Gustavus had all his old types of guns recast into newer models
and the following year he himself contrived a gun which three men and
one horse could maneuvre to good effect. It was an iron three and four
pounder with a cartridge weighing less than a pound and consisting
of a charge held in a thin wooden case wired to a ball. This was the
first artillery cartridge, the original fixed ammunition. The gun
was afterwards used in other European armies and known as the “piece
Suedoise.” Not only had it the advantage of lesser weight but its
cartridge was always ready to fire and it could be fired eight times to
the six times of the infantry musket of that day.

In the wars against the Poles, Gustavus employed with profit the
so-called leather cannon, a fact which shows how lacking the times were
in artillery power. These guns were invented in the early 1620s by a
Colonel Wurmbrandt, and consisted of a thin copper tube reinforced
by iron bands and rings, then bound with rope set in cement, the
whole covered with sole leather. The tube was made to screw in and
out because it grew heated by from eight to twelve charges and had to
be cooled. The gun carriage was made of two planks of oak. The gun
without the carriage weighed about ninety pounds and was fired with a
light charge. They were used during 1628-29 and then gave way for four
pounder cast-iron guns which remained in common usage in Europe until
artillery was reorganized by Frederick.

Gustavus’ batteries excited universal admiration. Grape and canister
were generally employed in the field guns and round shot only in
the siege guns. Artillery was used massed or in groups and also
with regiments of foot soldiers. Gustavus was probably the first to
demonstrate the real capabilities of artillery.

Mortars throwing bombs were first used at the siege of Lamotte in 1634.
Hand grenades, shells, fire-balls, etc., came into more general use as
the German chemists made their new discoveries. Artillery practice grew
to be something of a science; experts took it up and the troops were
better instructed. Regimental artillery, that is, artillery with the
infantry, was attended by grenadiers detailed for the work. There were
special companies for serving the reserve guns.

The period following the Thirty Years’ War—the middle of the
seventeenth century—gave no great improvement to the art of war
but there were many marked advances in the matter of details of
construction. During the era of Gustavus it was Sweden that led in
making war more modern; during the era of Louis XIV it was France.

Artillery ceased to be a guild of cannoneers as it long had been and
became an inherent part of the army. More intelligence was devoted to
it and more money spent on this arm of the service; it grew in strength
and importance, and was markedly improved. But while the artillery
service ceased to be a mere trade, it did not put on the dignity of a
separate arm, nor was the artillery of any great utility in the field
until well along in the eighteenth century. Guns, however, in imitation
of the Swedes, were lightened, particularly so in France; powder was
gradually compounded on better recipes; gun-metal was improved; paper
and linen cartridges were introduced; gun carriages were provided
with an aiming wedge; and many new styles of guns and mortars, and
ammunition for them were invented.

Science lent its aid to practical men, and not only exhausted chemical
ingenuity in preparing powder and metal, but mathematical formulas
were made for the artilleryman, and value of ricochet firing was
discovered. Louis XIV founded several artillery schools, and initiated
the construction of many arsenals. Fontainebleau, the French artillery
school which trained many Americans during the World War had its
beginning in this period. Finally, the artillery was organized on a
battery and a regimental basis, and careful rules were made for the
tactics of the guns. These were served by dismounted men and generally
hauled by contract horses.

Although sensibly improved, the artillery was far from being skillfully
managed and was slow firing; it usually stood in small bodies all
along the line of battle. It was heavy and hard to handle and haul,
principally because the same guns were used for both siege and field
work, and was far from being, even relatively to the other arms, the
weapon which it is to-day.

In 1765 General Gribeauval of France introduced artillery improvements,
especially in the carriages, and formed a distinct artillery service
for the field which was lighter than the old service and was drawn by
teams which were harnessed double as they are to-day.

Howitzers were introduced in France in 1749. The weapons were given an
early sort of perfection by the Dutch. The term “howitzer” comes from
the German “haubitz.” In 1808 the first shrapnel appeared at Vimera. It
was invented by an English colonel by the name of Shrapnel. At the time
it was known as case shot. The type employed by Napoleon, had a fuze
that could be used at two different ranges. The French still have this
type in their armament.

Field artillery now began to appear in the form which it was to retain
with but a few changes, until the era of the modern field carriage. The
cradle disappeared, muzzle-loading guns cast with trunnions taking its
place, and a stepped wedge resting on the trail superseded the pin and
arc. With the exception of the gun, most parts of these carriages were
of wood and were to remain so until 1870, when metal carriages came
into general use. Muzzle loading guns had supplanted breech-loaders
because of the poor obturation and the many accidents resulting from
use of the latter type. Although numerous experiments were made,
breech-loading guns did not come into vogue again until 1850, when the
experiments of Major Cavalli (1845), the Walnendorff gun (1846) and the
Armstrong gun (1854), produced satisfactory types.

Up to 1860 practically all guns were smooth bore. Even during the
Civil War the smooth bore was generally used, although the rifled gun
began to make an appearance and was used in small numbers by both
sides at the battle of Gettysburg. Some breech loaders began to appear
at the same time. Improvement in the ballistic properties of the gun
necessitated a corresponding improvement in the sighting facilities. In
1880 rifled breech loading and built-up steel cannon came into general
use. Rifled guns shoot accurately and as a result, improved methods in
direct laying were devised.

The period between from 1880 to the present, has brought about changes
in gun construction which, possibly, have been equaled in importance
to artillery only by the present change which is taking place in the
means of artillery transportation and self-propelling mounts. In this
period in rapid succession came the modern breechblock and with it
the rapid firing gun. This brought about the change to the present
system of breaking the force of recoil of the gun and restoring it to
its firing position without disturbing the position of the carriage.
This added to the possibilities of rapid and more accurate fire. Then
came the invention and use in the field artillery of smokeless powder.
Previous to this time the great amount of smoke produced by the black
powder when the piece was fired retarded the rapidity of fire because
it enveloped the materiel in a thick cloud of smoke which obscured the
target and made it impossible to fire again until the smoke had blown
away. It made concealed positions for the artillery almost impossible.
The advent of smokeless powder made firing more rapid and made possible
the selection of concealed positions. This in turn made indirect fire
feasible and necessitated the development of better sights. Indirect
fire increased the rapidity of fire and gave to the commanders of
firing units a greater control over their fire. With the use of recoil
mechanisms and shields for the guns, the cannoneers were permitted to
serve the piece continuously—a condition which was impossible with the
recoiling carriage. The shields made it almost impossible to put the
gun out of action unless some vital part of the mechanism was destroyed.

The first of the modern carriages which were produced in the early
nineties should be classified as semi-rapid carriages, as the recoil
brakes were so abrupt that the carriage was not stable and jumped
considerably, gaining for the type the sobriquet of “grass-hopper
guns.”

In 1897 the immortal French “75” was born, the pioneer of all modern
quick-firing field guns, which still maintains its superiority in many
respects over later designs.

In 1902 our own 3-inch field gun was produced and still finds favor
among many of our field artillery officers, even over the French “75.”

The Deport carriage brought to this country from Italy, in 1912,
introduced to us the split trail, high angle of fire, wide traversing
type of field gun carriage. This carriage was extensively tested by
the Ordnance Department; by the Field Artillery Board at Fort Riley,
Kansas; and by the School of Fire for Field Artillery, at Fort Sill,
Oklahoma. The Field Artillery Board unqualifiedly approved of the
Deport carriage and recommended that it be adopted. The School of Fire
for Field Artillery also approved of this type.

In 1916 the United States produced a 75-mm field gun which featured a
split trail with an elevation of 57 degrees which permits its use as
an anti-aircraft weapon and a variable length of recoil which prevents
the breech from hitting the ground at the extreme elevations. It has a
traverse of 800 mils in comparison to the 106 of the French 75 and the
142 and 140 of the British 75 and American three-inch field gun.

The outbreak of the late war saw all modern armies largely equipped
with guns resembling the French “75” in a long-run recoil mechanism,
weight of projectile and weight of carriage, etc. The fact that the
largest number of horses which could best be handled to maneuver the
light guns—about 6—could not pull over a long period a gun or caisson
with its limber if the weight was more than about 4500 pounds, resulted
in the practical standardization of light guns in all armies. So in
1914 we see that time and development had given light gun perfection
and mastery of artillery technique to the French while the Germans,
probably, possessed the most efficient artillery program. The German
types of weapons were more varied and perhaps better suited to the
varying artillery needs in rendering that assistance to the infantry
for which the artillery exists.

In our service during the World War, French 75s and the 155-mm Howitzer
were used as divisional artillery. Two regiments of the light guns and
one regiment of 155-Howitzers were assigned to each infantry division.
As the war progressed guns and howitzers ranging from the 4.7” rifle,
up to, and including 14 and even 16-inch naval guns on railroad mounts,
were used as Corps and Army artillery.

Thus artillery development has gone steadily forward. Every military
power has striven with the aid of its best engineers, designers
and manufacturers to get a stronger gun, either with or without a
heavier projectile, but in every case striving for greater power. As
a special development and a not too important one, due to its lack
of effectiveness in comparison to its cost, we find the now famous
long range gun of the Germans, successfully delivered a projectile
approximately 9 inches in diameter into Paris punctually every twenty
minutes from a point about 75 miles distant. The Germans used three of
these guns in shelling Paris. Their life was probably limited to about
75 rounds due to the excessive demands made upon the materiel.

The American Field Artillery Service now has before it four types
of field gun carriages, namely our 3” model of 1902; the French 75
M-1897; the British 18 pounder, M-1905 converted to a 75-mm (known as
the model of 1917); and our 75-mm model, 1916. There is being produced
(1919-20) an improved model of 1916 75-mm carriage on which the St.
Chamond pneumatic recuperator, adopted jointly by the American and
French governments, will be substituted for the spring recuperators;
and the French 75-mm gun will be substituted for our shorter calibered
type. From these types one must be selected. An intelligent selection
involves a consideration of what may be expected in the future in
order that it may best fit in with the new types yet to be evolved.

For horsed artillery—and horse artillery will be with us for some years
to come—the limiting features of draft and man power will still pertain.

For tractor-drawn mobile artillery, the limiting feature is the
tractive power of the tractor with relation to the weight of the gun
and carriage, the unit being physically limited in weight by the
supporting-power of the pontoon bridge which is about 10,000 pounds per
vehicle.

For Caterpillar Artillery.—By that is meant guns mounted on caterpillar
tractors—the limiting features are power and weight, coupled with the
weight limitations of the pontoon bridge. To circumvent the question of
weight, the load may be divided by mounting the motor by an electric
generator on one caterpillar and the gun with an electric motor, on the
other, a transmission cable connecting the two vehicles.

In conclusion it might be said that one of the greatest changes which
has ever taken place in the development of field artillery is now
underway in the form of motorization. Prior to 1917 horse traction had
been the sole means of transporting mobile field artillery. The limit
of the capabilities of horse traction placed a weight limit upon gun
construction and to some extent upon artillery tactics. The increase in
the ratio of field artillery to infantry, the corresponding demand for
artillery types of horses and the decrease in the availability of the
latter as the war continued, combined with the great improvements which
were constantly being wrought in mechanical transportation as the war
lengthened, opened the way for artillery motorization.

The French began by placing their 75s on trucks for rapid changes of
position. All the armies saw the possible advantages to be gained from
the use of trucks with artillery but none planned—nor have any since
put into practice—the extensive use of trucks, caterpillar tractors and
motor transportation for personnel, which the United States planned on
her entrance into the war. It was planned to equip about one-third of
the A. E. F. artillery regiments with complete motor equipment. This
plan did not entirely materialize but after the armistice the 3rd Field
Artillery Brigade of the 3rd Division was completely motorized and its
practice marches in Germany were most successful and full of promise
for the future. To date the motorization of all our mobile Field
Artillery, with the exception of about fifty per cent of the light
field guns, has been authorized.

Motor traction gives a better performance than animal. While the
latter, especially with the light field guns, possesses great mobility,
it is not a sustained nor a persistent mobility; it is more easily
exhausted and requires longer to recuperate. These are points of vital
importance from a military viewpoint.

In 1920 a self-propelling caterpillar mounted with a 75-mm gun, model
1916, was tested with a view to ascertaining the ability of the motor
to function in water, i. e. fording streams, etc. The caterpillar
successfully moved through ice water which completely submerged the
carburetor.

Passenger cars for the transportation of personnel, four wheel drive
trucks with caterpillar tractors for the transportation of the
materiel, and the development of self-propelling mounts for the 75 and
155 rifles are the latest and the most important developments in field
artillery materiel.




CHAPTER III

ELEMENTS OF GUN CONSTRUCTION AND DESIGN


“A gun is a machine by which the force of expanding gas is utilized for
the purpose of propelling a projectile in a definite direction.” It is
essentially a metal tube closed at one end, of sufficient strength to
resist the pressure of the gases caused by the combustion of the powder
charge in the confined space at the closed end of the tube behind
the projectile. The rapid combustion of the powder, which produces a
high temperature, gives rise to a pressure uniformly exerted in all
directions within the confined space. The energy exerted is used in
forcing the projectile from the tube.


TUBES

Due to the effort of the large amount of superheated gas generated,
which tends to expand in all directions, tremendous rending stresses
are set up in the tube. Formerly these stresses were met by a sheer
mass of metal, but, as the size of the projectiles increased and the
necessary pressure to give them muzzle velocity increased, the size
of the guns increased beyond the practical limits of mobility. This
was at first offset by forgings of refined alloyed steels, but even
these failed to keep pace with the increasing pressure desired. The
new condition was met by the introduction of the “built-up” and the
“wire-wrapped” guns. The modern built-up gun is made by assembling one
or more superimposed cylinders around a central tube. The superimposed
cylinders, whose inside dimensions are slightly smaller than the
outside dimensions of those on which they are to be assembled, are
expanded by heat sufficiently to allow them to be assembled over the
tube. The subsequent contraction on cooling causes each of them to
exert a uniform pressure on the cylinder immediately underneath. This
method of assembling is called “shrinkage.” This gives a compression to
the inner tube and a slight tension to the outer one. The compression
is so much additional strength to the tube because it must first be
overcome before the powder gases can exert a tension on the inner tube
fibers. The exact amount of the compression and tension for all parts
of a gun at rest or resisting an explosion is a matter of mathematical
calculation. The built-up construction has been used in practically all
our present day types of field artillery.


THE WIRE-WRAPPED GUN.

Wire-wrapped guns consist of:

(a) An inner steel tube which forms a support on which the wire is
wrapped and in which the rifling grooves are cut.

(b) Layers of wire wrapped upon the tube to increase its resistance
by the application of an exterior pressure as well as to add to the
strength of the structure by their own resistance to extension under
fire.

(c) One or more layers consisting of a steel jacket and hoops placed
over the wire with or without shrinkage. The jacket generally furnishes
longitudinal strength to the guns, and the breech block is screwed into
the jacket, or into a breech bushing, which is screwed into the jacket.

The principal advantages of this type of gun over the built-up is
economy of manufacture and greater facilities for inspection of
materiel in the layers over the tube. The wire wrapping has itself
a large reserve of strength due to the high elastic limits that may
be given it. Two methods are used to wrap the wire: (a) at constant
tension (b) at varying tension so that when the gun is fired with the
prescribed pressure, all layers of wire shall be subjected to the
same tangential stress. The latter method is theoretically better, but
because of the ease of manufacture, together with the large factor of
safety possible, the wire is usually wrapped at a constant pressure.


THE BUILT-UP GUN.

All army guns except small howitzers or mortars are of the built-up or
wire-wrapped type. Built up guns of less than 5” caliber, or howitzers
up to 8” caliber consist of an inner tube and a jacket shrunk onto this
tube. The jacket covers the breech end of the gun and extends forward
to the center of gravity. Built-up guns of larger caliber have one more
layer of hoops in addition to the jacket, one layer of hoops usually
extending to the muzzle.

The bore of the tube forms the powder chamber, the seat for the
projectile and the rifled bore. Rifling consists of a number of helical
grooves cut in the surface of the bore. The soft metal of the rotating
band of the projectile is forced into these grooves causing the
projectile to take up a rotary motion as it passes through the bore.
This is necessary in order to keep the projectile stable in its flight.


TWIST.

By twist of rifling is meant the inclination of one of the grooves to
the element of the bore at any point. Rifling is of two kinds: (a)
Uniform twist, or that in which the twist is constant throughout the
bore, (b) Increasing twist or that in which the twist increases from
the breech towards the muzzle.

The twist of rifling is usually expressed in the number of calibers
length of bore in which it makes one complete turn. The twist actually
required at the muzzle to maintain the stability of the projectile
varies with the kind of projectile and the muzzle velocity. If a
uniform twist be used, the driving force on the rotating band will be
at a maximum when the pressure in the guns is at a maximum—or near
the origin of rifling (seat of the projectile). The increasing twist
serves to reduce the maximum driving force on the band thus lessening
the danger of stripping the band. This is its principal advantage over
the uniform twist, though it also reduces slightly the maximum pressure
in the gun. The principal disadvantage of the increasing twist is the
continued change in form of the grooves pressed in the rotating band,
as the projectile passes through the bore. This results in increased
friction and a higher value for the passive resistance than with a
uniform twist. (Note: greater ranges obtained by cutting grooves in
projectile, principal used on the long range gun by the Germans.) If
the twist increases from zero at the breech uniformly to the muzzle,
the rate of change in the tangent to the groove is constant. A twist in
this form offers less resistance than the uniform twist to the initial
rotation of the projectile. To still further diminish this resistance a
twist that is at first less rapid than the uniformly increasing twist
and later more rapid has been generally adopted for rifled guns.

Formerly in our service the twist was uniform; one turn in 25 calibres
for guns and one turn in 20 calibres for howitzers. All the latest
model army guns, however, have an increasing twist of one turn in 50
calibres at the breech to one turn in 25 calibres at a point from 2
to 4 calibres from the muzzle. In howitzers and mortars the twist is
sometimes one turn in 40 calibres at the breech to one turn in 20
calibres at a point several calibres from the muzzle. Some mortars are
rifled with a uniform twist and some guns have a rifling which begins
with a zero twist. (The 1905 3” gun, 0 to 1 in 25.)


OUTER CYLINDERS.

Outside of the tube is the jacket. It extends to the rear of the tube
a sufficient distance to allow of seating the breech block. In this
manner the longitudinal stress due to the pressure of the powder gases
on the face of the breech block is transmitted to the jacket thus
relieving the metal of the tube from this stress. In all built-up guns
there is some method devised for locking the tube to the jacket so as
to prevent relative movement of these parts.

Considering the gun alone the greatest range is obtained at an angle of
about 43 degrees from that gun which fires the heaviest projectile with
the greatest velocity. The caliber being limited to from 2.95 inch to
3.3 inch, the projectile is limited in weight to from 12 to 18 pounds.
The weight of the gun is limited to between 700 and 1000 pounds and in
length to between 27 and 36 calibers. The longer the gun, the greater
the weight and velocity from the same charge of powder. A pressure of
33,000 pounds per square inch with a corresponding velocity of 1700
f. s. has been found to be as high a pressure and velocity as are
desirable for a reasonable length of life for a field gun, the average
life of which is 10,000 accurate rounds.

Under the French school of artillery, which dominates our service at
present, our bore is 75-mm, the weight of our shell 12 pounds, our
shrapnel 16 pounds, the velocity for the one about 1,750 f. s. and for
the other about 1,680 f. s.


BREECHBLOCKS.

The breechblock appears in four distinct types. Our own service has for
years used the swinging interrupted screw breechblock which in the 1905
model is the equal of any of that type in existence. The swinging block
has serious disadvantages for high angle fire in that it requires an
excessive amount of room to operate and is difficult to load at high
elevations.

The Italians have introduced a new breechblock in one of their recent
guns, consisting of a half cylinder with superimposed spherical face
on its cylindrical surface rotating vertically about a horizontal
axis perpendicular to the axis of the bore. The gun is loaded through
a groove in the breechblock when the latter is in its horizontal
position. The block, which is semi-automatic, is very satisfactory. It
is adapted to high angle fire.

The French in their “75” have used the rotating eccentric screw type,
which is rapid in movement and lends itself fairly well to high angle
fire. It is completely enclosed and of rugged construction.

The Germans have used the sliding wedge type of block, moving in a
horizontal direction, which does not lend itself to high angle fire.

The United States in its recent field carriage adopted the sliding
wedge type in a vertical plane on account of its manifest superiority
in fire at high angles. This block is rather difficult to manufacture
and the type has a tendency to stick. The automatic closing
necessitates a strong closing spring which fatigues the block operator,
No. 1 in the gun squad. It is interesting to note that in a prospective
new design for the 1916 gun carriage the American Ordnance Department
adopted the French breechblock; and the St. Chamond Company, designing
for the American Expeditionary Forces, adopted the American drop block.

Requirements for a breech mechanism:

The following may be said to be the principal requirements for a
successful breech mechanism.

1. _Safety._ To be safe: (a) the gas must be restrained from escaping
to the rear; this sealing or obturation must be automatic, greater
pressure insuring better obturation. (b) The breech of the gun must
not be weakened by the fitting of the breech mechanism. (c) The parts
must have ample strength to prevent any portion from being blown to the
rear. (d) The danger of premature discharge must be minimized. (e) The
breechblock must be securely locked to prevent opening on firing.

2. _Ease and Rapidity of Working._ Otherwise, rapid and continuous fire
cannot be maintained. Hence this would include facility in loading and
certainty of extraction for rapid fire guns.

3. _Not Easily Put Out of Order._ In other words it must be able to
meet service conditions and hard usage. Parts should have a reserve
strength.

4. _Ease of Repair._ Parts most exposed to wear should be so designed
as to permit being replaced. This will also include accessibility to
parts, so that breakage of a part will not disable the mechanism for a
long time.

5. _Interchangeability._ Not only should individual parts be made
interchangeable by accurate workmanship, but the whole mechanism should
be capable of being mounted on similar guns. This is to meet service
conditions.


GUN CARRIAGES.

A modern gun carriage is expected to stand steady on firing, so that
in the first place it requires no running up, and in the second place
it maintains the direction of the gun so that only a slight correction
in elevation and direction is required after each round. The carriage
is maintained in position by the spade, which sinks into the ground,
and by the friction of the wheels upon the ground. If the force of the
recoiling gun were communicated directly to the anchored carriage the
effect would be to make it jump violently, which would not only disturb
the lay, but would prevent the cannoneers from maintaining their
position. The hydraulic recoil brake is therefore interposed between
gun and carriage. If the guns were rigidly attached to the carriage
the latter would be forced back a short distance at each round, and
the whole of the recoil energy would have to be absorbed in that short
motion. Instead of this the gun alone is allowed to recoil several
feet and although the recoil energy is in this case greater than it
would be if gun and carriage recoiled together yet it is so gradually
communicated to the carriage that instead of a violent jerk we have a
steady, uniform pull, the only effect of which is to slightly compress
the earth behind the spade. In a well designed carriage the amount of
this pull is always less than that required to lift the wheels off the
ground by rotating the carriage about the spade.

The only motion of the carriage which takes place is that due to the
elastic bending and rebound of its parts under the cross strains set
up on discharge. These strains are inevitable since the direction of
recoil cannot be always exactly in the line of the resistance of the
earth behind the spade. This movement of the axis is known as jump
and must be determined by experiment for the individual piece in its
particular mounting.

The principal parts of the typical gun carriage are the cradle, a
device for mounting the cradle—called in the different models rocker,
pintle yoke, and top carriage, the trail, the wheels and axle. The gun
slides in recoil on the upper surface of the cradle and the cradle
contains the recoil controlling parts.

In the design of the carriage the constructional difficulty lies not
so much in preventing the carriage from recoiling but in preventing
the wheels from rising off the ground on the shock of discharge. The
force of the recoil of the gun, acting in the line of motion of the
center of gravity of the recoiling parts, tends to turn the carriage
over backwards about the point of the trail or center of the spade.
This force is resisted by the weight of the gun and carriage, which
tends to keep the wheels on the ground. The leverage with which the
overturning force acts is due to the distance of its line of action
above the center of the spade; the leverage with which the overturning
force acts is that due to the horizontal distance of the center of
gravity of the gun and carriage from the center of the spade.

It follows that the steadiness of the carriage for a given muzzle
energy may be promoted by four factors.

(a) Increasing the weight of the gun and recoiling parts. This reduces
the recoil energy.

(b) Increasing the length of recoil allowed. This reduces the
overturning pull.

(c) Keeping this gun as low as possible either by reducing the height
of the wheels, or by cranking the axle downwards. This reduces the
leverage of the overturning force.

(d) Increasing the length of the trail. This increases the leverage of
the steadying force.

The well designed gun carriage is one that combines these factors in
a practical way so as to give the greatest possible steadiness to the
carriage at the same time keeping within the limits of weight imposed
by the necessity of mobility.

Gun carriages are constructed so as to permit movement of the tube in
the vertical and generally in the horizontal plane. These two motions
may be made simultaneous if so desired by proper combination of the
two motions and the axis of a gun aligned in any desired direction
within the limits of motion of its mount. The two motions referred to
are designated as follows: (a) Rotation of the piece about a vertical
axis, its inclination with the horizontal remaining unchanged is
called “traverse.” (b) Movement of the piece in a vertical plane,
the direction of the horizontal projection of the axis of the bore
remaining unchanged is called “elevation.”

In order to permit of the two motions mentioned, gun carriages are
provided with mechanisms for giving the piece accurately controlled
motion in both elevation and traverse. The elevating gear of most
American guns is an application of the Chinese or Telescopic screw.
This gives a short assembled length with the necessary extended length
required for modern ranges. It also gives the necessary rapidity for
action. An entirely different mechanism is used in our howitzers and
American 75s. In this case motion is communicated to the rockers, which
carry the gun and cradle, through the engagement of worms with teeth
cut on the lower circular edge of the rockers, the latter being pivoted
on the cradle trunnions.


TRAVERSING MECHANISMS.

Movement of the gun in traverse is accomplished in two general ways.

(=a=) Pivot on the gun carriage axle.

1. The gun and cradle move around a vertical pintle or pivot placed
in a saddle or rocker which itself pivots on horizontal trunnions or
bearings usually attached to the axle. The rear end of the rocker forms
a seat or bearing on which the cradle and gun move in traverse. The
upper end of the elevating screw is also attached to the rear end of
the rocker. This allows the rocker and cradle to be moved together in
elevation and the cradle to move on the rocker in traverse.

2. The gun and cradle are mounted by means of horizontal cradle
trunnions on a top carriage. The top carriage moves in traverse around
a vertical pintle or bearing attached over the axle and between the
front end of the trail flasks. The rear end of the top carriage moves
on bearings attached to the top of each side of the trail flasks. This
allows the gun, cradle and rocker to move in elevation with respect to
the top carriage and the top carriage bearing the gun, cradle rocker
and elevating mechanism to move in traverse with respect to the bottom
carriage.

(=b=) The gun, cradle and trail move in traverse by sliding along the
axle of the carriage on bearings provided for that purpose. In this
case the trail spade is the point of pivot.

The first system is the one generally used on all American gun
carriages except the 155-mm Howitzer. It gives ease and speed in the
manipulation of the piece in traverse, but has the disadvantage of
rendering the carriage less stable in firing due to the fact that
the direction of recoil of the gun is in the direction of the line
joining the trail spade and the central pivot, _only_ when the gun is
absolutely in the center of its traverse. In all other positions, which
will be the usual case, there is a component at right angles to the
line of trail spade-central pivot which tends to throw the gun off from
its proper direction making it necessary to relay each time the gun is
fired. The second method is that in use on the French 75-mm gun and the
French and American 155 howitzer. While not so easy of manipulation and
giving less freedom of movement in traverse (about 106 mils) it still
has the advantage in that it gives greater stability in firing due to
the fact that the gun always recoils along the line through the trail
spade, perpendicular to the axle.


ELEVATING MECHANISMS.

There are two general classifications of gun carriages according to the
manner in which the laying for elevation is effected. The 3” gun is
an example of one type in which the total quadrant angle of departure
is laid off as one angle necessitating at each resetting of a range a
new resetting of the range bubble. It is evident that this militates
against both speed and accuracy in laying for elevation. The other type
is illustrated by the American 75 and by the French and British 75-mm
gun carriages which have what is called the “independent line of site.”
It differs from the other type in that there is placed between the top
carriage and the cradle an intermediate carriage or rocker arm pivoting
on the gun trunnions at one end, and carrying at the other the support
for the elevating device which gives to the cradle and the gun the
proper elevation for the range. This intermediate carriage or rocker
arm has a toothed edge geared with a pinion fastened to the trail
flask, by means of which, gun cradle and elevating device may be moved
in elevation without disturbing the relation between itself and the
gun, this being done by gears independent of the elevating mechanism.
An angle of site may be set off for the intermediate carriage and after
the bubble is centered this actuating pinion may be blocked and no
further concern be paid to the angle of site. A cannoneer therefore has
only to set his range accurately on the index to give the changes in
range ordered.

Elevation is accomplished by telescoping screws, by circular racks and
pinions, and by worms and arcs. Telescoping screws are good for from
15 to 20 degrees in elevation only, as for greater angles they become
rather too large and cumbersome. The elevating arc is attached on the
top, on the bottom or on the side of the cradle and, if possible, at
its center. When the latter is not possible, two arcs are generally
used to prevent torsional strains developing. Top racks are exposed to
fire, side circular racks or arcs interfere with the traverse, with the
placing of the sights, and with the general handling of the carriage.
The bottom of the cradle is perhaps the best location for the rack. As
in the traversing mechanism, a train of bevelled gears transmits the
power from the hand wheel to the elevating mechanism.

In both the traversing and elevating mechanism, strength, simplicity,
power, accessibility, non-interference and absence of lost motion are
the features sought. To secure these is one of the most difficult
things in gun-carriage design; for, since the traversing and elevating
are the last two elements considered, they must, therefore, be the
ground for modification and the means of adapting the great main
elements—namely, wheels, axle, trail, recoil mechanism and gun—into a
unit.


RECOIL MECHANISM.

The recoil system of the gun carriage consists of a recoil brake, a
counter recoil mechanism and a counter recoil brake. The function of
each part is apparent from its name. Various systems of checking recoil
on field guns have been used, among them may be mentioned; friction
devices including brakes on the wheel, inclined planes, pneumatic and
hydraulic brakes. All have either been superseded by the last named or
are used in connection with hydraulic brakes. The power of the brake
lies in the pressure produced in the cylinder through the resistance
to motion offered by the liquid flowing through apertures. By varying
the size of these apertures the braking effect may be controlled so
as to fulfill the conditions demanded by the service. In designing
the brake, the effect of the counter recoil system, angle of fire,
length of recoil, friction and pressure within the cylinder must all
be considered. In howitzers which are designed to be fired at high
angles of elevation, the recoil must be shortened to prevent the breech
striking the ground, a condition successfully met. Since the pressure
due to recoil is ultimately led into the ground through the trail and
spade, consideration must be given to the problem of the moment of
inertia about the trailspade. The tendency to turn over backward about
the spade as the center is offset by the amount of the weight of the
carriage with respect to the same point. This raises the question as to
how much pressure may be allowed to act to the rear; all of which must
be considered in designing the carriage. The counter recoil systems in
general use are two: spring or pneumatic. The former is illustrated in
our 3” and 75-mm field guns, the latter by the French 75-mm gun and
155-mm howitzer. Their purpose, of course, is to return the gun “into
battery” after it has recoiled on the carriage.

The recoil mechanism is a study in itself, of which there are two
schools—the advocates of the spring and of the air recuperators. Great
Britain, Germany and the United States have been the advocates of
spring recuperation and France of air recuperation. Great Britain and
the United States were of the spring school, undoubtedly, because of
the lack of a satisfactory air recuperating system; which is rather
strikingly proven by the fact that both countries have adopted air
recuperation since they have procured or developed satisfactory types.

Both schools have grounds for their position, however. The spring
school has in its favor simplicity of design and manufacture and ease
of replacement, which can be done in the field. On the other hand,
spring recoils have many breakages and greater weight combined with a
high replacement of weakened springs, the life varying from 3000 to
8000 rounds.

The air school has in its favor a high order of efficiency—smoother
action, general all around efficiency and less weight. But the air
recuperator is difficult to manufacture, costly, and when damaged must
go to the rear to be repaired; which, however, it seldom needs.

In mounting the spring recuperator, the most recent practice has
separated the recoil mechanism from the springs in order to distribute
the piston rod pull, thus preventing whip and allowing easy access to
the various parts for replacement, refilling and repairs. In order to
lower the center of gravity, the gun is slung under the recoil cylinder
with the two spring recuperators below and on either side.

Air recuperators are invariably located below the gun for protection
and because of their large size and shape, which adapt them for
attaching the elevating mechanism.

[Illustration: BATTERY OR FIRING POSITION

IN-BATTERY OR FIRING POSITION

HYDRO-SPRING RECOIL SYSTEM

HYDRO-PNEUMATIC RECOIL SYSTEM WITH FLUID IN DIRECT CONTACT WITH THE
AIR]

In either system, the recoil is taken up by means of oil or glycerine
and water passing through an orifice created by a slotted piston
passing over ribs of varying height, or through a valve on the pressure
side of the piston, or by a solid or perforated piston passing through
a perforated intermediate cylinder.

The latter type is particularly adapted to variable recoil guns as the
intermediate cylinder can be rotated, thus throwing varying orifices
into position for the flow of oil.

Counter recoil is accomplished by the springs or by the air pressure in
the hydro-pneumatic system, in which the air pressure is sufficient to
hold the gun in battery at all elevations and is built up at recoil.

In all counter recoil systems, it is necessary to insert a buffer to
take up the remaining energy of the springs or air pressure so as to
bring the gun into battery without appreciable jar. Numerous types have
been developed and perfected.

The counter recoil brake or buffer in our 3”-gun is a slightly tapered
bronze rod, tightly fitting in the cylindrical bore of the piston rod.
The retardation caused by forcing the oil in the piston rod out through
the small clearance between the buffer and bore of the piston rod eases
the return to battery without jar to the gun, which has been forced
back by the counter recoil springs.

The physical law that action and reaction are equal has a peculiar
emphasis when applied to the firing of a piece of high powered
artillery. The force exerted to throw a heavy projectile 7 miles or
more from the muzzle of the gun is toward the breech of the weapon in
its recoil. How some of these forces are handled safely and easily by
mechanical means are almost beyond the mind’s grasp. Not long ago a
touring car, weighing two tons, traveled at the rate of 210 miles an
hour along a Florida beach. Conceive of such a car going 337 miles an
hour—which is much faster than any man ever traveled; then conceive of
a mechanism which would stop this car, going nearly six miles a minute,
stop it in 45 inches of space and one-half a second of time without the
slightest damage to the car. This is precisely the equivalent of the
feat performed by the recuperator of a heavy howitzer after a shot.


SHIELDS.

Although cover for the cannoneers had been used off and on since the
invention of guns, it had fallen into disuse until it was firmly
established as an essential feature by the French on their 75-mm
in 1897. All modern field guns have such protection both for the
cannoneers and for the delicate parts of the material which would
be damaged by shrapnel balls or shell fragments. The shield is made
of hardened steel capable of withstanding the impact of a bullet
of a service rifle at a 100 yds. range at a standard velocity. For
convenience the shield is divided into three parts known as the top
shield, main shield and apron, with suitable ports equipped with
shutters for the line of vision from sights. The main is fastened to
the axle and is rigid. The apron is hinged to the main shield or the
axle-swinging forward for the traveling position. The top shield is
fastened to the main shield by hinges and swings forward and downward
for traveling position.


SIGHTS.

The sights serve three important functions. They improve the vision of
the gunner and lay the gun in elevation and direction. The simplest
sight is the one over the line of metal which lays for direction only,
the second is the tangent sight mounted on a range arc centered on the
axis of rotation in elevation usually having a deflection scale to
correct for drift and to lead the moving target. This unit lays for
range and direction. The last sight is the telescopic or panoramic
sight which is mounted on a range arc and lays for direction only,
it is the unit for indirect fire, laying for direction, and markedly
improving the vision of the gunner. The latest model of the American
panoramic sight is superior to any in existence.

For precision in indirect fire, practically all carriages are equipped
with some form of range quadrant, containing a means of setting off
the angle of site and the range angle. All instruments are equipped
to compensate for difference in wheel level. The British carriage
automatically corrects for deviation, simplifying the firing date by
that element.


WHEELS.

The height of the wheels affects the draft, weight, clearance, and
stability of the carriage both as to road stability—i. e., low center
of gravity; and firing stability—i. e., the overturning movement
about the end of the trail. It is now believed that entirely too much
stress has been laid on road clearance. Reducing the height of wheel
reduces the weight and road clearance, lowers the center of gravity and
increases the firing stability; but it also reduces the angle of gun
elevation unless the trail is shortened. Firing stability in general is
increased by adding to the weight of the gun, lengthening the recoil,
slinging the gun as low as possible and lengthening the trail. The less
the height of the wheel exceeds four feet the better, despite the poor
draft feature, which is compensated for to some extent by a reduction
in weight and turning radius.


AXLES.

Axles are straight or of the offset type. The straight axle is stronger
for its weight. The drop axle allows the center of gravity to be
lowered.


TRAILS.

Most modern trails are of the sectional built-up type. Some, however,
are of tubular and telescopic. The most variable portion of the trail
is the spade. It consists of two parts, the spade proper and the float.
The former prevents recoil, the latter the burying of the trail. The
spades proper are of three types: the fixed, as in the French 75-mm;
semi-fixed, as in the 155-mm howitzer; and driven, as in the Deport and
American 1916 75-mm. Each has advantages and disadvantages. The driven
spade is considered essential for the split trail carriage, as the
latter has no means of seating itself; and should one spade take, and
not the other the carriage might be damaged when the gun is fired at an
extreme traverse.

Split trails introduced a novelty in field gun carriages, in that a
compensating device became necessary to adjust for the difference in
ground level of the two spades.


CONCLUSION.

Guns are designed to function in a certain way. They are not
temperamental. They follow absolutely and certainly fixed mechanical
laws. If they fail there is a reason and it can be remedied. Certain
parts are given certain shapes and forms, are machined to nice
adjustments, and in taking down and assembling them, brains and
dexterity are the tools to use rather than force and sledge-hammers.
Learn from your text when and how to apply force and above all when not
to use it. Treat these guns as you would a friend on whom you know you
can depend. They will not fail you.




CHAPTER IV

MODERN ARMAMENT.


THE ARTILLERY OF A FIELD ARMY; ITS FUNCTIONS.

The artillery assigned to a field army should be of such mobility,
power, variety and number as to insure the success of its purpose and
to enable this success to be gained with the minimum of casualties.
The latter point must receive careful consideration in studies of
organization, for without adequate artillery preparation and support
the successes of the most gallant infantry can in a series of actions
become little more than pyrrhic victories. Many actions of our
divisions in France resulted in casualties whose numbers decreased in
proportion to the number of guns with which divisions were supported.
The proportion of guns to the thousand gross strength of infantry,
cavalry, and machine guns adopted by the armies of the first class
powers before the opening of the present European War in 1914 was:

British, 6.8; French, 4.6; German, 6.4; American 3.2 (Greble Board).

During the war this proportion was constantly increased until at the
close under conditions of position or entrenched warfare it was between
8 and 12 per thousand; this varied of course with the activity in
different sectors. In quiet sectors and under conditions of maneuver,
or open warfare, which necessitated leaving much artillery behind, it
was about 6 per thousand.

A program of types of artillery weapons should be founded on the object
and the means—that is, the destruction of the target and the projectile
to accomplish this. In the study of an artillery program there are two
methods of approaching the subject. First, by starting with a minimum
weight of projectile and working up to a reasonable maximum, according
to some law and taking the corresponding calibers, a theoretical series
of guns and howitzers can be expressed. For instance, if the law be
doubling the weight of the projectile the series of types could be:

  Projectile of   13 pounds, caliber  3”.
  Projectile of   26 pounds, caliber  4”.
  Projectile of   52 pounds, caliber  5”.
  Projectile of  104 pounds, caliber  6”.
  Projectile of  208 pounds, caliber  8”.
  Projectile of  416 pounds, caliber 10”.
  Projectile of  832 pounds, caliber 12”.
  Projectile of 1664 pounds, caliber 14”.

The second and more logical method, and one followed in our service,
is to consider the artillery missions and determine the types best
suited irrespective of any theoretical series of weights and calibers.
However, in the discussion of artillery missions and the proper types
for their fulfillment there is a remarkable degree of unanimity of
thought on these subjects; and the above table actually contains, with
slight variations, the types that are most strongly recommended. While
granting the great variety of artillery missions that often shade into
each other, it is believed that they can best be considered in three
great classes that follow the tactical composition of a field army:
those of division, corps and army artillery.


DIVISION ARTILLERY.

=Missions.= The division artillery, first of all, must have the
mobility that will permit it to accompany the infantry of a division
and the maximum power consistent with that mobility; its object must
be primarily the infantry of the opposing division. It is therefore
bound to its own infantry with the closest bonds and its tactical use
cannot be separated from that of the infantry. The division artillery
must fire, accurately, a man killing projectile and be prepared for
quick changes of targets; it must have a great range because of depth,
both of its own and the enemy division; it must continually harass
the enemy, prevent his movement and force him into cover or protected
trenches. On the defensive it must break up the opposing infantry
formations by preparing a counter-offensive fire and by annihilating
fire on points from which the enemy attacks emerge; and, failing in
these, be prepared to use the barrage and shrapnel fire at close range.
In the offensive the division artillery must play its part in the
complex schemes of artillery preparation by cutting wire, destroying
machine gun nests, gassing areas, concentrating on infantry positions
and taking the principal part in the deep barrage that should precede
the infantry attack. Its fire, accompanying the infantry movement,
requires its own movement and by its mobility it often becomes for some
time the sole artillery protection in the preparation and holding of a
position which has been taken.

=Light Gun and Howitzer.= The consensus of opinion of artillery
officers is that the division artillery missions are best fulfilled by
a light field gun and a light field howitzer having a range of at least
11,000 yards. While differing in mechanical features, the field guns
of the different European countries are practically of the same type
and, though constant effort is being made to improve details, they can
be stated as generally satisfactory to their own governments and not
liable to any radical changes. The general type of field gun, while
capable of fulfilling most of the division artillery missions, must be
supplemented by a proper howitzer. There are many instances where the
terrain or the lay of the land offers such protection to the infantry
that the field gun cannot bring an effective fire. The howitzer has
the great advantage that with the proper set of propelling charges
and, therefore, choice of trajectories for the same range, protected
positions can be chosen for howitzers that guns could not use, and
angles of fall obtained on objectives that the normal ammunition of
guns would not give. The low muzzle velocity of howitzers admits of
their almost continuous use in harassing fire and allows the use of a
projectile double the weight of that of a field gun. Such a howitzer
renders excellent service in wire cutting and is a useful projector of
gas shells. To insure the mobility required of all divisional artillery
the weight of the howitzer and carriage should not exceed that of the
field gun, or about 4,500 pounds.

=Light Gun Discussion.= The consensus of opinion of all artillery
officers—French, English and American—is that the 75-mm gun, or
approximately this caliber, firing a 15-pound projectile or a
projectile of approximately this weight, and having a range of not less
than 11,000 yards, is a satisfactory weapon at the present time for
use with the division artillery. The projectile in question, whether a
shrapnel or a high explosive shell, satisfies adequately the criterion
of man-killing. At the close of the war the nations were not entirely
in accord with respect to their conception of an up-to-date carriage
for a light field gun. All the nations whose tendencies have been
considered in this report have experienced to a varying degree with
field gun carriages, particularly in a desire to design a carriage
permitting a greater angle of elevation and greater movement of the gun
in the traverse. The Italians have expressed themselves in the modified
Deport Carriage; this vehicle is of the split trail type and permits
an elevation in excess of 75 degrees, and a traverse on each side of
the center of the carriage of about 20 degrees—about 356 mils. Up to
the time that the board left France it was not possible to learn the
French decision in the matter of a split trail carriage for their light
field gun. It is known, however, that several types of this carriage
have been designed and tested; it is known, also, that considerable
favor has been found with the American 1916, which type has been tested
under the auspices of the French Government. In England, however, the
board was not able to develop any enthusiasm for the split trail type,
although the matter had been seriously considered. In that country
the up-to-date field gun carriage appears to be adequately expressed
in their new 18-pounder. The vehicle upon which this gun is mounted
permits an elevation of 37 degrees and an axle traverse of 4½ degrees
on each side. The trail is a box trail and the carriage is simple and
steady in its construction and lends itself to rapid production.

=Motorization.= At some time in the future it is probable that all
the division artillery will be motorized. The result of such a change
in the prime mover would be to remove the present restriction as to
weight of gun and carriage. The board senses a demand in the near
future for a light field gun having a maximum range of approximately
15,000 yards; such a range may be achieved by increasing the muzzle
velocity and, perhaps, the weight of the projectile, although change
in the form of projectiles will give some improvement over the present
ranges. It is probable that the limiting features in the design of
field guns of the future will be the requirement that it should pass
safely over temporary pontoon bridges and that the weight and form and
size of ammunition must be such that the present rate of fire will
not be slowed down. The board is of the opinion that, except as to
perfection of details, the limit of carriage design, as expressed by
the most modern type of box-trail and split-trail carriages, has been
reached; and feels that with the advent of motor transportation the
tendency will be toward a gun mounted on a self propelling carriage and
expressing the desires of the field artillery with respect to maximum
horizontal and vertical arcs of fire.

=Light Gun. Ideal.= A gun of about 3” caliber on a carriage permitting
a vertical arc of fire of from 5 degrees depression to 80 degrees
elevation and a horizontal arc of fire of 360 degrees; a projectile
weighing not over 20 pounds, shrapnel and high explosive shell of
satisfactory man-killing characteristics with maximum range of 15,000
yards; fixed ammunition, smokeless, flashless propelling charge; time
fuse for shrapnel. With shell having safe fuses with different lengths
of delayed action after they land. The high explosive shell should
be of one type only. Two propelling charges should be furnished, a
normal charge for about 11,000 yards range and a super charge for
maximum range. The proportion should be 90% of the former and 10% of
the latter. A maximum rate of fire of 20 rounds per minute is deemed
sufficient.

=Light Gun. Practical.= For the present, arm brigades with 75-mm
materiel. Models 1916, 50%, and 1897 (French), 50%.

=Transport. Ideal.= Mechanical transport is the prime mover of the
future. The introduction of mechanical transport will undoubtedly cause
far-reaching changes in the types of gun carriages. It is not possible
now to state just how far this will go or whether a gun mounted on a
self propelled vehicle or one mounted on some type of trailing vehicle
will be the final result. Both types may be necessary. It is urgent
that study and development be carried along these lines, as we are on
the verge of changes fully as radical as the introduction of the long
recoil field gun and carriage, and the country first utilizing the new
capabilities opened up by mechanical traction and the caterpillar will
have a great advantage in the next war. A limit of 4,500 pounds behind
the team has heretofore been imposed on the artillery of this class.
The corresponding limit in the future will probably be that imposed by
pontoon bridges.

=Transport. Practical.= Therefore it is thought that four regiments
of 75-mm guns (two regiments of French Model 1897, and two regiments
of U. S. Model 1916) should be immediately equipped with motors, the
remainder to be horsed; mechanical transport to gradually replace horse
only after the tractor demonstrates its superiority in service.

=Light Howitzer Discussion.= The consensus of opinion of American
army officers consulted is that a howitzer about 4” in caliber,
firing a projectile weighing from 25 to 30 pounds at a maximum range
greater than 10,000 yards, is required. This opinion is concurred in
by the French, Italians and English, and it appears to be definitely
established that the mobility of the light field howitzer should be
practically the same as that of the light field gun. The British
army was equipped with a 4½” howitzer, firing a projectile weighing
35 pounds and with a maximum range of 7,700 yards; the weight of the
howitzer limbered is 4676 pounds—150 pounds more than the weight of the
18-pounder field gun. No evidence was found that the British Government
intended making any alterations in the design of this howitzer;
naturally they will attempt to increase the range, power and accuracy
of the projectile by change in its weight, its capacity and its form.
The French artillery was not equipped with the light field howitzer
of approximately the same weight as the 75-mm field gun. During the
war it was found impracticable to construct a lighter howitzer without
interfering with the production of other calibers which were considered
more important. In the earlier stages of the war the Italian artillery
was not equipped with a light field howitzer; however, before the
end of 1917 orders were placed for several hundred howitzers of the
105-mm type. It should be noted that several hundred howitzers of this
caliber were being constructed before the armistice and that many have
been captured from the Austrians by the Italians; this, so far as the
Italians were concerned, makes it certain that a light field howitzer
will be furnished by the Italian army. The German and Austrian armies
were equipped with a howitzer of the light field type; this weapon had
a caliber of 105-mm type.

It fired a projectile weighing 34.54 pounds at a maximum range of
10,500 yards. (Streamline shell.) The weight of the howitzer limbered
was 4,500 pounds. In the opinion of the board, the Germans have
proceeded on sound principles in their development of the light field
howitzer. Their ’98 model was a companion piece to their ’96 field gun
and in the years that passed from 1898 to 1916, which included their
early war experience, they kept to the idea of the relation of the two
pieces even to the extent of including in a field artillery regiment
one battalion of light howitzers. Their 1916 models of both light gun
and howitzers show the endeavor to keep the pieces in the same class;
that is, the weight of the gun and howitzer in action nearly the same,
2,750 pounds and 2,700 pounds; the weight of the gun limbered and the
howitzer limbered are the same, 4,500 pounds; the elevation of both the
same—minus 10 to plus 40 degrees; the carriages are of the same type;
and the extreme ranges of gun and howitzer are respectively 11,700 and
10,500 yards. From the foregoing it is seen that all the important
belligerents except the French and the Americans were equipped with
a light field howitzer firing a projectile about twice the weight of
the light field gun projectile and having otherwise the same general
characteristics. There is no evidence to show that the fire of the
French and the American artillery was not fully effective as that of
any other artillery; however the testimony of the French and American
artillery officers is to the effect:

(a) That the lightest howitzer in use, i. e., the 155-mm, was not
sufficiently mobile to be a suitable companion piece for the 75-mm gun.

(b) That many times the fire of the 75-mm gun proved ineffective due to
its flat trajectory; a howitzer would have been more effective in the
attack of certain targets.

(c) That a large volume of fire is necessary.

(d) That while the 155-mm howitzer is more powerful than the light
field howitzer its consumption of ammunition for many purposes is
wasteful and extravagant and its volume of fire is insufficient.

(e) That the light howitzer is particularly suited for the destruction
of wire entanglements; its better accuracy and more powerful projectile
make it more suitable than the field gun for that purpose.

(f) That the 75-mm field gun projectile is not so satisfactory a gas
shell as the howitzer projectile which has greater weight.

=Light Howitzer. Idea.= A weapon of about 105-mm caliber on a carriage
permitting a vertical arc of fire from minus 5 degrees to plus 65
degrees, and a horizontal arc of fire of 360 degrees. Efforts should be
made to develop a carriage which can be used interchangeably for the
division light gun referred to above and this howitzer. The projectile
should weigh about 30 to 35 pounds and should include both shell
and shrapnel. A maximum range of 12,000 yards will be satisfactory.
Semi-fixed ammunition with varying charges should be used, otherwise
the ammunition should be similar to that provided for the 75-mm guns.

=Light Howitzer. Practical.= For the present, the division should be
armed with the 155 howitzer, Schnieder, but active development and
test should be made on a type as stated under “Ideal” above, and with
the ammunition and other accessories to it. Upon the development of
the carriage as nearly approximating the ideal as may be practically
possible, efforts should be made to secure quantity production in
order that it may be incorporated in the division as recommended. In
addition, a split trail carriage for this howitzer should be developed.

=Transport.= The light howitzer should have the same means of transport
as the light field gun and the same remarks heretofore made as to the
probable future development of the field gun also apply to the howitzer
carriage.


CORPS ARTILLERY.

=Missions.= It will be noted above that the division artillery missions
did not include their own protection against the enemy artillery. This
counter-battery work is the principal mission of the corps artillery.
The corps artillery has also the mission of extensive harassing and
interdicting fire along the corps front and to a greater depth than the
capabilities of the division artillery; also of destructive fire on
strong points as well as on railroad facilities and points of supply.
For the accomplishment of these corps artillery missions there are two
types of artillery necessary, a gun and a howitzer, each having 16,000
yards range and each weighing with the carriage about 11,000 pounds.
There is another class of artillery called anti-aircraft artillery to
be considered. This is used first in providing anti-aircraft defense
for army zones, for certain areas in rear of armies or along a certain
line of anti-aircraft defense.

=Medium Gun Discussion.= The consensus of opinion of artillery
officers—Italian, English and American—is that a medium gun of about
6” caliber is necessary. The medium type gun furnished to the American
army was the 4.7 (Model 1906). This gun has a maximum elevation of 15
degrees with a corresponding maximum range of 8,750 yards. The British
army was equipped with the 5” gun—the carriage permits a maximum
elevation of 21 degrees and 30 minutes, giving a maximum range of
12,500 yards. The French army was equipped with, to a certain extent,
the 105-mm and the 140-mm gun. The 105-mm gun a maximum elevation of
37 degrees, with a maximum range of 13,900 yards. The 140-mm gun has
a maximum elevation of 30 degrees and, with a high velocity, has a
maximum range of 19,500 yards. The French 105-mm gun is a modern weapon
(1913). The German artillery was equipped with a 105-mm gun (M-1917)
with a maximum elevation of 45 degrees, and a maximum range of 16,000
yards. The German army was also equipped with the 130-mm gun, having
a maximum range of 16,500 yards. The Austrian army was similarity
equipped. The Italians were equipped with a 105-mm gun essentially of
the same characteristics as the French 105-mm M-1913.

=Medium Gun. Ideal.= A caliber of between 4.7 and 5” on a carriage
permitting a vertical arc of fire of from minus 5 degrees to plus
80 degrees; a horizontal arc of fire of 360 degrees. Shrapnel and
shell weighing not over 60 pounds, maximum range 18,000 yards; with
semi-fixed or separate loading ammunition permissible.

=Medium Gun Practical.= Corps artillery should be armed with the
present type 4.7” gun, Model 1906, except that at least one regiment
should be armed with the British type 5”-guns purchased abroad.

=Transport.= All corps guns should be developed for long, rapid hauls.
Similar ammunition vehicles should be developed. The wheels for the gun
carriage should be rubber-tired.

=Medium Howitzer.= In the opinion of the French, Italians, British
and the Americans, the 155-mm howitzer (Schnieder) was conspicuously
successful in the present war. It should, therefore, be retained
as a type. The howitzer and carriage as it stands at present, is a
highly satisfactory and efficient piece of armament. For the future
it is believed that effort should be made to increase the range by
improvements in the form of projectile, and it is believed that
the form of howitzer and carriage should be studied with a view of
obtaining, through modifications, a maximum range of approximately
16,000 yards.

Many batteries of 155-mm howitzers (Schnieder) were motorized in the
American Army in France, and the consensus of opinion is definitely
toward the retention of this form of prime mover. It is interesting to
note that all the important belligerents have settled upon a howitzer
of approximately 6” in caliber, and otherwise essentially of the same
ballistic characteristics as the type in question. The projectile of
this caliber is the smallest projectile which can be called upon to
give adequate mining effect against material targets of semi-permanent
nature. The place of this howitzer is, therefore, determined by
considerations of its destructive ability. It is a splendid destruction
and neutralizing weapon.

=Medium Howitzer. Ideal.= A caliber of about 155-mm on a carriage
permitting a vertical arc of fire of from minus 5 degrees to plus 65
degrees; and a horizontal arc of fire of 360 degrees. The projectile
should not weigh over 100 pounds and should be interchangeable with
projectiles for other guns of this caliber referred to later on. High
explosive shell, only, should be supplied.

=Medium Howitzer. Practical.= The corps should be armed with the 155-mm
(Schnieder) howitzer referred to above. The type of fuses for shell
should be super quick and long delay.


ARMY ARTILLERY.

=Missions.= In addition to the division and corps artillery fulfilling
the missions outlined above there must be additional artillery
available. There are missions of interdiction, neutralization and
destruction which fall beyond the activities or capabilities of
the normal corps or medium field types; there must exist a surplus
of division or corps types, properly transported, for strategic
reinforcements of divisions and corps during such times as the normal
allotment to such units is insufficient; there must be artillery
of special purpose—mountain artillery, trench and super guns and
howitzers. Of the above additional artillery, a type of heavy field gun
and a type of heavy field howitzer are considered normally necessary
in the armament of a field army; the gun should have a range of
approximately 25,000 yards, and the howitzer a range of about 18,000
yards. These weapons are more powerful than the medium field types, add
range to the interdiction and harassing and to the neutralization and
destruction possible with the corps type. Considering the paragraphs
pertaining to divisional artillery and the introduction to corps
artillery _it will be seen that the normal artillery of a field army
can be accomplished by the assignments of two caliber, i. e., two light
weapons, two medium weapons and two heavy weapons—a gun and a howitzer
in each class—and a satisfactory anti-aircraft gun_.

=Heavy Field Gun.= The consensus of opinion of all artillery
officers—British, Italian and American—is that the heavy field gun
should be of approximately 6” caliber and that guns of greater caliber
than this are necessary in limited number for field operations. The
French were constructing 194-mm guns during the latter stages of the
war. It is believed that in developing this type of gun the French
were actuated almost entirely by the necessity for increased range,
since the German 150-mm gun, Model 1916, outranged the G. P. F. by
approximately 5,500 yards. The French have recently made considerable
progress in securing the necessary increase in range with the G. P. F.
All of the principal nations engaged in the war used a heavy field
gun of approximately 6” caliber. This type has given such general
satisfaction that its continuance is assured. The principal mission of
the heavy field gun is harassing and interdiction fire, and for these
uses the 6” projectile is sufficiently heavy. The maximum practicable
traverse and elevation should be provided by the carriage of the heavy
field gun. The G. P. F. carriage has given general satisfaction, but
its wide tread and the excessive time required to occupy a position
are very objectionable features. It is the consensus of all artillery
officers—French, British and American—that the heavy field gun should
be of approximately 6” caliber and with a range in excess of 25,000
yards, with not less than 60 degree traverse, weighing not more than 12
tons, limbered, capable of occupying and leaving a position quickly,
and with a width of tread which does not prevent two-way traffic on
ordinary roads. The Italians differ from this opinion only in that they
are satisfied with a maximum range of 18,000 yards.

=Heavy Field Gun. Ideal.= A caliber of about 155-mm on a carriage
permitting a vertical arc of fire from 0 degrees to plus 65 degrees;
with a horizontal arc of fire of 360 degrees. The maximum range should
be about 25,000 yards.

=Heavy Field Gun. Practical.= Arm with the present type 155-mm G. P. F.
and carry on experiments for type of carriage as outlined for division
field gun. The fuses should be super-quick and short delay.

=Transport.= All artillery of this type should be motorized and tested
and experiments for ammunition vehicles to correspond with the types of
carriages developed, and should be carried on simultaneously.

=Heavy Field Howitzer.= No type of heavy field howitzer developed
during the war has given general satisfaction. The consensus of all
army artillery officers—French, English and American—is that two
calibers of howitzers are necessary—one a companion piece for the 6”
gun and one of the maximum possible power consistent with the necessary
mobility. The lighter of these two howitzers should have the same
mobility as the 6” gun, with a caliber of about 8” and a maximum range
of not less than 16,000 yards. The heavy field howitzer should be of
about 9.5” caliber with a range in excess of 16,000 yards; the carriage
should provide for wide traverse and must have sufficient mobility
to accompany the army in the field. It will probably be necessary to
transport this howitzer in more than one load, and the maximum weight
of any load should not exceed 12 tons. The average time necessary for
occupying a position should not exceed six hours under actual field
conditions.

=Heavy Field Howitzer. Ideal.= A caliber of about 8” on a carriage
permitting a vertical arc of fire of from 0 to plus 65 degrees; and
a horizontal arc of fire of 360 degrees. The maximum range should be
18,000 yards.

=Heavy Field Howitzer. Practical.= Use at present 8” material of
British design which is on hand.

=Railway Artillery.= The war has demonstrated the necessity for long
range and powerful guns for distant interdiction and harassing work
and for super-heavy howitzers for the destruction of semi-permanent
fortifications. Artillery of these types can best be mounted on railway
carriages and this type of mount offers no serious disadvantages since
these guns will not be used except with large forces which require
extensive railroad systems for their supply. This does not apply to
guns of the type used to bombard Paris; such guns have no military
value and their construction is not justifiable.


ANTI-AIRCRAFT GUNS.

=Light Gun. Ideal.= Caliber about 3” with initial velocity of at
least 2,600 f. s.; semi-automatic breechblock, mounted on carriage,
permitting 80 degrees elevation and 360 degrees traverse; projectiles
weighing not less than 15 pounds, of one type high explosive shell with
maximum ballistic qualities and as large explosive charge as possible;
fixed ammunition; smokeless, flashless powder, mechanical fuse. In
this type every effort must be made to increase the rate of fire and
decrease time of flight; this latter is limited only by considerations
of a reasonable accuracy life for the gun.

=Light Gun. Practical.= Arm units with present 3” anti-aircraft
equipment. Continue experiments leading to the development of the ideal.

=Transport. Ideal.= Caterpillar mount or caterpillar trailer mount
drawn by caterpillar tractor, each unit to permit a sustained speed of
12 miles per hour.




CHAPTER V

THE 3-INCH FIELD GUN.


THE GUN.

The =Gun= is known officially as the _3-inch Field Gun, Model 1905_.
It is a built-up construction of nickel-steel and consists of a tube
with a rifled bore, 3 inches in diameter, upon which are shrunk the
jacket, locking hoop and front clip hoop. The jacket reinforces the
rear half of the tube. The locking hoop serves to secure the jacket
from any longitudinal movement to the rear. On the under side of the
gun, extending the entire length of the jacket, locking hoop, and front
clip, are formed two recoil guides or clips which fit over and secure
the gun to the guide rails of the cradle. When the gun is fired, it
slides along the guide rails. The dust guard covers the part of the
guide rails between the locking hoop and the front clip. The rifling
of the bore is right-hand twist and starts with 0 turns at the breech
increasing to 1 turn in 25 calibers at 10 inches from the muzzle, then
uniform to the muzzle.


Weights and Dimensions.

  Weight of gun                                    788 lbs.
  Calibre                                          3 inches
  Length                                       about 7 feet
  Number of lands and grooves                            24
  Muzzle velocity                             1700 ft. sec.
  Maximum pressure per sq. in.                  33,000 lbs.
  Limit of depression                  (90 mils.) 5 degrees
  Maximum elevation                  (265 mils.) 15 degrees
  Maximum range, trail sunk, about         8,500 yds. (5 M)
  Range at 15° elevation (265 mils)    6,000 yds. (3½ M)

[Illustration: _3 Inch Field Gun, Models of 1904 & 1905._

_Breech Mechanism Assembled._]

Nomenclature of parts of Gun:—

  Jacket.
  Locking hoop.
  Tube.
  Bore.
  Rifling.
  Lands.
  Grooves
  Breech recess.
  Front clip.
  Muzzle.
  Dust guard.
  Recoil guides or clips.
  Chamber.
  Recoil lug.
  Line sight (front and rear).
  Handy oilers.


THE BREECH MECHANISM.

The =breechblock= is of the interrupted-screw type, and is provided
with four threaded and four slotted sectors. The front end of the axial
recess in the block is closed by a bushing. Four ventholes lead from
a cavity in the bushing and permit the escape of gas to the rear in
case of a ruptured primer. On the rear face of the breechblock are cut
gear teeth, in which the gear teeth of the operating lever bevelgear
mesh. The breechblock is concentrically mounted on a hub on the block
carrier, in which the firing-lock case is fitted. Its position in the
breech of the gun with reference to the axis of the bore is eccentric.

The breechblock is closed or locked by a continuous movement of the
operating lever. When the block is swung to the closed position the
front face of the block latch comes in contact with the rear face of
the breech of the gun, thus forcing the latch out of the notch in the
breechblock and back into a recess in the carrier. By continuing the
motion of closing the mechanism, the breechblock is then rotated on
the hub of the carrier and its threads engage with corresponding ones
in the gun. When the breechblock is in the closed position, a lug on
the firing-lock case serves to lock the carrier to the breechblock and
prevents displacement due to a blowback.

=The firing mechanism= belongs to that type known as a continuous-pull
mechanism; that is, no cocking of the firing-pin is required.

=The firing-lock= case is eccentrically fitted in the hub of the block
carrier, in such a position that the axis of the firing-pin is always
in line with the bore of the gun. The vent bushing in the front end of
the breech block through which the firing pin passes when in the fired
position, is fitted eccentrically with reference to the breechblock.
This eccentric arrangement of the breechblock, masks the point of the
firing-pin and prevents any possible contact between the pin and the
primer in the cartridge case when the block is unlocked. The block will
be practically fully locked before any contact between the firing-pin
and primer can take place.

Nomenclature of important parts of Breech & Firing Mechanism.

  Mod. 1905:—

  _Name of Part_                                         _Where located_
  Breech Block                                          On block carrier
  Vent Bushing                                        Front end of block
  Block Carrier                         Hinged to jacket; supports block
  Block Stop                          Screwed into front face of carrier
  Hinge Pin                                     Hinges carrier to jacket
  Hinge Pin Catch                                           In hinge pin
  Extractor                                             In breech recess
  Extractor Lever                                   Mounted on hinge pin
  Operating Lever                               Pivoted on block carrier
  Lever Pivot                              Pivots lever on block carrier
  Lever Latch                                         In operating lever
  Lever Latch Spring                      In operating lever, lower part
  Lever Latch Pivot                       In operating lever, lower part
  Block Latch                                       In recess in carrier
  Block Latch Spring                                   Around latch bolt
  Firing Lock Case                           In hub of the block carrier
  Locking Bolt Nut and Pin     On firing lock case, rear face of carrier
  Firing Pin                    In axle hole, center of firing lock case
  Firing Pin Spring                                    Around firing pin
  Firing Spring Sleeve                          Around firing pin spring
  Sear                                       In slot in firing lock case
  Trigger Fork                                 Rear end firing lock case
  Trigger Shaft                             On rear end firing lock case
  Trigger Shaft Detent                                  On trigger shaft
  Firing Pallet                                          On pallet shank
  Pallet Shank                                      On recoil lug of gun
  Firing Handle                                   On firing handle shaft
  Firing Handle Bracket                 Attached to right side of cradle
  Firing Handle Shaft         Assembled in bracket, right side of cradle
  Trip Latch                              Attached to trip latch plunger
  Trip Latch Plunger                          Assembled to firing handle
  Adjusting Screw                     Assembled to firing handle bracket
  Check Nut                                 Assembled in adjusting screw

[Illustration: _3 Inch Gun Carriage, Model of 1902._

_Plan_]


THE GUN CARRIAGE.

=The gun carriage= for the 3-inch gun Model 1905 is of the type known
as the long-recoil, in which the gun is permitted a sufficient length
of recoil (about 45 inches) upon the carriage to render the latter
stationary under firing stresses. The gun is mounted upon a cradle
which forms a housing for the recoil controlling parts. The cradle
rests upon the rocker and has a small traversing motion of 70 mils on
each side of the axis of the carriage. The rocker is journaled upon the
axle and its rear end is supported by the elevating mechanism, which is
seated in the trail.

The principal parts of the carriage are the wheels, axle, trail
and elevating mechanism forming the lower carriage, the cradle and
recoil-controlling parts constituting the upper carriage, and the
rocker and traversing mechanism intermediate between the two. In
addition there are provided shields, ammunition carriers, the road
brake, and the axle seats.

=The Wheels and the Axle.= The wheels are a modified form of the
Archibald pattern, 56 inches in diameter, with 3-inch tires. The axle
is hollow and forged from a single piece of steel. The wheels are held
on by the wheel fastenings.

=Trail.=—The trail consists of two steel flasks of channel section with
the flanges turned inward, tied together by transoms and plates to
form the sight and the tool boxes. Attached to the trail are the trail
spade, float trail handspike, trail handles and the lunette.

=Elevating Gear.=—The elevating gear is of double-screw type and
consists of an inner and outer elevating screw, an elevating-gear
bracket, an elevating bevel gear, two elevating bevel pinions, and two
elevating crank shafts. The inner elevating screw is a steel screw,
threaded with a right-hand thread. It is attached at its upper end by
the elevating pin to the rear end of the rocker. The outer elevating
screw is of bronze and is threaded on the exterior with a right-hand
thread to take the inner elevating screw. On the exterior are also cut
two longitudinal keyways, in which the keys of the bevel gear work.

=Traversing Mechanism.=—The traversing mechanism consists of a shaft,
called the traversing shaft, mounted in bearings in the traversing-gear
case, and a traversing nut moving longitudinally on the shaft, but
restrained from turning with it by its bearings in the gear case. A
cylindrical lug on top of the nut fits in a hole in a bronze traversing
link, the right end of which is pivoted by the traversing-link pivot
to the traversing lug on the underside of the cradle. This pivot is
secured to the cradle-traversing lug by a nut and split pin. The left
bearing of the traversing shaft is split for the purpose of assembling
and rests between two collars on the shaft. The bearing, with the shaft
in place, is slipped into its seat in the gear case, where it is held
in position by two pins.

[Illustration: _TRAVERSING GEAR, VERTICAL SECTION_]

[Illustration: _Elevating Gear_ _Half Elevation and Half Section_]

=The Cradle Complete.=—The _cradle_ supports the gun, guides it in
recoil, and forms a housing for the recoil-controlling parts; it
consists of a flange steel body with the upper edges flanged outward.
The flanges are bronze lined, engage the clips on the gun, forming the
guide rails for the gun on recoil. Riveted to the bottom of the cradle
are four steel forgings, the pintle, traversing lug, rear clip, and
elevating and traversing lock lug. The pintle fits the pintle socket
in the rocker and forms a bearing upon which the cradle is traversed.
The traversing lug has been heretofore mentioned as affording a point
of attachment for the traversing-link pivot. The cradle rear clip, in
addition to embracing the rear end of the rocker, has a broad bearing
on the latter directly over the point of attachment of the elevating
screw.

To relieve the pointing mechanism from all strains in travelling, an
_elevating and traversing lock_ is provided, by which the cradle may be
securely locked to the trail.

The _recoil-controlling_ parts contained inside the cradle are the
_cylinder_, the _piston rod_, the _counter-recoil buffer_, the
_counter-recoil springs_ and the _spring support_.

To the rear end of the cradle is riveted a steel cradle head, rear,
through which the cylinder moves in recoil and projects for attachment
to the recoil lug on the gun by means of the cylinder end stud and nut.
The front end of the cradle is closed by the cradle head, front, and
the retaining ring.

[Illustration: _Recoil Controlling Mechanism_]

The =cylinder= lies inside the cradle and is surrounded by the
counter-recoil springs. Its rear end is closed and has a projection on
the inside to which is screwed the counter-recoil buffer, a tapered
bronze rod which fits with small clearance into a bore at the rear end
of the piston-rod. The front end of the cylinder is closed by a bronze
oiltight gland, through which the piston-rod slides. The cylinder
is filled with a neutral oil called hydroline. The interior of the
cylinder is cylindrical. Three longitudinal ribs or throttling bars of
uniform width but varying height extend along the interior from the
rear end to within 19 inches from the front end. Three notches are
cut in the piston head, forming ports for the passage of the liquid
from one side of the piston to the other. The height of the throttling
bars is calculated so that the resistance which the liquid offers, plus
the resistance of the springs, is constant and such that the recoil
will be checked at the desired point. During recoil the front end of
the cylinder is supported by the spring support.

The _piston rod_ is of steel, and is provided with a bronze piston
head, screwed against a shoulder at the rear end. The head has three
notches cut in its perimeter, which fit over the throttling-bar
projections on the cylinder wall. The rear end of the piston is bored
out to take the _counter-recoil buffer_. In counter recoil the oil in
this bore can escape only by a small clearance. In this way the return
of the gun into battery is so eased and regulated that very little
shock and consequent derangement of the aim of the piece occur. The
front end of the piston-rod is attached to the cradle head, front, by
means of the piston-rod nut.

The _counter-recoil springs_ (three in number each 36 inches long)
are helical, being made from a rectangular steel bar coiled on edge.
They are assembled in the cradle, end to end around the cylinder and
bear in front against the spring support and in the rear against the
cradle head, rear. They are assembled under an initial compression
of approximately 750 lbs. which is sufficient to return the gun into
battery at the maximum elevation. In place of the single counter-recoil
springs a set of three inner and three outer counter-recoil springs is
also being issued.

The _spring support_ forms a support for the front end of the cylinder
and a bearing for the front end of the spring column. It has guide lugs
which fit into and glide along guide rails inside the cradle during
recoil. The spring support is held in place by the retaining ring.


Action of the Mechanism.

The action of the recoil mechanism when the gun is fired is as
follows:—The gun moves to the rear 45 inches on the cradle, carrying
with it the cylinder and compressing the recoil springs. The piston
rod being attached to a fixed part of the carriage in front, (the
cradle-head) does not move. Therefore, since the cylinder moves to
the rear, the oil in it must pass from one side of the piston head to
the other. The energy of recoil of the gun is therefore absorbed by
the resistance which the oil offers when being forced through small
openings between the notches in the piston head and the throttling bars
along the inside of the cylinder and also by the resistance of the
counter-recoil springs to additional compression. The energy stored up
by the springs during this compression, returns the gun and cylinder
to the firing or original position. This return movement is eased and
regulated by the counter-recoil buffer. The piston rod pull and the
spring resistance are transmitted to the carriage, but owing to the
latter’s weight and the resistance opposed to the trail spade by its
engagement in the ground the carriage remains stationary.


Weights and Dimensions.

  Weight of gun and carriage complete      2,520 lbs.
  Width of track                            60 inches
  Length of recoil on carriage              45 inches
  Amount of traverse of gun on carriage      140 mils

Nomenclature of important parts of the Gun Carriage:—

  Axle
  Trail, consisting of—
    Flasks (right and left)
    Tool box
    Elevating gear transom
    Rear sight box
  Spade
  Spade Edge
  Float
  Handspike fulcrum
  Cradle, head, rear
  Gun slides or Guide Rails
  Cradle Pintle
  Traversing lug
  Rear clip
  Lug for elevating and traversing lock
  Bracket seat, firing handle
  Quadrant fastening
  Rear-sight bracket support
  Front-sight bracket support
  Spring-support guides
  Retaining ring, with hasp and fastening
  Cradle head, front
  Shoulder guard
  Cradle brush
  Recoil-indicator throw
  Recoil indicator
  Cylinder head
  Cylinder with cylinder end screwed in
  Cylinder end stud and nut
  Counter-recoil buffer
  Rings, packing
  Gland
  Piston rod, with plug, screwed in
  Piston
  Piston-rod nut
  Filling plug with gasket
  Drain plug
  Spring support
  Counter-recoil springs
  Rocker
  Cradle Pintle socket
  Elevating and traversing lock
  Traversing mechanism, consisting of—
  Traversing-gear case
  Traversing plate
  Handwheel with handle and spindle
  Traversing shaft
    Traversing-shaft bearing in two parts
    Traversing link with bushing
    Traversing-link pivot with nut
    Azimuth pointer and scale
  Elevating mechanism, consisting of—
    Elevating pin
    Inner elevating screw
    Outer elevating screw
    Wheels guards
    Trail handles
    Trail seats
    Trail-seat supports
    Sponge-staff socket
    Name plate
    Handspike
    Lunette
  Cradle, consisting of—
    Cradle body
    Elevating bevel gear
    Elevating bevel pinions
    Elevating crank shafts, with handles
    Elevating screw cover
  Axle seats, include—
    Seat arms
    Seat-arm guards
    Foot rests
    Tie rods
    Shield braces
  Apron shield
  Apron latches
  Main shield, consisting of—
    Main shield
    Hood
    Shutter, open-sight port
    Shutter, panoramic-sight port
  Top shield, consisting of—
    Top shield
    Top shield fastenings
  Road brake, includes—
    Brake beams
    Brake shoes
    Springs with covers
    Brake rods
    Brake lever
    Brake shaft
    Brake segment with two segment racks
  Ammunition carriers
  Range quadrant case
  Panoramic sight case
  Front sight
  Rear sight, consisting of—
    Rear-sight bracket with shank socket
    Rear-sight shank
  Panoramic sight
  Range quadrant
  Wheels, consisting of—
    Felloe, segments
    Spokes
    Tires
    Hub boxes
    Hub liners
    Hub-latch plungers
    Oil Valve
    Carriage bolts and nuts
    Hub bands
    Hub caps
    Wheel fastenings
    Plugs


THE 3-INCH GUN (CAISSON) LIMBER.

The =limber= is of metal throughout excepting the spokes and felloes of
the wheels. The principal parts are the wheels, axle, pintle, frame,
ammunition chest, pole, doubletree, singletrees, and neck yoke.

The wheels and wheel fastenings are the same as, and interchangeable
with those used on the carriage. Seats for three cannoneers are
provided by a perforated metal bucket-holder on top of the chest. The
paulin issued to each limber serves as a seat cushion and is held in
place by paulin straps. Grip straps are also provided for use by the
cannoneers when the carriage is moving at rapid gaits. On the sides and
front of, and under the ammunition chest, suitable straps, brackets
and connections are provided for securing all tools and accessories.
With each limber are issued three tubular oil cans, each in the form of
a cartridge and with a capacity of two-thirds of a gallon. These are
intended to hold hydroline, lubricating and coal oil and are carried in
the central row of cartridge holes in the ammunition chest.

[Illustration: 3 INCH GUN CAISSON LIMBER, MODEL OF 1916

SIDE AND REAR VIEWS.]


Weights and Dimensions.

  Weight of limber, completely equipped and loaded   1740 lbs.
  Weight of gun, carriage and limber, completely
      equipped and loaded                            4260 lbs.
  Number of rounds carried                                  36

Nomenclature of important parts of limber:—

  Pole, complete, consisting of—
    Pole body
    Neck-yoke counter stop
    Neck-yoke stop
    Neck-yoke chafing plate
    Butt reinforce
  Doubletree
  Doubletree rods
  Name plate
  Limber prop
  Foot rest
  Tie-rods
  Pintle with bearing, consisting of—
    Pintle
    Pintle latch
    Pintle latch spring
  Wheels and wheel fastenings
  Axle
  Middle rail
  Side rails
  Ammunition chest, consisting of—
    Hand rail
    Door chains
    Shot bolts
    Bucket holder
    Chest rails
    Chest-rail connections
    Body
    Door
    Cartridge holes
    Diaphragms
    Lantern brackets
    Grip-straps
    Paulin straps
    Various tool brackets
    Various tools
    Paulins
    Picket ropes
    Lanterns
    Canvas buckets


THE CAISSON

The Caisson is made of metal throughout with the exception of the
spokes and felloes of the wheels. The principal parts are the wheels,
axle, pintle, lunette, apron shield, fuze setter bracket, frame, road
brake, and ammunition chest.

[Illustration: _Caisson, Plan_]

The wheels and wheel fastenings are interchangeable with those of
the gun carriage and the limber. The caisson road brake is modeled
after that of the gun carriage, all parts as far as possible being
interchangeable. The frame upon which the ammunition chest rests,
is diamond shaped, and consists principally of two steel side rails
riveted to lugs on the axle, meeting in front to form the lunette for
attachment to the limber, and in rear to form a pintle for attachment
of another caisson in case it is desired to tow several caissons by
one team and limber, as for instance in the ammunition train. In other
respects the construction is similar to that of the limber excepting
that the ammunition chest is much larger and has a capacity of 70
rounds. The front of the chest and the chest door are made of armor
plate. A bracket for the fuse setter is also provided. An apron shield,
similar to the one on the gun carriage is hinged under the axle, giving
the cannoneers at the caisson full protection. A spare-pole body can be
carried under the caisson frame, large end of pole to the front. On the
sides and front of, and under the ammunition chest, suitable straps,
brackets and connections are provided for securing all tools and
accessories. To lock the caissons and limbers, a padlock is provided.
These locks are interchangeable and can be unlocked by the same key.
This key is marked “Ammunition.”


Weights and Dimensions.

  Weight of caisson only, completely equipped and
      loaded                                              2820 lbs.
  Weight of caisson and limber, both completely
      equipped and loaded with 106 rounds                 4560 lbs.
  Number of rounds of ammunition carried in caisson only         70

Nomenclature of important parts of Caisson:—

  Wheels
  Wheel fastenings, complete
    Axle
    Middle-rails
  Side rails
  Pintle with bearing, consisting of—
    Pintle
    Pintle latch
    Pintle-latch spring
  Name plate
  Channel supports
  Frame handles
  Lunette, with nut
  Caisson prop, with chains
  Road brake, consisting of—
    Brake-beams
    Brake shoes
    Brake rods
    Brake-rod springs and covers
    Brake shaft, with two keys
    Brake segment
    Segment rack
    Brake lever
  Spare-pole fastening
  Ammunition chest, consisting of—
    Diaphragms
    Grip-straps
    Paulin-straps
    Chest rails
    Foot rest
    Handrails
    Door props
    Door handles
    Hand rails
  Supports and Brackets for attaching various tools and accessories
  Apron
  Apron latches
  Fuze-setter bracket
  Fuze-setter latch
  Fuze setter
  Paulin
  Picket ropes
  Various tools and accessories
  Spare pole


To Dismount and to Assemble Parts of the Gun and Carriage.

=To dismantle and to assemble the breech mechanism.=—Grasp the
operating lever and open the breech; when the block is open, force the
block latch out of its seat in the block by gently pressing it into
its seat in the carrier. Take hold of the block and revolve it to the
left until it stops; then pull it to the rear, taking care not to drop
it. The block latch can now be readily removed. After the firing-lock
case has been removed the operating lever can be removed by forcing
its pivot up from beneath by a gentle pressure from the palm of the
hand. The lever latch can be removed by pressing in on the latch at
a point near its lower end opposite its pivot; a hole in the latch
is cut eccentric with reference to the pivot and a shoulder on the
pivot prevents their displacement until the latch is forced in and the
hole is concentric with the pivot. When this occurs, the pivot can be
readily pulled out and the latch removed. To remove the block carrier
force the hinge pin up by hand until it can be caught by the head,
and by swinging the carrier back and forth, if the pin sticks, it can
readily be removed, taking care not to drop the extractor lever. The
extractor can now be removed from the gun.

=To dismantle and to assemble the firing-lock case and mechanism.=—Take
hold of the milled headed locking bolt situated at the lower end of
the firing-lock case, pull it to the rear; at the same time revolve
the firing-lock case upward about 45° and pull it gently to the rear.
This will remove the case with the firing mechanism complete from
the gun. Press the trigger-shaft detent until it disengages from the
notch in the firing-lock case. This will allow the trigger shaft with
its detent, to be withdrawn. Then gently press on the front end of
the firing pin, forcing it back into the casing. This will allow the
trigger fork to fall out. Then, with one finger placed on the front
end of the sear, force it outward; at the same time grasp the front
end of the firing pin, which is roughened for the purpose. Give it a
sharp pull. This will remove the firing-pin spring and sleeve from the
casing. Then place the front end of the firing pin against a block
of wood, bear down on the firing-spring sleeve until the spring is
compressed sufficiently to disengage the slot in the rear end of the
sleeve from the small lug on the rear end of the firing pin; slightly
turn the sleeve, and then the sleeve can be separated from the spring
and pin. By an unscrewing motion the spring can be removed from the
pin. The sear can be removed by gently pressing it in toward the center
of the casing.

To assemble, reverse these operations, taking care before driving
too hard on the end of the trigger shaft that the square hole in the
trigger fork is in position to receive the tapered end of the trigger
shaft. No tools are required for assembling or dismantling this
mechanism.

=To remove the recoil indicator.=—The ends of the clips of the
recoil-indicator guide are bent down to form stops to hold the
indicator in place. To remove the indicator, these parts are opened up
sufficiently to permit sliding the indicator out of the guide. When the
indicator is assembled, these clips should always be closed down to
prevent its loss.

=To dismount the gun.=—Elevate the muzzle slightly. Remove the recoil
indicator throw, unscrew the cylinder-end stud nut, and shove the gun
to the rear until the clips are free from the guides. As the gun slides
off the cradle, it must be properly supported. For this purpose, from 6
to 8 men working in pairs with lifting bars are required.

=To mount the gun.=—Depress the muzzle slightly. Shove the piece from
the rear over the cradle guides with the clips engaging the guides.
Assemble the cylinder-end stud nut, taking care that the locking stud
on the recoil lug enters one of the recesses provided for it in the end
of the cylinder. Assemble the recoil indicator throw. The dust guard
should be assembled with the gun.

In moving the gun on or off of the cradle particular care must be taken
to support the breech end so that the gun clips remain in line with
the gun slides. The firing shaft is also quite liable to injury during
this operation, and care should be taken to prevent its being struck by
the nozzle of the gun or by implements in the hands of the cannoneers.
The cradle should be placed at the desired elevation and azimuth
before beginning either of these operations and not changed during
its progress, since the working of either the elevating or traversing
mechanisms when the gun is only part way in battery brings an excessive
and unnecessary strain and wear upon those parts.

=To dismount the cylinder.=—Bring the gun to approximately zero degrees
elevation; unscrew the cylinder-end stud nut and the piston-rod nut;
remove the cradle head, front. The cylinder is now free and may be
pulled out to the front.

=To assemble the cylinder in the cradle.=—The counter-recoil springs
and the retaining ring being in assembled position, shove the cylinder
(turned so that the drain plug in cylinder head comes on top) into its
seat from the front, with the projecting stud on the recoil lug of
the gun entering one of the recesses provided for it in the cylinder
end; assemble the cradle head; screw in place the piston-rod nut and
cylinder-end stud nut.

_Be sure that the projecting stud on the gun enters one of the holes
for it in the cylinder end before screwing the cylinder-end stud nut up
all the way._

=To assemble the parts of cylinder after cleaning.=—The parts should
be reassembled immediately after cleaning and inspection, and the
cylinder filled with hydroline oil issued for that purpose. The piston
should be moved back and forth in the cylinder by hand to make sure
that all parts are correctly assembled and are without interference.
The cylinder should then be assembled in the cradle and the gun pulled
from battery by hand and permitted to counter recoil rapidly to insure
that all parts are in proper position for firing. _This should never be
done, however, unless the cylinder is known to be filled with oil._ In
reassembling the parts the condition of the vulcanized-fibre washers
between cylinder head and cylinder, and between cylinder-end stud
and cylinder end should be noted; they should be replaced whenever
necessary to prevent leakage. In removing and inserting the piston rod
care should be taken to keep it central in the cylinder, so as not to
bind, burr, or spring any parts. _The dismounting and reassembling
of the parts of the cylinder should in every case be supervised by a
commissioned officer._ Before firing an inspection should be made to
ascertain that the different parts, especially the piston rod and the
cylinder-end stud nuts, are correctly assembled.

=To pack the stuffing box.=—The stuffing box is packed with five rings
of Garlock’s hydraulic waterproof packing, 0.25 inch square. The
packing is issued cut into rings of such size that the ends meet around
the piston rod. The latter being assembled, each ring, placed so as
to break joints with the preceding one, is forced in succession into
its seat by a packing tool of copper or hard wood, one end of which is
shaped like a carpenter’s gouge and the other end forms a handle strong
enough to stand light taps from a hammer. Such a tool may be readily
improvised by one of the battery mechanics. After the five rings are
firmly seated in the box, screw the gland down on the packing.

In assembling the glands be sure that _at least four_ of its threads
are engaged with the threads of the cylinder head; otherwise the
threads of the gland may be stripped in firing. With new packing it may
be found difficult to insert more than four rings and secure sufficient
engagement of the gland. In such a case the box should be packed with
four rings and the piece fired a few rounds, after which the fifth ring
should be inserted.

=Adjustment of the gland.=—The adjustment of the gland will require
the exercise of some judgment. If screwed up too tight, the frictional
resistance of the packing on the piston rod will be increased so much
that the counter-recoil springs may fail to return the gun to battery,
especially at high angles of elevation. _It should be screwed up just
tight enough to prevent the leakage of oil through the stuffing box._
Ordinarily this can be done by hand, but in cases where hand power is
not sufficient the wrench provided for the purpose should be used. When
its proper adjustment is determined, the gland should be lashed with
copper wire to prevent it from screwing up or unscrewing.

=To remove the piston rod.=—Unscrew the gland sufficiently to release
the pressure of the packing upon the rod; unscrew and remove the
cylinder head. The rod may then be withdrawn from the cylinder. In
dismounting and assembling the cylinder head (and also the cylinder-end
stud), the cylinder should be held from turning by a spanner applied
to the head retainer or flange on the front end of the cylinder. _It
should never he clamped in a vise_, as its walls are thin and not
intended to withstand such usage.

=To remove the counter-recoil buffer.=—Remove the cylinder-end stud
screw; unscrew and remove the cylinder-end stud; the counter-recoil
buffer is attached to the latter.

=To dismount the springs.=—Bring the gun to approximately zero degrees
elevation; unscrew the cylinder-end stud nut and the piston-rod nut;
shove the gun about 1 inch from the battery; attach the sleeve end
of the spring compressor to the cylinder-end stud and put sufficient
strain on the compressor to relieve the retaining ring from spring
pressure; then remove retaining ring (and cradle head) by loosening and
swinging aside the retaining-ring bolts; ease off slowly on the spring
compressor until the springs are free.

=To assemble the double counter-recoil springs.=—With the cradle at
maximum elevation and the trail horizontal, place one outer and one
inner spring in the cradle until the front ends are about 2 inches
in; set up a separator against the forward end of these sections and
enter the second outer and inner springs, keeping the separator upheld
between the sections; similarly when the outer end of the second
section is 2 inches inside the cradle set up the second separator;
place the third outer and inner sections on the recoil cylinder. Screw
the spring centering tool onto the cylinder-end stud, the small end
pointing rearward; pass the sleeve end of the spring compressor through
the gun lug and the inner springs and attach it to the cylinder-end
stud. Enter the rear end of the cylinder in the spring at the front
end of the cradle and push the cylinder back until the springs are at
free height, keeping the spring compressor taut. Attach the block and
fall carried in the battery wagon to the spade of the carriage or to
some improvised support and connect it to the spring compressor; put
sufficient strain on the spring compressor to bring the spring column
to its assembled height.

As the spring column approaches its assembled height the spring
support must be turned so that its guide lugs properly enter in the
spring-support guide grooves in the cradle; assemble the retaining
ring, disconnect the spring compressor and the spring centering tool
from the cylinder-end stud; push the gun back into battery and assemble
the cylinder-end stud nut. When the retaining ring is assembled the
nuts for the retaining ring bolts should be screwed up until they just
come into contact with the retaining ring. If these nuts are screwed up
too tight they will deform the retaining ring, with the result that it
becomes difficult to assemble and dismount the cradle head. A wrench is
provided for turning the spring support to its proper position.

=To assemble the single counter recoil spring.=—The same method is
followed except that no separators are used. The spring compressor is
provided with a second eye at its large end which may be used in case
the sleeve end should become broken; in case this end is used, however,
it will be necessary to pass the compressor through the cradle from
front to rear, through the gun lug. For disconnecting the compressor
the method used is identical to that previously described.

_The cylinder-end stud nut should never be removed when the gun is at
an elevation_, and the gun should not be elevated when the cylinder-end
stud nut is not in place. To prevent the cylinder-end stud from
rotating a screw for the cylinder end is provided. _This screw for
the cylinder end must be removed before attempting to unscrew the
cylinder-end stud._

Since the springs are assembled under an initial load of over 750
pounds, a pull of more than 750 pounds must be exerted upon the spring
compressor in assembling them. This can be done by passing a handspike
through the loop at the rear end of the compressor and making use of
the service of the entire gun squad, or the block and tackle may be
used as described above. _To avoid the possibility of injury to the gun
squad in compressing or releasing the springs, all should be required
to keep arms and bodies away from the front of the spring column during
these operations._




CHAPTER VI

FRENCH 75


GUN.


=Weights and Dimensions.=

  Weight                                            1015 lbs.
  Total Length                                (about) 107 in.
  Rifling                                          24 grooves
  Twist—right-hand slope, 7 degrees, 1 turn in 25.6 calibers.


CARRIAGE.


=Weights and Dimensions.=

  Weight complete                                         1642 lbs.
  Weight of gun and carriage complete                     2657 lbs.
  Weight at end of trail, carriage limbered                114 lbs.
  Diameter of wheels                                       52.5 in.
  Length of recoil                                   (about) 45 in.
  Maximum angle of elevation                 (338 mils.) 19 degrees
  Maximum angle of depression                (178 mils.) 10 degrees
  Amount of traverse of gun on carriage       (106 mils.) 6 degrees

=The gun= is of the built-up type and consists of a forged steel tube
which extends from muzzle to breech. A breech hoop is shrunk over the
rear of the tube and extends beyond it to provide a breech recess. This
recess is threaded with seven threads to take the breechblock. A bronze
jacket encircles the central portion of the tube. Inner and outer
locking hoops screw to and firmly fasten the tube, hoop and jacket
together and prevent them from separating under the stresses of recoil.
A muzzle hoop is screwed on the tube at the end of the muzzle.

[Illustration: _75 M.M. FIELD GUN_

_MODEL OF 1897_ (_FRENCH_)]

[Illustration: 75 M.M. FIELD GUN

MODEL OF 1897

(FRENCH)]

A recoil lug on the under side of the breech hoop forms a point of
attachment between gun and recoil mechanism through the media of a
piston rod and coupling key.

The rear sight is attached to the rear portion of the breech hoop. On
top of the hoop at its rear end are two quadrant seat plugs. The front
sight is fixed on top of the rear end of the jacket. A sweeper plate
which sweeps and lubricates the roller is secured to the front end of
the jacket.

=The breechblock= is the Nordenfeld rotating type, cylindrical with
seven threads which serve to screw it into the rear of the breech. The
breech is opened and closed by rotating the block 120 degrees around
its axis. The block advances during the rotation due to the pitch of
its threads and forces the cartridge case into the bore. The gun cannot
be fired until the block has been completely closed, a condition which
must exist before the striker of the firing mechanism is in line with
the primer cartridge of the projectile.

=The extractor= consists of three parts:

1. Two arms connected by a hollow shaft.

2. A spindle which passes through the shaft and fastens it to the
breech.

3. An extractor tang.

=The action of the extractor= is as follows: When the breech is closed
the arms of the extractor are pressed against the face of the tube by
the rim of the cartridge case which bears against them. The extractor
tang projects into a groove in the inner face of the breechblock known
as the loading groove. This groove is circular and its depth is equal
to the projection of the extractor tang. It terminates in a helical
guide surface called the “ejecting ramp.”

[Illustration: 75 M.M. FIELD GUN

MODEL OF 1897

(FRENCH)]

The first part of the movement of opening the breech serves to move
the grooves in front of the extractor tang. This pressure forces the
extractor tang back into its slot in the breech hoop and as the
extractor tang is firmly seated in the extractor, the arms of the
latter are rotated around the extractor spindle. The arms being brought
to the rear, press against the rim of the cartridge case, which is
thereby started and ejected.

Inversely (the breech being open) when a cartridge case is smartly
inserted in the chamber the rim carries the arms of the extractor
forward. The extractor tang is thereby forced against the beveled
surface of the ejecting ramp and automatically starts the closing
movement of the breechblock.

A safety catch is provided to keep the breech locked between the time
that the breech is closed and the shot is fired.

=The firing mechanism= consists of a striker or firing pin seated in
the breechblock, a firing hammer, firing rack, spring and lanyard. By
pulling the lanyard the hammer is drawn back and the rack moves forward
against the compression of the spring due to its being geared to the
hammer. When the lanyard is released, the spring forces the rack back
which in turn causes the hammer to fly forward and strike the primer. A
safety device is provided for locking the hammer while the piece is in
the traveling position.


THE CARRIAGE.

The gun is mounted upon a cradle which encloses the recoil and
counter-recoil mechanisms. The device for elevating the gun through the
angle between the horizontal and the line gun-target (angle of site)
is interposed between the trail and the rocker while the device for
giving the gun elevation for range is placed between the rocker and
the cradle. This arrangement is known as the independent angle of site
or independent line of sight. It has the advantage over the three-inch
type in that it allows the range elevation to be altered without
disturbing the elevation for site.

[Illustration: 75 MM. GUN CARRIAGE, MODEL OF 1897 MI(FRENCH).

_LONGITUDINAL SECTION_]

[Illustration: 75 MM. GUN CARRIAGE

MODEL OF 1897 MI FRENCH

REAR VIEW]

[Illustration: 75 MM. GUN CARRIAGE

MODEL OF 1897 MI(FRENCH)

LEFT SIDE]

[Illustration: 75 MM. GUN CARRIAGE

MODEL OF 1897 MI(FRENCH)

RIGHT SIDE]

[Illustration: 75 MM. GUN CARRIAGE

MODEL OF 1897 MI(FRENCH)

PLAN VIEW]

=The principal parts= of the carriage are: trail, axle, wheels, brakes,
shields, angle of site elevating mechanism, range elevating mechanism,
traversing mechanism, rocker, cradle and sights.

When traveling or resting, the tube rests on the =cradle= which
supports it by means of the jacket. When firing, it recoils on the
cradle by means of the rollers. The jacket has two pairs of rollers,
and the muzzle hoop is provided with a single pair of rollers. On the
upper part of the cradle are the lower slides, on which the jacket
rollers, supporting the tube, roll during the recoil. When the jacket
rollers are about to leave the lower slides, the muzzle rollers come
under the upper slides; the tube is then supported until the end of
the recoil by the muzzle rollers and the more forward of the two pairs
of jacket rollers. This device gives the gun a long recoil upon short
slides. Inclined planes are used in such a manner that when the gun
returns into battery the rollers rise from the lower slides thereby
relieving the slides from the weight of the tube when the tube is in
the traveling position.

The carriage supports the cradle which in turn supports the tube. The
cradle and the tube together are displaced, during the laying for
elevation with respect to the carriage which remains stationary. The
carriage is held steady on the ground by means of the trail spade which
with abatage prevents the carriage from recoiling on the ground.

=Abatage= consists of elevating the wheels on the brake shoes which are
provided with small spades which prevent lateral movement. The brake
shoes are fastened to brake beams attached to a sliding rack beneath
the trail in such a manner that the abatage frame may be placed under
the carriage during travel. In preparing to fire, the frame may be
adjusted to allow the brake shoes to slip from a position in rear of
the carriage wheels to a point directly beneath the wheels.

[Illustration: _75-MM. GUN CARRIAGE, MODEL OF 1897, MI(FRENCH) WHEEL
BRAKE MECHANISM_]

Abatage is accomplished as follows: (1) The brake shoes are dropped
to the ground in rear of the point of contact of the wheels with the
ground; (2) The trail is lifted, turning around the axle, until the
spade is about five feet in the air. Tie rods and a slide working on a
rack beneath the trail move forward in this action; (3) The trail is
then brought down. The rack prevents the slide from moving to the rear
and the carriage turns on the abatage frame until the wheels rest upon
the brake shoes. This gives the gun a three point support, two small
spades under the wheels and a larger one at the end of the trail.

=Laying in direction= is accomplished by traversing the piece on the
axle. The trail spade is fixed and the axle is straight and rigid so
that in the movement of the gun to the right and left on the axle both
wheels must turn—one to the front and one to the rear. The device for
laying for direction is composed of a threaded axle, which is prevented
from rotating by a spur and a sliding nut which is contained in a box
fixed on the left flask of the gun. This nut bears one of the bevel
gears, which is put in motion by the hand wheel. The traverse is three
degrees either side of the center or a total of 6 degrees or about 105
mils.

=Laying for elevation.= To obtain greater accuracy and speed in firing
the 75 has an independent angle of site. A rocker with two trunnions is
interposed between the cradle and the carriage. The rocker trunnions
are seated in the cradle trunnions and support them. This gives the
same rotating axis to both rocker and cradle. This is necessary for
the mechanical addition of the angle of site elevation and for the
range elevation. When the angle of site handwheel is revolved it turns
a pinion, which meshes in the rocker rack and thus causes the rocker
to move in relation to the carriage. This gives the cradle through the
rocker the elevation equal to the difference in elevation between the
target and the gun. It is independent of the angle given to the gun for
the elevation due to range to the target.

[Illustration: 75 MM. GUN CARRIAGE, MODEL OF 1897 MI(FRENCH).

_RANGE ELEVATING MECHANISM_]

The angle given the gun for range is effected through a telescopic
screw. This screw is fastened at one of its extremities in the rocker
and at the other in the cradle. The nut which receives the elevating
screw is seated in an oscillating support which allows it to always
remain perpendicular to the axis of the bore at any elevation.

The angular displacements of the cradle with respect to the rocker
(angle of elevation) are recorded by the elevating system composed of a
graduated arc and a range drum. The lower part of the arc is connected
with the right arm of the rocker. The arc is graduated in meters. When
the range handle is turned the arc does not move, but a brass slide
block connected with the gun and the cradle and bearing an index slides
along the arc. It is thus possible to set the range in meters.

However, the arc graduations are not very legible and it has been
supplanted by a graduated range drum having more legible readings.

The black part of the arc bears a rack which meshes with a pinion,
which in turn rotates around an axle fixed on the cradle. When the
cradle moves, the pinion rotates and carries with it the range drum.

The elevation on level ground varies from a minus 11 degrees to a plus
20 degrees. Greater elevation may be obtained by sinking the spade.

=The Recoil and Counter-recoil mechanisms= are of the Hydro-pneumatic
type. Their accurate description is a secret. The following brief
description will give only a general idea of the working of the
mechanism. The whole apparatus is inside of the cradle through which
are bored two cylinders: an upper cylinder 40 mm diameter, and a lower
cylinder 66 mm diameter. These cylinders may communicate through a
large hole. A piston moves in the upper cylinder, the piston rod, 24 mm
diameter, being fast to the gun.

In the lower cylinder are: (1) The valve carrier pipe screwed in the
rear part of the cylinder supporting =spring valves=; in the inner
walls of the pipe are cut two grooves; the valve carrier pipe is ended
by a circular ring. (2) =The diaphragm= with its hollow rod. (3) =The
loose piston= with its small rod, which may come in contact with the
upper rack of the gauge. The two cylinders are full of liquid, usually
Russian oil. The front part of the upper cylinder in front of the
piston may communicate freely with the air through the Front Plug.
The front part of the lower cylinder is closed by a plug and contains
compressed air at a pressure of 150 kg. per sq. cm.

=Operation.= In recoil the piston of the upper cylinder compresses the
liquid, which has to pass through the spring valves and between the
circular ring and the hollow rod of the diaphragm. The passage of the
liquid through these different openings constitutes the braking effect.
In so moving the liquid opens the valves, which are widely opened at
the beginning of the recoil and gradually close in proportion to the
decrease of the speed of the recoil. At the same time, the air of the
recuperator is compressed by the action of the liquid on the diaphragm.

When the recoil is finished, the compressed air pushes back the
diaphragm. The liquid thus compressed acts on the small cylinder piston
and obliges it to come back into its initial position, bringing with it
the tube.

The liquid in flowing back completely closes the valves and must pass
between the diaphragm rod and the inner wall of the pipe. At beginning
of the return into battery, the space between the rod and the bottom of
the groove is large. This space decreases in proportion to the progress
of the return. The passing of the liquid through this constantly
decreasing space causes the braking which at the end reduces the speed
of the return to nil.


CARE AND PRESERVATION OF FRENCH 75.


Dismountings.

  =Cannoneer Dismountings.=
  A.  Breechblock.
      1.   Safety piece.
      2.   Striker.
      3.   Lanyard.
      4.   Striker hammer.
      5.   Hammer spindle.
      6.   Spring assembling pin.
      7.   Rack springs.
      8.   Rack.
      9.   Latch pin. (Pawl Pin.)
     10.  Latch (Pawl).
     11.  Latch spring. (Pawl spring.)
  B.  Extractor.
      1.   Clow. (Tang.)
      2.   Spindle.
      3.   Arms.
  C.  Level.
  D.  Sight case.
  E.  Wheels.
  F.  Limber pole.
  G.  Fuze setter from caisson.
  H.  Luggage frame from limber.

  =Mechanic Dismountings.=
  A.  Coupling keg.
  B.  Push gun back on slides.
  C.  Safety bolt.
  D.  Friction piece. (Sweeper plate.)
  E.  Wiper. (Guide piece.)
  F.  Front plug.
  G.  Filling hole plug.
  H.  Elevating screw pin.
  I.  Elevating screw.
  J.  Trunnion caps.
  K.  Rocker Trunnion caps. (Half Rings.)

  =Daily Cleaning and Lubricating.=
            (By cannoneers.)
      1. Clean sight support and socket.
      2. Lubricate oil holes 20, 21, 22, 23, 24.
      3. Clean base of sight column.
      4. Clean levels.
      5. Lubricate range mechanism. (Holes Nos. 1 and 2.)
      6. Clean and oil rocker trunnion caps.
      7. Oil holes 7 and 8.
      8. Clean and grease exposed parts of axle.
      9. Dismount and clean breech and all its parts.
     10. Clean and grease the bore if the gun has been fired.
     11. Clean and grease the slides if the gun has been fired.
     12. Grease the wheels if the gun has been on the road.
     13. Clean fuze setter.
     14. The life of a gun depends on “Daily Care.”

  =Forbidden Practices.=
      1. =Readjustment of French Sights=.
      2. =Fitting with files=.
      3. =Forging and Riveting=.
      4. =Unauthorized Dismountings=.


Care of Recoil Mechanism.

(_Chief Mechanic Only_)

=Caution.=—Never remove piston rod nut, as piston is under pressure and
would pull piston rod into cylinder.

The recoil apparatus proper cannot be dismounted.

If properly taken care of the recoil mechanism will not go wrong for
years; but if neglected, its destruction is only a matter of very
little firing.

The position of the gauge finger is the index as to whether or not the
recoil is being properly absorbed.

The joints are not absolutely tight, the slight leakage which takes
place during fire or even when gun is at rest is not important.

In normal firing conditions the recoil apparatus contains a slightly
greater quantity of oil than absolutely necessary; this quantity is
called the “reserve.” When the reserve is exhausted any loss is liable
to reduce the quantity strictly necessary. The loss may prevent the gun
from fully returning to battery when firing.

The amount of reserve is indicated by the position of the gauge.

No reserve: The gauge finger is down deep in its recess.

Full reserve: The end of the gauge finger is level with the gauge index.

Excess reserve: The gauge finger projects beyond the index.

_No firing should be done with an excess reserve._

_The gauge finger should be between the index and ⅛ inch below the
index._

It is the duty of the Chief Mechanic to see that the gauge finger is in
the proper position before firing.

It is the duty of the Executive and the Chief of Section to see that
the gauge finger is in the proper position during fire; if it moves
from this position the Chief Mechanic will be called to make the proper
adjustments.

When the gauge finger has been brought to the proper position there are
only two conditions which call for tampering with recoil apparatus.

1. The gun goes into battery too slowly, or has to be pushed in.

In this case the gauge finger will usually be found too deep in its
seat, and the pump will have to be used. If the gauge is in the proper
position look at the slides. Either they will be found dirty or bits of
the wiper may be nicked off. In the latter case the gun can be fired
without the wiper.

2. The gun jumps badly. In this case the gauge finger will generally be
found beyond the index. When this is the case the oil extractor must be
used until the gauge finger is in the proper position.

If after cleaning slides, putting gun in abatage and adjusting gauge
finger, the gun still jumps badly—complete draining of the reserve and
refilling will frequently remedy the trouble.




CHAPTER VII.

75-MM. FIELD GUN MODEL 1916.

THE GUN.

  Weights and Dimensions.

  Weight                      Kg   339.74   pounds  749.
  Caliber                     mm    75.     inches    2.953
  Total length                mm 2,308.5    inches   90.9
  Length of bore              mm 2,134.     inches   84.
  Length of rifled portion of
    bore                      mm 1,847.     inches   72.72
    Number of grooves                                24
    Width of grooves          mm     7.30   inches     .2874
    Depth of grooves          mm      .501  inches     .02
    Width of lands            mm     2.52   inches     .0992

Twist, right hand, zero turns from origin to a point 2.89 inches from
origin. Increasing from one turn in 119 calibers at a point 2.89 inches
from origin to one turn in 25.4 calibers at a point 9.72 inches from
muzzle. Uniform from a point 9.72 inches from muzzle to the muzzle.


Description of the 75-MM Field Gun.

=The gun= is built up of alloy-steel forgings, _consisting of a tube,
jacket, breech hoop, and clip_. All of the parts are assembled with a
shrinkage.

_The tube_ extends from the muzzle to the rear end of the powder
chamber and two recesses are cut in its rear face to form seats for the
lips on the extractors.

_The jacket_ is assembled over the muzzle end of the tube. The jacket
carries two flanges on its lower side, which form guides for the gun
in the cradle of the carriage, and a lug on top near the forward end
which contains a T slot, which holds the recoil cylinder in place. The
rear end of the jacket is threaded on the outside to receive the breech
hoop.

_The breech hoop_ is threaded at its forward end and screws on to the
rear of the jacket. The breech ring carries a recoil lug at the top for
the attachment of the hydraulic recoil cylinder, and another lug at the
bottom for attachment of the two spring piston rods. The rear part of
the breech hoop is cut away to form the breech recess.

_The clip_ is a short hoop shrunk on the tube near the muzzle. It
carries two lugs on its under side which form guides for the gun in the
carriage.

The rear ends of the guides on the jacket are extended to the face
of the recoil lugs by short extensions riveted in place to prevent
entrance of dust between surfaces of the guides and their bearing
surfaces on the cradle. For the same purpose the forward ends of the
guides on the jacket are connected by steel-plate dust guards with the
rear ends of the guides on the clip.


Description of the Breech Mechanism.

The mechanism is known as the =drop-block type=, and is semi-automatic
in design in that the block closes automatically when a round of
ammunition is inserted. A rectangular hole extending through the
rectangular section of the breech hoop forms seat for the sliding
block. The upper part of the breech hoop in rear of this slot is cut
away, leaving a U-shaped opening which permits the passage of the
cartridge case.

[Illustration: 75-M.M. FIELD GUN BARREL]

[Illustration: _75-M.M. FIELD GUN MODEL OF 1916 MIII BREECH MECHANISM._]

[Illustration: 75-MM. FIELD GUN MODEL OF 1916 M III BREECH MECHANISM]

Recesses cut in both the side faces of the breech recess form seats
for trunnions for the two extractors. Holes bored into these recesses
from the rear face form seats for the extractor plungers, springs and
plugs. The block slides up and down in the breech recess under the
action of the operating arm which is pivoted on the operating
shaft and acts as an oscillating crank in raising and lowering the
block. The operating shaft which rotates the operating arm is actuated
by the operating handle. The operating handle is provided with a
latch to keep it in the closed position and is connected by a chain,
piston, and piston rod to the closing spring, which is carried in the
closing-spring case. The closing spring is under compression and tends
to keep the block closed or to close the block when it is opened.

When the block is opened as far as it will go, it is locked in that
position by the inside trunnions on the extractors. These trunnions are
forced over horizontal shoulders on the block by means of the extractor
plungers and holds the block in the open position. When a cartridge
is pushed smartly into the gun, its rim striking against the lips on
the extractor frees the trunnions from the shoulders on the block and
allows the block to close under the action of the closing spring.

_A continuous-pull firing mechanism_ is carried in the recess bored out
in the center of the block and is operated by the trigger shaft which
projects from the bottom of the block. This mechanism is cocked and
fired by one continuous motion of the trigger shaft so that in case of
a misfire the primer may be struck a second blow by releasing the shaft
and rotating it again. A lanyard may be attached to the projecting end
of the trigger shaft.


CARRIAGE.

=Weights and Dimensions.=

  Weight of carriage, complete, fully equipped, without
      the gun                                            2280 pounds
  Weight of gun and carriage fully equipped              3045 pounds
  Weight of lunette, carriage limbered                    140 pounds
  Diameter of wheels                                       56 inches
  Width of track, center to center of wheels               60 inches
  Length of recoil of gun on carriage, variable recoil   18 to 46
  Height of axis of gun about ground                   42 approx.
  Amount of elevation with elevating handwheel         42 degrees
  Total limits of elevation                  7 to plus 53 degrees
  Maximum traverse either side of center                 400 mils
  Over all width of trails, spread                     130 inches
  Over all length, muzzle of gun to end of lunette     173 inches
  Limits of elevation with angle of site handwheel, minus
      7 degrees depression to 11 degrees elevation.


Description.

_The carriage_ is of the split trail, variable long-recoil type. The
length of recoil is regulated automatically, so that the breech of the
gun will not strike the ground on recoil at an angle of elevation of
less than 47 degrees. At elevations greater than 47° a hole must be dug
for the breech in recoil.

The gun is mounted in slides on a _cradle_ formed by the spring
cylinder. The spring cylinder is suspended by trunnions mounted in
bearings in the top carriage, which is supported by the pintle bearing
to which are attached axle arms bearing in the wheels.

The carriage has an _independent angle of site_ elevating mechanism,
by means of which a maximum depression of seven degrees and an angle
of elevation of 11 degrees may be obtained. The remaining elevation is
obtained through the elevating handwheel.

  =The principal parts of the carriage are:=

  Trail
  Cradle
  Recoil mechanism
  Top carriage
  Pintle bearing
  Equalizing gear
  Shields
  Angle of site mechanism
  Elevating mechanism
  Traversing mechanism
  Axle seat
  Brake mechanism
  Shoulder guards
  Firing mechanism
  Sight, model of 1916
  Wheels.

[Illustration: 75 MM. GUN CARRIAGE MODEL OF 1916.

LEFT ELEVATION.]

[Illustration: 75 MM GUN CARRIAGE. MODEL OF 1916.

RIGHT ELEVATION.]

_The trail_ is made in two halves of box section built of bent and
riveted steel plate. Each half is bolted to a lug on the equalizing
gear, so that it may be rotated horizontally from the junction point of
the trail to the point where the trail hits the wheel.

The trails are locked together in traveling position by means of a
cone-shaped vertical lug on the lunette bracket which fits in a socket
in the trail coupling, and is locked in place by the trail-coupling
latch. Trail-coupling latch has a handle and catch with a vertical
spindle seated in a socket in the lunette bracket. A handle-return
spring is assembled around the spindle and the latch engages a catch
on the trail coupling when trails are fixed in the traveling position.
Latch is opened by moving handle forward.

_Lunette_ consists of a ring for attaching the carriage to the limber
and is bolted through the lunette bracket.

_Floats are_ attached to the bottoms of both trails at their rear
ends, consisting of flanged steel plates for the purpose of increasing
bearing area of the trails on soft ground.

_Spade bearings_ are riveted to rear of the trails and form bearings
for spades in firing position. Spades are driven through the bearings,
and their upward movement relative to the trails is prevented by spade
latch.

_Spade-latch_ bracket consists of a bronze plate with a cylindrical
chamber for a spring and plunger and two bearings for latch-handle pin.
Bracket is riveted to the inside top of trail in front of the spade.
Spade-latch plunger, with a spring assembled around it, is seated in
the chamber and the spade-latch handle is pinned in the bearing. Top
of handle extends through the trail and is roughened for use as a foot
pedal. Lower part of handle engages with the plunger. When the spade
is driven the plunger is forced into a notch in the spade by means of
the spring, and the slope on face of plunger allows a downward movement
of the spade and prevents upward movement. To release spade the foot
pedal on latch handle is pressed down, disengaging plunger from spade,
and the spade is removed.

_Trail handles_ are riveted to outside of both trails for lifting
trails. Name plate is riveted to outside lower left trail. It is
important that the number of carriage on this plate be recorded by the
officer in charge of the unit to which it is assigned and that this
number be used as a reference in all correspondence. Wheel guards,
rear, are plates riveted to the outside lower left of both trails for
the protection of trail bodies against contact with limber wheels on
short turns. Trail guards are bent plates riveted to the top of trail
in front of trail-coupling latch to prevent battering of trails by
sledges used for driving the spades.

_Sponge-staff_ fastenings are riveted to tops of both trails. Sponge
staffs are inserted in upper rings of staff fastenings and the lower
ends are clamped in place. The smallest section of sponge staffs fits
in sponge fastenings.

_Sledge fastenings_ are similar to sponge staff fastenings and are
riveted to the outside of each trail. Wheel guards (front) are plates
riveted to the outside of trails near the front to prevent contact of
trails with wheels when the trails are separated.

_Spare parts_ case is a steel box with a hinged steel cover provided
with a bolt snap and padlock riveted to the outside of front left
trail. This case contains spare parts for emergency use.

_Trail seats_ are made of formed bent plates riveted to the tops of
trails near breech of gun. Oiler support with springs is under the
right-hand trail seat. Oiler rests on this support and is held in place
by springs.

[Illustration: 75-MM. GUN CARRIAGE, MODEL OF 1916.

REAR VIEW.]

[Illustration: 75 MM. GUN CARRIAGE, MODEL OF 1916.

PLAN VIEW.]

_Traveling lock bar_ consists of a forged steel bar pinned to lock bar
bearing on left trail and made to swing across trails in traveling
position and along left trail in firing position. In traveling position
the socket in the middle of the lock bar engages with the traveling
lock stud in the bottom of cradle, and right end of lock bar is held in
lock bar clip on right trail by the latch. To disengage the latch for
firing, the latch handle is lifted and the lock bar swung to fastening
in left trail, where it latches.

_To lock the cradle_, the gun is brought to 0 azimuth and the traveling
lock pointer on right trunnion cap brought to line marked “March.” In
this position the traveling lock socket fits over stud, and the lock is
latched. The latch consists of a lever pinned at one end to the lock
bar with a plunger pinned in center extending through the bar with a
spring around the plunger body to hold the latch in place.

Trail connections are riveted to front end of trail and bolted to
equalizing pinions.

=The cradle= comprises the spring cylinder with attached parts.

The spring cylinder is below and shorter than the gun. It is in the
form of two cylinders joined at the center, with axes in the same
horizontal plane. Above the cylinders are the gun ways, parallel to
the cylinders, bronze lined, and opening toward the center line of
cylinders. Traveling lock stud is bolted through a lug at the rear
and below the cylinders. Firing-shaft bracket is riveted to the left
side and range-scale bracket to the right side of the cylinder at its
rear end. Shoulder guards are pinned in sockets in both firing-shaft
and range scale brackets to prevent contact of the gun during recoil,
with the cannoneers. Trunnions are riveted and keyed to the cylinder
near center. Elevating arc is bolted to lugs on the bottom of cylinder
at trunnions. Piston-rod bracket is riveted to projections on the
cylinder above the gun slides near the front end. Cylinder cover is
pinned to cylinder clips, which are riveted to the front of spring
cylinder. (Note: On some carriages the clips are made integral with the
cylinder.)

[Illustration: 75 MM GUN CARRIAGE, MODEL OF 1916.

LONGITUDINAL AND TRANSVERSE SECTIONS]

=The recoil mechanism= is designed for variable recoil, the length
of which is regulated automatically by the elevation of the gun. The
following table gives lengths at various elevations: (These lengths are
based on theoretical calculations. Actual lengths of recoil between 8’
and 45’ elevation are generally greater.)

               Elevation.                 Length of Recoil.
            -7.0 to plus 8.0 degrees     46 inches.
            -8.0 to plus 16.47 degrees   46 to 28 inches.
  -16.47 to plus 27.20 degrees           28 inches.
           -27.20 to plus 36.7 degrees   28 to 18 inches.
           -36.7 to plus 53 degrees      18 inches.

The breech of the gun on short recoil will strike the ground at the
level with the bottom of the wheels at an elevation of 47 degrees or
over.

_The recoil mechanism_ is of the _hydraulic spring type_, with the
_recoil cylinder_ mounted above the gun and the counter-recoil springs
in the cradle below the gun. The recoil cylinder is held in place
by a slot machined in the gun jacket at the front and rests in the
cylindrical opening in the gun lug above the rear of the gun. It is
held in place by the cylinder retainer, which screws into the rear
cylinder parallel to the center line.

_The recoil valve_ is a cylinder with a collar at the front end and
three lands inside and parallel to the bore. Three rows of holes are
bored at the lands. The recoil valve fits inside the cylinder, resting
on the lands, and is held in place by a collar bearing against the edge
of the counterbore in the cylinder at the front, while the rear end of
the valve bears against the inside rear end of the cylinder.

_The piston_ is screwed and pinned to the piston rod and is of bronze,
slotted to fit lands and grooves in the recoil valve. The piston rod
is hollow for almost the entire length. The front end passes through
the gland in the cylinder head and piston-rod sleeve. The front of the
recoil cylinder is closed by the front cylinder head, which is screwed
in place with a gasket. A bronze gland with four rings of 5/16 inch
Garlock packing prevents leakage around the piston rod.

_The counter-recoil buffer_ consists of a buffer rod screwed into
the buffer nut at the rear end of the recoil cylinder, and extending
through the buffer bushing into the interior of the piston rod. The
buffer head is screwed and pinned into the front end of the buffer rod.
The buffer head is of two diameters and connected by a short cone. The
rear end is the smaller diameter and is threaded inside to screw over
the buffer rod. The coned surface contains slots leading to a hollow
chamber in front. The front end of head is faced and provided with a
central bearing for valve stem. The bearing is supported by webs to
main body of guide. Valve stem has a stop on rear and a valve screwed
to front. Valve is faced to seat on front of the bearing, webs and
circular face of main body of guide.

_The counter-recoil springs_ are assembled around _spring rods_ in
_spring cylinder_. Spring rods fit in gun lug and are fixed in place
by taper keys driven diagonally through lug and rod. The rod is hollow
for entire length, except at the rear, where the outside diameter is
decreased to permit entrance in gun lug. Collars are screwed and pinned
to front ends of rods. _Three coils of inner counter-recoil springs_
are assembled over the spring rod, surrounded by _three coils of outer
springs_. Inner and outer springs are coiled in opposite direction to
prevent nesting, and sets of coils are separated by a bronze separator.
Rear ends of cylinder are bushed for spring rods.

_The operation of recoil mechanism is as follows_:

When the gun is fired it moves back in slides on cradle, carrying with
it spring rods, buffer rod, recoil cylinder, and recoil valve. The
piston, piston rod, and spring cylinder remain stationary, being fixed
to carriage.

[Illustration: 75 MM GUN CARRIAGE, MODEL OF 1916.

LONGITUDINAL SECTION, RECOIL AND COUNTER RECOIL MECHANISM]

The recoil cylinder being full of oil, this oil is forced by the piston
through holes in recoil valve in front of piston up into annular space
between valve and cylinder and into space behind and vacated by the
piston. The hydraulic resistance caused by forcing the oil through
the holes in valve absorbs most of the recoil energy of the gun, and
the remaining energy is taken up by compression of the counter-recoil
springs and friction.

When the gun reaches the end of recoil all of the recoil energy has
been absorbed and the counter-recoil springs acting against spring-rod
piston force the gun back to battery position. The purpose of the
counter-recoil buffer is to overcome the tendency for gun to return
to battery too rapidly, at the same time allowing sufficient speed
of counter recoil to permit maximum rapidity of fire. Buffer action
is necessary, as the strength of springs required to return the gun
to battery at high elevations is greater than is required at lower
elevations.

The action of counter-recoil buffer is as follows:

As the buffer rod moves backward in piston rod the valve in buffer-rod
head is opened by the pressure of oil in back of valve and the vacuum
in front, which forces oil into buffer chamber in front of the
buffer-rod head. At full recoil the buffer chamber is full of oil and
buffer-rod head is inside the rear end of piston rod. When springs
force gun back in counter recoil, buffer rod moves forward, compressing
oil in chamber and forcing valve closed. This prevents escape of oil
through valve and forces oil to throttle between outside surface of
buffer-rod head and inside surface of piston rod, offering resistance
to spring action and thus easing the gun into battery. The inside bore
of piston rod is tapered at front end to increase resistance and obtain
desired decrease in counter-recoil velocity.

If guns fails to return to battery after a few rounds of rapid firing,
it is probably due to expansion of oil. This may be determined and
corrected by loosening filling plug. If oil spurts out, allow it to run
until gun is back in battery. It may be necessary to relieve oil two
or three times immediately after filling. Gun should never be allowed
to remain out of battery more than 1 inch on counter recoil without
determining and correcting the cause.

If gun remains out of battery and the relief of oil does not cause it
to return, it is due to:

(a) Weak or broken springs; (b) piston-rod gland too tight; (c) dirt or
lack of lubrication in gun slides; (d) distortion of gun on gun ways;
(e) distortion of piston rod due to improper counter recoil action.

The majority of cases are due to (a), (b) and (c).

(a) Can be determined only by removing springs, and should be
undertaken only after all other methods have been tried.

(b) Can be determined by loosening piston-rod gland. If gland is too
tight, gun will return to battery when it is loosened. If gland cannot
be loosened, piston-rod is probably distorted.

(c) Flood slides with oil, and if possible retract gun and examine gun
ways and slide for dirt.

(d) If possible allow gun to cool for 15 or 20 minutes. In case of (a),
(c) or (d) gun can generally be pushed back into battery by hand.

(e) If piston rod or interior mechanism is distorted, mechanism must
be disassembled and defective parts replaced. If distortion has
occurred, it can generally be identified by very rapid counter recoil
for round on which gun does not return to battery. This may be caused
by foreign matter in oil causing buffer valve to stick, or by lack of
sufficient oil. If distortion has occurred, it will be near gland and
can generally be felt by running hand along rod from bracket to gland.

[Illustration: 75 MM. GUN CARRIAGE MODEL OF 1916

VALVE TURNING GEAR AND RECOIL CYLINDER ASSEMBLED.]

In case of any improper functioning of recoil mechanism during recoil
or counter recoil, cease firing until cause has been determined and
corrected. A piece is out of action when recoil mechanism is not
operating properly and will almost certainly be damaged seriously if
further firing is attempted.

After dismounting any part of recoil mechanism or filling recoil
cylinder, gun is to be retracted and released to allow counter recoil
if possible. In performing this test, valve-turning mechanism must be
disconnected and valve turned to correspond to an elevation of carriage
of 53° before gun is retracted. Gun must not be held out of battery
more than 10 seconds before being released.

=Variable recoil= is obtained by varying the area of effective
throttling holes in the recoil valve. An arm on the trunnion cap is
connected by means of connecting rod, valve-turning arm, valve-turning
gear, and a piston-rod gear, to the piston rod itself. As the gun is
elevated the relation of the cylinder to the trunnion changes, causing
the piston rod to turn by means of the valve-turning mechanism. Slots
in the piston engage lands in the valve, causing the valve to turn with
the piston. As the cylinder remains stationary the location of the
lands inside of the cylinder change with relation to the three rows
of holes in the valve, and these rows of holes are covered to produce
variations in the length of recoil. At long recoil all the rows are
uncovered; at intermediate recoil one row is uncovered; and at short
recoil two rows are uncovered. The setting of the valve in degrees
elevation is shown by the scale on the piston-rod sleeve and index mark
on the edge of the piston-rod bracket bushing at the top of the piston
rod.

=The top carriage= carries trunnions of the spring cylinders and rests
on pintle bearing. The top carriage bears on the circular bronze slides
in upper part of pintle bearing and is centered on the bronze pintle
collar of the pintle bearing.

=The pintle bearing= carries the top carriage, the equalizing pinions
and the equalizing gear, and is supported by the axle arms, which are
shrunk in the arms of the pintle bearing. Axle arms bear in the wheels.

The object of the =equalizing gear= is to increase the stability of
the carriage in firing when the wheels are at different elevations.
Equalizing gear is an H-section with bevel tooth sector on each end and
bronze-bushed bearing in the center. It bears over the vertical journal
below the pintle bearing and is held in place by equalizing-gear
support screwed inside the journal. Vertical deflection is prevented
by the equalizing-gear bolts which are fixed to the pintle bearing
by means of nut and shoulder, pass through slots in equalizing gear,
and support gear on bolt heads. Equalizing pinions are bevel pinions
sectors, bronze bushed, bearing over the arms of the pintle bearing,
and have the lugs for trail connection bolts. Pinions are held in place
by locking rings screwed over axle arms and are free to revolve about
the pintle bearing arms.

Equalizing pinions mesh with equalizing gear.

When the carriage is laid with wheels at different elevations, it
is more unstable than when wheels are level. If fired under this
condition, the force of recoil tends to overturn the carriage. The
function of the equalizing gear is to overcome this tendency. When
carriage is fired, firing stresses are transmitted to trails, and
the side on which the smaller stress is exerted tends to rise. This
motion is transmitted through equalizing pinion and equalizing gear to
equalizing pinion on other side, applying downward force on this trail
and preserving the stability of carriage.

_The angle of site_ mechanism is designed to give the gun a maximum
depression of about 6° and a maximum elevation of 11°, independent of
the elevating mechanism. The mechanism is operated by two handwheels,
one on each side of gun.

[Illustration: 75 MM GUN CARRIAGE MODEL OF 1916.

DIAGRAM OF ANGLE OF SITE MECHANISM.]

Handwheel on right side operates through bevel gear on handwheel shaft
and intermediate shaft, both mounted in angle of site bracket, right,
and cross shaft mounted in bronze bushings in top carriage. Handwheel
on left side operates through bevel gears on handwheel shaft, mounted
in angle of site bracket, left, and cross shaft mounted in bronze
bushings in top carriage. Bevel gears on ends of both cross shafts mesh
with bevel gear on angle of site worm, which is mounted in bushings in
top carriage and held in place by angle of site-worm caps. This worm
meshes with teeth cut in rocker.

Rocker is a U-shaped piece with bearings at the tops of both arms
and teeth cut in bottom of U. The bearings bear over and are free to
revolve about trunnions on cradle independent of trunnion bearing in
top of carriage. Top half of right bearing is formed by rocker arm,
right, which extends back and carries angle of site scale, pointer,
rack, and level and forms a bearing for elevating handwheel shaft. Rear
of rocker arm, right, is braced by rocker arm brace, a diagonal hollow
rod attached to rocker arm and rocker. Top half of left bearing is
formed by rocker arm, left, a diagonal arm extending upward to the rear
to form a support for sight. Movement of the angle of site mechanism
is limited in elevation by the rocker stop bolted to the side of the
rocker and in depression by a screw in the arc.

=The elevating mechanism= is designed to allow an elevation of the
gun of 42° independent of the angle of site mechanism. The mechanism
is operated by one handwheel on the right side of carriage, which is
turned in a clockwise direction to elevate gun.

[Illustration: 75 MM GUN CARRIAGE, MODEL OF 1916.

ELEVATING MECHANISM.]

The elevating mechanism is operated through bevel gears on elevating
handwheel shaft mounted on a rocker arm, right, elevating intermediate
shaft inside rocker-arm brace, elevating cross shaft, mounted in an
elevating cross-shaft bearing bolted to the rocker, and the elevating
worm, which bears inside lower part of the rocker. The elevating worm
meshes with the elevating arc, which is bolted to the bottom of the
spring cylinder.

In indirect fire the angle of site in mils is laid off on the angle of
site scale with the pointer and the desired range of graduation brought
opposite the pointer by means of the elevating handwheel.

=Operation of the Angle of Site and Elevating Mechanism.= The angle of
site mechanism is operated by turning handwheel, the movement of which
is transmitted through the shafts and gears to the angle of site worm
meshing with the rocker. Movement of the rocker is transmitted directly
through the elevating worm, elevating arc, and spring cylinder to the
gun, and through the rocker arms to the elevating mechanism, gun,
cradle, and sights. The elevating mechanism moves only gun and cradle
through movement of handwheel shafts, and the elevating worm inside the
rocker, which meshes with the elevating arc.

The angle of site scale is graduated in mils from 170 to 500. The range
scale is graduated in meters. The zero setting of the gun is with O on
the range scale opposite 300 on the angle of site scale and the level
bubble on the rocker arm, right, at the center of the tube. This allows
the maximum depression of 7 degrees (about 130 mils) or the maximum
elevation of 11° of angle of site mechanism to be read on the angle of
site scale against the zero of the range scale.

The sight, model of 1916, which acts as a support for the panoramic or
peep sight, is attached to the rocker arm, left.

[Illustration: 75 MM. GUN CARRIAGE, MODEL OF 1916.

TRAVERSING MECHANISM.]

In direct fire, the axle of the bore is brought on the line of site
by operating the angle of site handwheel until the cross hairs of the
sight are on the target and the range is laid off independently by
bringing the desired range graduation opposite 300 on the angle of site
scale. Line of site may be set independent of the range, as there are
two angle of site handwheels.

=Traversing Mechanism.= The total traverse of the gun on the carriage
is 800 mils. The traversing handwheel is located on the left side of
the carriage and turns in a clockwise direction for left traverse.

The traversing handwheel shaft is mounted in the angle of site bracket,
left, and the angle of site bracket cover, left. A bevel pinion on
upper end of the shaft meshes with bevel gear on traversing shaft,
which bears in angle of site bracket, cover, left and intermediate
shaft bearing bolted to top carriage. A bevel pinion at lower end of
the intermediate shaft meshes with bevel gear on end of traversing-worm
shaft, which is mounted in bearing in top carriage. Traversing worm
meshes with traversing rack which is screwed to pintle bearing.
Traversing stops are filister head screws between end teeth of
traversing racks to limit movement of worm in rack.

The movement of handwheel is transmitted through shafts and bevel gears
to worm and rack. Rack is mounted in pintle bearing, which remains
stationary, and top carriage moves about its bearing in center of
pintle bearing and bronze-lined slides around the outside of pintle
bearing. Traversing scale is screwed to pintle bearing above rack, and
pointer is formed on traversing worm-shaft bearing.


DISMOUNTING AND ASSEMBLING CARRIAGE.

Note.—The first and most important precaution to be observed in
assembling guns and carriages is that all parts must be clean.

Where dismounting but not assembling operation is described, assembling
is approximately the reverse of dismounting.

     I.  To remove recoil cylinder.
    II.  To disassemble recoil cylinder.
   III.  To assemble recoil cylinder.
    IV.  To dismount gun.
     V.  To remove counter-recoil spring.
    VI.  To remove breechblock.
   VII.  To replace piston rod, gland pkg.
  VIII.  To remove wheel.
    IX.  To remove shields.
     X.  To remove spring cylinder.
    XI.  To remove sight.
   XII.  To remove rocker and rocker arms.
  XIII.  To remove top carriage.
   XIV.  To remove equalizing gear and pinions.
    XV.  To remove brake mechanism.
   XVI.  To remove trails.


I. To Remove Recoil Cylinder.

1. Remove valve turning gear cover (take out four ⅜” bolts attaching it
to the piston rod bracket).

2. Remove valve turning gear, valve turning arm and connecting-rod as a
unit by removing split pin, nut, and connecting rod pin from trunnion
cap, right.

3. Remove piston rod (remove lash wire and two 3/16” split pins) slide
piston rod gear forward and remove.

4. Remove ¼” locking screw from top of piston rod bracket.

5. Remove 3/16” cylinder retainer screw and loosen cylinder retainer,
but do not remove retainer.

6. Remove brass spring-rod plugs from rear ends of both spring rods.

7. Screw spring compressor eye into rear of left spring rod. Make loop
in compressor and attach double sheave close to cradle. Attach single
sheave to lunette by means of loose cord of sheave rope.

8. Man pulling rope with from four to six men, retract gun not less
than 10”, and secure rope to lunette.

9. Remove cylinder retainer, slide cylinder forward until free of
groove in gun and remove cylinder. Handle carefully.

10. Allow gun to return to battery slowly by slacking off on pull rope.


II. To Disassemble Recoil Cylinder.

Note.—The interior parts of recoil cylinder are made with great
accuracy to insure proper operation and must be handled with care to
avoid injury.

1. Remove recoil cylinder from carriage. (See I.)

2. Drain recoil cylinder by resting on blocks at front and rear,
removing both filling plugs and drain plug, and tipping rear end up to
allow all oil to flow out of drain-plug hole.

3. Unscrew buffer-rod nut from rear cylinder head, draw out buffer rod
until wrench can be applied on flats, and remove nut. Push rod back
into cylinder.

4. Remove lower split pin from gland lock, swing gland lock back until
free of notches in gland, and loosen gland with gland wrench. Unscrew
front cylinder head with special wrench. Threads may be started by
striking handle of wrench with soft hammer. Do not hold cylinder in a
vise.

5. Draw out piston rod slowly, supporting it at both ends as it leaves
cylinder. Hold recoil valve in cylinder with ends of fingers. Keep
receptacle under front of cylinder to catch surplus oil.

6. Drain surplus oil from piston rod by holding vertically over
receptacle with piston down and holding buffer rod in place.

7. Rest piston rod on blocks, remove buffer-bushing locking screw, and
unscrew buffer bushing, holding piston rod by wrench on flats at front
end of rod. Have supporting blocks under both ends of rod so that rod
will not be strained.

8. Draw out buffer rod carefully.

9. Draw out recoil valve with fingers. Remaining parts can now be
easily disassembled. Buffer head is locked in place with bronze pin,
which must be driven out before head can be unscrewed.


III. To Assemble Recoil Cylinder.

This operation is the reverse of II. Be sure that all gaskets and
locking screws and pins are replaced and are in good condition. Be sure
that all parts of mechanism are perfectly clean and dry, and that oil
is clean. Oil must be strained through double thickness of clean cloth
and if clean oil is not available use new oil. Do not make piston-rod
gland too tight. Tighten with hand and screw up with wrench one
additional notch to lock gland. Fill recoil cylinder before replacing
on carriage, as follows:

(a) With drain plug in place and filling plugs out, pour hydroline oil
into filling hole slowly to avoid the formation of air bubbles.

(b) When oil is level in filling-plug openings, tilt cylinder slightly
to allow escape of air and replenish oil.

(c) Loosen filling plug in front end of piston rod enough to allow oil
to drip, and tighten plug.

(d) Replace rear filling plug, raise front of cylinder about 6 inches,
and tap cylinder lightly with wood block or lead hammer to remove air.
Level cylinder, fill, and replace front filling plug. Be sure that all
gaskets are in place and properly centered.

Note.—After recoil mechanism has been disassembled and replaced on
carriage gun should be retracted 46 inches and eased back into battery
slowly to be sure that it is properly reassembled.


IV. To Dismount Gun.

1. Remove recoil cylinder (see I) and breechblock (see VI).

2. Raise and block up trails in horizontal position, elevate gun until
axis of bore is parallel with trails, and attach retracting mechanism
(see I-7) to left spring rod, retract gun about 6 inches, remove
3-16-inch split pin in left spring-rod key, and drive out key with
bronze drift. Ease gun into battery slowly and permit further forward
movement of spring rod until rope is slack and front end of spring-rod
rests against spring cylinder cover.

3. Transfer retracting apparatus to right spring-rod, retract gun about
¼ inch, remove split pin and spring-rod key, ease gun into battery
until spring-rod rests against spring-cylinder cover, and detach
retracting mechanism.

Note.—In this position full pressure of springs is against cylinder
cover and gun is free to slide in ways. Men should be kept from in
front of spring-cylinder and care must be exercised to prevent tipping
of cradle to the rear, which may cause gun to slide off.

4. Bring gun to maximum depression.

5. Lower trails to ground, spread trails against wheels, set brake, and
bring gun to zero elevation.

6. Requires seven men and four pick handles or implements of almost
the same length and strength. Slide gun about 36 inches to the rear
by hand, place one pick handle in bore of gun at breech with one man,
one pick handle with a man on each side under gun slides at front of
cradle, and four men with two pick handles under gun as gun is drawn
out.

7. Push gun out of ways, supported by men, and remove.

Note.—In using pick handles do not place them under dust guards at gun
lugs. Care must be taken to keep gun properly supported at same level
as cradle guides at all points until free of guides.

In remounting gun on cradle be sure that ways are well oiled and ways
and slides thoroughly clean. Mounting gun is the reverse of IV.


V. To Remove Counter-recoil Springs.

1. Close and latch trails. (Open spring-cylinder cover.)

2. Set brake and drive one spade (to secure carriage).

3. Remove breechblock (see VI.)

4. Attach spring-compressor to right spring rod (see I-7).

5. Secure single block of retracting apparatus to fixed point, such
as “dead man,” driven spade, or tree. The holding power of this fixed
point must be at least equivalent to a driven spade and attaching point
of rope should not be higher than center of spring rod.

Note.—Sufficient slack of rope must be allowed to permit spring
compressor to travel full length of spring cylinder and be detached
from spring rod at front end.

6. Retract gun about 6 inches, remove split pin in spring-rod key and
drive out spring-rod key with bronze drift.

7. Release retracting mechanism gradually until spring compressor rope
is slack, draw spring rod out of front end of spring cylinder, and
detach spring compressor.

8. Attach retracting mechanism to spring rod, right.

9. Retract spring rod about ½ inch, remove split pin, and drive out
spring-rod key.

10. Release retracting mechanism gradually until spring compressor
rope is slack, draw spring rod out of front end of spring-cylinder and
detach spring compressor.

Note.—Assembly of counter-recoil springs is reverse of removal. The
following precautions must be observed in assembling:

(a) If tension-spring compressor brings spring rod up solid against
spring cylinder bushing in rear of spring cylinder, ease off rope
slightly and pry up rod with bronze drift until it will enter the
bushing.

(b) Before key slot enters gun lug see that keyways in spring-rods and
keyways in gun lugs are in line. If not, turn spring-rod by means of
drift until keyways are in line.


VI. To Remove Breechblock.

1. Remove operating-shaft detent, slide operating handle to the right
as far as the chain will permit, remove 1-16 inch split pin from
studlink pin.

2. Remove chain, piston rod, spring piston, piston-rod nut, and locknut
as a unit by drawing out of closing-spring case.

3. Remove closing spring from case.

Note.—For complete instructions regarding disassembly of the breech
mechanism see page 19.

4. Remove trigger-shaft detent split pin and trigger-shaft detent by
drawing it out of the breechblock to the right.

5. Remove trigger shaft by prying gently straight down with screw
driver or similar tool. Keep breechblock supported for all succeeding
operations.

6. Remove operating handle by sliding to the right and off operating
shaft.

7. Remove operating shaft by sliding to the left.

8. Raise breechblock as far as possible (about 3-8 inch), move bottom
part of operating arm to the rear, and remove operating arm.

9. Remove breechblock by sliding down free of breech ring.

10. Remove extractors by sliding toward center line of gun.


VII. To Replace Piston Rod Gland Packing.

(Packing, 4 rings, 5-16-inch square Garlock hydraulic packing.)

(Gun in battery or cylinder removed.)

1. Remove lower split pin from gland lock, swing gland lock up out of
notch in gland.

2. Unscrew gland with special wrench and slide forward on rod.

3. Remove packing with bent wire.

4. Insert five rings of new packing, one ring at a time, and push each
ring home with packing tool of copper or hardwood to fit into gland
recess. Break joints in rings and tap packing tool lightly with hammer
to drive each ring of packing home.

5. Screw up gland by hand and not more than three additional notches
with wrench so that gland lock will catch and replace split pin.

Note.—For the first few rounds after inserting new packing there will
be some leakage at gland and occasional tightening will be necessary.
Gland should not be screwed up tight with a wrench, as it can be made
sufficiently tight by hand to prevent leakage if properly packed.


VIII. To Remove Wheel.

1. Raise and support carriage under equalizing gear near each end
(about 12” each side of center.)

2. Disengage hubcap latch; unscrew and remove hubcap.

3. Disengage wheel fastening plunger and remove wheel fastening.

4. Remove wheel.


IX. To Remove Shields.

A. Top shield.—1. Remove four ⅜” pins, two ⅜” locking pins, and lift
off shield.

B. Apron.—1. Remove four ⅜” hinge pins and remove apron.

C. Cradle Shield.—1. Remove two 3/32” split pins, nuts and bolts. On
carriages number 625 to number 678 inclusive, remove two cradle shield
extensions.

D. Main Shield, left.—1. Remove six ½” bolts from shield bracket outer
left. 2. Remove three ⅜” bolts from shield socket, inner left. 3. Lift
off shield.

Main Shield, right—1. Remove right wheel (see VII). 2. Remove ½” pin
from brake band end, remove adjusting nut and force (by hand) brake
band out of position, to clear main shield, right. 3. Remove four ½”
bolts from shield bracket, outer right, and two ½” bolts from brake
lever bracket. Remove two 2/16” bolts from tool and remove tool
carrier. Remove three ⅜” bolts from shield bracket, inner right. 4.
Lift out shield.


X. To Remove Spring Cylinder.

1. Remove recoil cylinder (I), gun (IV), counter recoil springs (V),
sight (XI) and shields (IX).

2. Remove trunnion caps (right and left) by raking out four split pins,
loosening swing bolt nuts, and withdrawing ½” trunnion cap pins.

3. Remove rocker stops (right and left) by taking out four split pins
and ⅜” bolts.

4. Unlatch and spread trails.

Note.—Seven men and four pick handles (or similar implements) are
required for succeeding operations.

5. Post two men with one pick handle at rear, two men with one pick
handle immediately in front of elevating arc, and two men with one pick
handle at front end of spring cylinder.

6. Raise cradle slowly, slightly to the rear until rocker clears top
carriage. Carry to the rear sufficiently to rest middle pick handle
in trunnions and transfer two men with handle to rear of carriage.
Continue to the rear sufficiently to rest front pick handle in
trunnions, transfer men to rear, and remove spring cylinder.


XI. To Remove Sight.

1. Remove three ⅜” bolts from rocker arm, left.

2. Remove one ⅜” pin from sight lever in left trunnion.

3. Remove sight and sight link.


XII. To Remove Rocker and Rocker Arms.

1. Remove spring cylinder (see X).

2. Remove two 3/32” split pins, with ⅜” nuts and bolts, two ⅜” cap
screws with lock washers, four ⅛” screws, driving out four O.247” by
O.34” by O.872” keys from rocker arms, right and left.

3. Remove rocker arm, left, by sliding up and out of rocker.

4. Remove cross-shaft bearing cover by taking out three 3/32” split
pins and removing three 3/16” nuts.

5. Drive out ⅛” pin from intermediate shaft pinion, remove two ⅛”
split pins, two ½” nuts, one ⅛” split pin, and one ½” cap screw from
rocker-arm cap and remove rocker-arm cap.

6. Lift out elevating handwheel and handwheel shaft as a unit.

7. Draw intermediate shaft up and out of rocker-arm brace, draw rocker
down from trunnions (keeping in line with rocker-arm bearings) and
remove. Swing rocker arm, right, up and around trunnions until free of
range-scale bracket and remove.


XIII. To Remove Top Carriage.

1. Remove spring cylinder (see X) rocker and rocker arms (see XII).

2. Remove angle of site bracket, left, by removing three split pins
and nuts from ⅜” bolts in angle of site bracket cover, left, taking
off cover, removing nut and split pin from traversing handwheel shaft,
removing handwheel and drawing shaft out to the left.

3. Remove two split pins and ¼” nuts from cross shaft pinion case
(left) bolts, extract bolts, and remove case.

4. Remove cross shaft pinion case, right, as in XIII-3.

5. Remove split pins and two nuts from cross shafts, right and left.

6. Remove split pins and nuts from four ½” studs securing angle of site
bracket, left, and remove bracket with attached parts as a unit.

7. Remove angle of site bracket, right, as in XII-5.

8. Draw out cross shafts, right and left, and remove cross shaft
pinions, right and left.

9. Traverse top carriage to the right (by turning intermediate shaft
gear by hand) sufficiently to allow traversing stop, rear to be
removed. Extract split pin, remove nut, and take off traversing stop,
rear.

10. Traverse top carriage to the left until traversing worm is
disengaged from rack, remove split pins and nuts from four studs
securing traversing worm shaft bearing to top carriage, and remove
bearing and attached parts as a unit.

11. Lift out traversing worm with attached parts as a unit.

12. Turn top carriage to the right 90 degrees from zero azimuth, remove
three screws that attach traversing rack to pintle bearing and remove
traversing rack.

13. Turn top carriage to the right 90 degrees (180 degrees from zero
azimuth), remove four screws that attach dust guard to pintle bearing
and remove dust guard.

14. Remove two screws that secure clip to pintle bearing and take off
clip.

15. Raise top carriage from pintle bearing.


XIV. To Remove Equalizing Gear and Pinions.

1. Remove top carriage (see XIII), wheels (see VIII), brake mechanism
(see XV) and trails (see XVI).

2. Turn pintle bearing bottom side up, remove 29 screws which attach
washers and binders and remove equalizing-gear cover.

3. Remove split pins and nuts from both locking ring-clamp bolts,
unscrew and remove rings (one right, one left).

4. Slide equalizing pinion off axle arms.

5. Remove split pins from right equalizing-gear bolts, hold nuts
tight, unscrew and remove bolt, remove nut and washer, remove left
equalizing-gear bolt, nut, and washer in the same manner.

6. Remove locking screw and equalizing-gear support (using special
wrench). Lift up and remove equalizing gear.


XV. To Remove Brake Mechanism.

1. Remove wheels (see VIII).

2. Remove brake bands, right and left, by extracting four split pins
and removing four brake pins from ends of brake shaft.

3. Remove one split pin from each type “A” pin securing brake lever,
foot to brake lever bracket and to sleeve extension. Remove type “A”
pins and brake lever.

4. Extract two split pins from brake lever sleeve near center of
carriage, draw out and remove brake shaft, left.

5. Remove shield bracket, outer right, brake shaft, right and brake
lever sleeve with all permanent parts attached, by removing main shield
(see IX, D and E), removing split pin and nut from brakehanger bolt,
taking out bolt, and sliding parts off axle arm.

6. Remove shield bracket, outer left, by removing split-pin, nut,
and brake hanger bolt and sliding brake hanger with permanent parts
attached, off axle arm.


XVI. To Remove Trails.

1. Support carriage at front of pintle bearing.

2. Remove two split pins and nuts from connection bolts, drive out
bolts with copper drift, slide trails to the rear and remove.


GENERAL INSTRUCTIONS.


Filling Recoil Cylinder (Cylinder Mounted on Carriage.)

If the recoil cylinder is not completely filled, loss of stability will
occur and there is danger of serious damage to material. Before firing,
a commissioned officer should always verify the filling of cylinder by
removing one filling plug (with gun level) in which case oil should be
visible above recoil valve.

To fill recoil cylinder when assembled to carriage, elevate the gun
about five degrees, remove both filling plugs and pour Hydroline oil
in slowly with funnel until oil appears at rear filling plug hole.
Level gun and again fill until oil appears at both filling holes. Shake
carriage gently and continue to refill slowly until air ceases to come
out of cylinder. Replace rear plug, elevate gun about five degrees,
remove valve turn-gear cover, and loosen plug in end of piston rod
sufficiently to allow oil to drip out. As soon as oil starts to drip,
tighten plug; be sure that gasket is centered. Replace rear filling
plug, rock carriage to permit air to escape from filling hole and fill
with oil. Replace plug, level gun, and perform same operation with rear
filling hole. When air is all out of cylinder, tighten both plugs and
elevate to five degrees, allow to stand for about five minutes, then
remove front plug and again refill. Loosen drain plug and drain out
about ¼-gill of oil into receptacle. Do not allow oil to run down into
gun slides.

About four quarts of Hydroline oil is required to fill recoil cylinder.
Oil must be clean and free from dirt and should be strained through
clean linen or muslin cloth before using.

In emergencies glycerin and water, or any buffer or engine oils may be
used in recoil cylinders, but should be replaced by Hydroline as soon
as possible. Where the above liquids are used, all interior parts of
recoil mechanism must be emptied, disassembled, thoroughly cleaned and
dried before refilling.




CHAPTER VIII

75-MM FIELD GUN MODEL 1917 (BRITISH).


Weights and Dimensions.

  Weight                          995 lbs.
  Caliber                        2.95 in.
  Total length                  88.21 in.
  Length of bore               83.915 in.
  Length of rifled portion      72.72 in.
  Rifling 24 grooves, right hand twist, zero turns at the origin
      to 1 turn in 75 in. (25.4 calibers) at 9.72 in. from the
      muzzle thence uniform.


The Carriage.

  Weight of carriage, complete                        1950 lbs.
  Weight of gun and carriage complete                 2945 lbs.
  Weight at end of trail carriage limbered              96 lbs.
  Diameter of wheels                                     56 in.
  Width of track                                         60 in.
  Length of recoil                                       49 in.
  Maximum angle of elevation                         16 degrees
  Maximum angle of depression                         5 degrees
  Maximum amount of traverse of gun on the carriage    142 mils


DESCRIPTION.

_The gun_ is a combination of a built up and a wire wrapped gun. It
consists of a tube, a series of layers of steel wire, jacket and
breech ring. The tube extends from the rear end of the chamber to the
muzzle. Over the rear portion of the tube are wound 15 layers of O.04
by O.25” steel wire. The jacket is fitted over the wire and the tube,
and is secured longitudinally by corresponding shoulders and the
breech ring, which is screwed over the jacket at the rear, and secured
by a set screw. The breech ring is prepared for the reception of the
breech mechanism, and is provided on the upper side with a lug for the
attachment of the hydraulic buffer.

[Illustration: _75 mm. Field Gun, Model of 1917 (British)._]

[Illustration: _75 mm Field Gun, Model of 1917_ (_British_)

_Breech Mechanism Assembled_]

_The breechblock_ is of the swinging type, interrupted screw with two
threaded and two slotted sectors instead of the four we are familiar
with in the 3”. The firing mechanism is of the continuous pull type.

The ammunition used is similar to that used with the American and
French types of 75s.


=The Principal Parts of the Carriage are=:

  Trail
  Top Carriage
  Cradle
  Recoil cylinder
  Springs
  Elevating gear
  Range gear
  Traversing gear
  Firing Mechanism
  Brakes
  Shield
  Axle and wheels
  Sights
  Gravity tank

=The trail= is tubular. The top carriage houses bearings to receive the
cradle trunnions and in travel it is locked to the trail. The bronze
cradle pivots on the top carriage. The cradle trunnions support the
sight.

=The recoil system= is of the hydraulic-spring type. The recoil
cylinder is surrounded by the counter-recoil springs which in turn
are enclosed by a steel case—all of which is screwed on top of the
cradle above the gun. The system operates in the same manner as the 3”
materiel with the exception that it possesses the additional feature of
a gravity tank which replaces oil lost during firing.

[Illustration: _75-mm. Gun Carriage, Model of 1917._ (_British_)

  _Recoil Controlling System_
]

[Illustration: _75 mm. Gun Carriage, Model of 1917._ (_British_)

_Plan_]

=The elevating mechanism= is of the doubled-ended screw type with the
independent angle of site. The gears are so arranged that the elevation
for range can be made without disturbing the laying for difference
in elevation of the gun and the target, that is, the line of sight.
The handwheel on the right is for range to the target while the
handwheel on the left is for the angle of site.

=The traversing mechanism= is of the pintle type, consisting of a
crosshead, link nut, and an actuating screw with a handwheel. It
permits of a 72 mil. traverse either side of the center. A scale strip
and a pointer indicate the angle of traverse.

=The firing mechanism= like that of the American 75 is located on the
left side of the gun instead of the right side as on the 3” and the
French 75. The gun can be fired when it is within 2 inches of the “in
battery” position, which increases the possible speed of firing.




CHAPTER IX

THE 4.7” RIFLE, MODEL 1906.

GUN.


Weights and Dimensions.

  Weight                                     2,688 lb.
  Caliber                                      4.7 in.
  Total length                              134.92 in.
  Length of bore                            129.42 in.
  Length of rifling                          111.9 in.
  Number of grooves                                 42
  Twist                                    Right hand.
  Weight of proj. based fuse                    60 lb.
  Weight of proj. point fuse                    45 lb.
  Weight of powder charge                       95 oz.
  Muzzle velocity, 60 lb. proj.   1,700 ft. per second
  Muzzle velocity, 45 lb. proj.   2,050 ft. per second
  Maximum range                          11,000 meters


THE CARRIAGE.

  Weight of carriage complete           5,320 pounds
  Weight of carriage and gun complete   8,068 pounds
  Maximum elevation                       15 degrees
  Maximum depression                       5 degrees
  Maximum traverse                         140 mils.

=The gun= is built up and consists of a tube, jacket, locking hoop and
clip. The jacket covers the rear half of the tube and projects beyond
the tube at the rear to form the breech recess. The jacket also has a
recoil lug on the under side for connecting the recoil cylinder. The
clip is a short hoop near the muzzle and has guides formed on it
to guide the gun in the cradle on recoil. The jacket also has guides
formed on it. The length of the gun is approximately 11 feet.

[Illustration: 4.7” Rifle]

=The breechblock= is of the interrupted screw type having four threaded
and four plain sectors. It is operated by a handle which swings from
left to right turning and withdrawing the breech with one motion. An
extractor is fitted for throwing out the shell case when the breech is
opened after firing.

The firing mechanism is of the type known as a continuous pull
mechanism, that is, the mechanism is cocked and fired by the pull on
the lanyard or by downward pressure on the firing handle located at the
right side of the breech.

The recoil system is of the hydro-spring type.

The two parallel steel tubes (the spring cylinders) are fitted into a
frame surmounted by heavy steel rails which form the gun slides thus
forming the cradle. The recoil cylinder is fitted between these two.

The recoil and counter-recoil piston rods are attached to the gun lug
and recoil with the gun, while the spring cylinders and recoil cylinder
remain stationary.

The recoil is constant, being 70 inches for all elevations. The
recoil cylinder uses hydroline oil as the buffer medium. Throttling
is obtained by three throttling bars running lengthwise of the
cylinder which are of varying height to give a throttling effect with
corresponding slots in the recoil piston. A counter-recoil buffer is
fitted in the piston rod to take up the shock when the springs return
the gun into battery.

The trunnions on the cradle are mounted in bearings formed by a yoke
which swivels in a pintle bearing provided at the front of the trail.

_Traverse_ is obtained by means of a handwheel and screw mounted on the
left side of the trail which swings the yoke in traverse carrying the
gun with it. A traverse of 70 mils on each side of center is possible.

_The piece is elevated_ by a double screw type of mechanism. The upper
end is attached to the cradle and so raises and lowers it. The screw is
operated thru gearing by two handwheels one on each side of the trail
from 5° elevation dep. to 15° elevation.

_The trail_ is of the solid type made up of flasks of channel section.
It has housings for the axle and carries the pintle bearing in which
the top carriage or yoke swings. A tool box is provided in the trail.
A seat is provided on each side of the trail for the cannoneers. The
lunette transom is fitted about 27 inches from the rear of the trail
and carries a bearing that fits the limber pintle.

A trail prop is provided for supporting the trail when limbering.

The spade can be released and folded up on the trail when traveling.

A traveling lock is provided on the trail for locking the gun when
traveling. The piston rod and spring rods must be disconnected before
the gun can be drawn back far enough to lock.

_The wheels_ are 61 × 6 inch with rubber tires and band brakes. Some
older vehicles have steel tires and are fitted with tire brakes.

An armor plate _shield_ is fitted to the carriage for the protection of
the personnel.

_The instruments for sighting_ and laying the piece included a line
sight, a rear sight, a front sight, a panoramic sight and a range
quadrant.

The line sight consists of a conical point as a front sight and a V
notch as a rear sight. These are located on the Jacket of the gun, and
are useful for giving a general direction to the gun.

[Illustration: 4.7” Rifle]

The sighting is similar to the 3”, 1902.

The rear sight and front sight are used for direct aiming. The rear
sight is a peep sight mounted on a range scale quadrant by a bracket
on right side of the cradle. The front sight is a pair of cross wires
mounted in a ring attached by a bracket on the cradle about 3 ft. ahead
of the rear sight.

The range scale quadrant has a socket in which the Standard U. S.
Panoramic sight may be mounted.

For indirect fire the gunner on the left of the carriage lays for
direction only.

On the right side of the cradle is mounted the Range Quadrant which
has in combination with it the Angle of Site Mechanism. For indirect
fire the gunner on the right of the piece lays for range with this
instrument.

=Fixed ammunition= is used with this gun. Shrapnel and high explosive
shell are used. The base fuzed steel shell and the shrapnel weigh 60
lbs. The point fuzed steel shell weighs 45 lbs. Gas shell are also
issued identical with the 45 lb. steel shell.




CHAPTER X

THE 155-MM FILLOUX GUN.


WEIGHTS, DIMENSIONS, ETC.

  Weight of Gun including breech
      mechanism                           8,795 lbs.
  Length                                  232.87 inches.
  Caliber                                 155-mm (6.1042 inches.)
  Muzzle velocity                         2,380 ft.-sec.
  Rifling, one turn in 2.989. Caliber,
      right hand uniform.
  Weight of projectile                    95 lbs.
  Maximum range                           16,200 meters.
  Weight of maximum powder charge         25¼ lbs.
  Weight of carriage                      11,065 lbs.
  Weight of gun and carriage, complete    19,860 lbs.
  Diameter of wheels                      1,160mm.
  Width of track                          2,250 mm.
  Height of axis of gun                   1,482 mm.
  Elevation                               0 to 35 degrees.
  Maximum traverse                        60 degrees.
  Weight of limber complete               3,190 lbs.
  Weight of gun carriage and limber       23,050 lbs.
  The distance from center line of
      carriage axle to center line of
      limber axle, approximately          4,500 mm.

[Illustration: _155 M.M. GUN_ _MODEL OF 1918_ (_FILLOUX_)]

_The gun_ is of the built-up type and consists of the tube strengthened
by the following jackets and hoops beginning at the breech end: The
breech ring, the jacket, the hoop A, the hoop B, the clip hoop, the
clip hoop set on the hoop B and the muzzle bell. The length of the gun
from the muzzle to the breech base is approximately 18½ feet.

A recoil lug on the underside of the breech ring provides means of
attaching the recoil and recuperator rods. Hinge lugs for the breech
are also formed on the breech ring. Bronze clips to serve as guides in
the cradle are screwed to the sides of the jackets.

_The breechblock_ is of the interrupted screw type, having four plain
and four threaded sectors. The breech mechanism is of the plastic
obturator type, having the forward mushroom-shaped head of the
breechblock equipped with the asbestos ring, known as the obturator
pad. Upon firing, this ring is compressed and acts as a gas check to
prevent the leakage of powder gases back through the breech. It has
sufficient resiliency to resume its original form after firing. The
firing mechanism is of the French percussion primer type which is
described under “155-mm Schneider howitzer” and is interchangeable with
the guns enumerated therein.

_The cradle_ is a steel forging pivoted by trunnions in the trunnion
bearings of the top carriage. It is bored with three parallel cylinders
for housing the recoil and recuperator mechanism. On its upper side are
slots for the gun slides and the elevating rack is bolted to the lower
side.

_The recoil mechanism_ is of the hydro-pneumatic variable recoil
type. The larger of the three cylindrical bores in the cradle block
contains the recoil mechanism; the two smaller ones, the parts of the
recuperator mechanism.

[Illustration: 155 MM GUN CARRIAGE MODEL OF 1918 (FILLOUX)

LONGITUDINAL SECTION IN BATTERY]

_The recoil mechanism_ consists of a piston and piston rod and a
counter rod. The piston rod is connected to the breech lug and,
therefore, recoils with the gun. Grooves of variable depth are
milled along the length of the counter rod, controlling the flow of
oil through the ports of the piston during the recoil. This counter
rod assembles within the bore of the piston rod. It does not move
longitudinally, but rotates. The amount of this rotation changes the
area of the orifices through which the oil can pass. Its rotation is
accomplished as the gun is elevated by means of an arm and gear sectors
in such a manner as to shorten the recoil as the gun elevates.

A replenisher or gravity tank is provided in connection with the recoil
cylinder which assures the recoil cylinder being full at all times
and also takes care of any expansion of the oil due to heating. Its
capacity is about 17 quarts.

_The recuperator mechanism_ consists of two connected cylinders, one
containing the piston and piston rod which are attached to the breech
lug, while the other contains a mushroom valve and a diaphragm. The
diaphragm separates the oil contained in the first cylinder and part
of the second cylinder from the high pressure air which compels the
return of the gun into battery after recoil. Normally a small amount of
oil must be between the valve and diaphragm. Oleonapth is the liquid
used in this recoil mechanism. The amount of oil in the recoil and
recuperator mechanism is shown by an indicator so that it can always be
seen whether or not they need filling.

_The top carriage_ is a large steel casting mounted on the bottom
carriage on which it pivots to traverse the piece.

The handwheels and mechanism for both elevating and traversing, are
mounted on the top carriage. The tipping parts are carried on the
trunnions of the top carriage.

Belleville Springs carry the weight of the gun when traversing, but on
firing the springs compress and the firing stresses are taken on the
bearing surfaces between the top and bottom carriages.

The bottom carriage is a large steel casting suspended from the axle
(in traveling position) by a heavy multiple leaf spring. It supports
the top carriage, houses the axle and provides hinge connections for
the trail. When firing the axle is unshackled from the left spring and
the bottom carriage bears directly on the axle.

_Traversing_ is accomplished by turning the top carriage which pivots
on the bottom carriage. This is done by means of a rack and train of
gears which are operated by the handwheel on the left side of the
carriage. A traverse of 60 degrees, 30 degrees right and 30 degrees
left, is possible.

_Elevating_ is accomplished by a rack on the cradle operated through
gears by the handwheel located on the gear box at the left of the top
carriage. Elevations from 0 degrees to 35 degrees can be obtained.

_The trail_ is of the split type and consists of steel plate beams
of box section. Locks are pivoted at the forward end of the trails
for securing them in the open position. When closed together they are
clamped and attached to the limber. A traveling lock is provided on the
trail for retaining the gun in retracted position.

Two types of spade are pivoted, one for soft and one for hard ground.
When traveling the spades are always removed from the trail.

_The wheels_ are of cast steel, each wheel having two solid rubber
tires.

Wheel shoes for traveling over soft ground are provided, which assemble
over the rubber tires. They consist of twelve plates for each wheel
which give a broad bearing surface under the wheel. The wheels are
equipped with band brakes.

_The sighting equipment_ is exactly the same as that described with the
155-mm Schneider howitzer.

_The ammunition_ used is of the separate loading type. Either shrapnel
or high explosive steel shell is used, as well as gas shells and other
special ammunition. The projectile weighs 95 lbs. The propelling charge
of smokeless powder is a sectionalized charge made up of two sections;
a base charge and one smaller increment. The weight of the charge is
25 lbs.

The fuzes commonly used are the 31 sec. combination fuse for use
with shrapnel and combining time and percussion elements: the point
detonating fuse Mark IV used with the steel high explosive shell and
the mark III point detonating fuze used with gas shell.

[Illustration: 155-MM. HOWITZER CARRIAGE, MODEL OF 1918 (SCHNEIDER).
TRAVELING POSITION.]

[Illustration: 155-MM. HOWITZER CARRIAGE, MODEL OF 1918 (SCHNEIDER).
RIGHT SIDE VIEW.]




CHAPTER XI

THE 155 HOWITZER, MODEL 1918


THE HOWITZER.


Weights and Dimensions.

  Material                               Alloy steel.
  Weight (including breech mechanism)    1,248 kg.—2,745 lbs.
  Caliber                                155-mm.—6.1 inch.
  Total length                           2,332-mm.—91.8 inch.
  Length of bore                         2,177-mm.—85.7 inch.
  Length of rifled portion of bore       737-mm.—68.4 inch.
  Rifling
      Number of grooves                  48.
  Width of grooves                       7.145-mm.—0.2813 inch.
      Depth of grooves                   1-mm.—0.03937 inch.
      Width of lands                     3-mm.—0.1181 inch.
      Twist, right hand, uniform,
          one turn in 25.586 cal.
  Powder chamber:
      Diameter                           158.75-mm.—6.25 inch.
      Length                             339.85-mm.—13.38 inch.
      Volume                             6,965.75 cu. in.—425 cu. in.
  Obturation                             Pad.
  Firing mechanism                       Percussion.


General Description.

The 155-mm howitzer, Model of 1918 (Schneider) is of the
hydro-pneumatic long recoil type, which may be used for direct fire,
but was specially designed for siege fire. On account of its high
trajectory it is able to direct shells on targets inaccessible to
standard 6-inch howitzers of limited elevation.

This howitzer has given satisfactory results in service and has proven
to be more superior than guns of similar caliber. It has a muzzle
velocity of 1,480 foot-seconds and attains a maximum range of 12,600
yards, the projectile weighing about 95 pounds.

A maximum rate of fire of four or five rounds per minute may be
attained, but heating as well as difficulty of preparing and
transporting the ammunition by the gun crew renders such rate
impossible for more than a few minutes. However, the normal rate of
fire is two per minute and may be loaded at any degree of elevation.

The howitzer is mounted on a sleigh and rigidly secured by means of a
breech key and the holding down band. The sleigh contains the recoil
and recuperator mechanisms which permits long recoil and insures
stability at low elevations. When the gun is fired the sleigh recoils
on bronze slides on the cradle, which is a U-shaped steel plate and
rests in the trunnion bearings of the trail.

This howitzer may be elevated from 0 degrees to 42 degrees by means of
the elevating mechanism. The traverse is 52.2 mils right and left, the
carriage sliding on the axle and pivoting on the spade, which prevents
the carriage recoiling when the gun is fired. The customary shield
protects the gunners from flying shrapnel and fragments.

[Illustration: _155 M.M. HOWITZER MODEL OF 1918_ (_SCHNEIDER_)]

In traveling position the howitzer is retracted and locked to the
cradle, the cradle locked to the trail, the spade revolved and secured
to the bottom of the trail. The lower end of trail rests on the
carriage limber, which is used to carry the proportionate share of the
load of the howitzer and carriage in traveling position. The limber is
equipped with a connecting pole for motor traction. The carriage and
limber wheels are rubber tired and considered able to negotiate any
roads suitable for field artillery.


Howitzer Description.

The howitzer, consists of a tube and jacket. =The jacket= is shrunk
over, approximately, the rear half of the =tube= and screwed to it by
a short thread near the rear end of the tube. The rear end of the tube
is prepared for the reception of the breechblock. On the right of the
jacket at its rear are two lugs which receive the hinge pintle of the
operation lever. A flat seat with two transverse slots is machined on
the top of the jacket at the rear end for receiving the counterweight.
=The counterweight= is securely fastened to the jacket by six screws,
and two lugs which engage the slots in the jacket. =The bridle= is
fitted to the underside of the jacket near the rear end and held in
place by four screws. The breech key passes through the bridle and
holds the howitzer in its seat on the sleigh. On the underside of the
jacket just forward of the bridle seat are seven square threads which
engage corresponding threads on the sleigh. A holding-down band which
encircles the jacket at its forward end also secures the howitzer to
the sleigh.

On the top surface of the counterweight are two nickel silver leveling
plates.

Vertical and horizontal axis lines are cut on the breech and muzzle
faces. A line showing the actual center of gravity with the breech
mechanism in place is cut on the upper side of the jacket marked C. of
G. The name and model of the howitzer are stamped on the left side of
the jacket just below the counterweight. The name of the manufacturer,
year of manufacture, serial number of the howitzer and the weight of
the howitzer, including the breech mechanism, are stamped on the muzzle
face.

[Illustration: _155 M.M. HOWITZER MODEL OF 1918_ (_SCHNEIDER_)

_BREECH MECHANISM ASSEMBLY_]

[Illustration: _155 M.M. HOWITZER MODEL OF 1918_ (_SCHNEIDER_)

_BREECH MECHANISM ASSEMBLY_]

=The breech mechanism= is of the plastic obturator, interrupted screw
type having four plain sectors and four threaded sectors. The block
can be loaded with one-eighth of a turn. Two of the plain sectors are
relieved to permit the breechblock to enter the breech recess. The
breechblock is screwed into the block carrier and rides on the hub of
the latter.

_The block carrier_ is hinged to the right side of the jacket by means
of the pintle hinge of the operating lever.

_The pintle hinge_ is fitted at the lower end with an operating lever
collar and detent. The dead weight of the breech is carried by the
block carrier hinge plate.

_The block_ is rotated by means of a rack which engages teeth cut in
the upper surface of the block at its rear end. The rack is actuated by
a lug on the under side of the operating lever which engages a slot in
the rack. The rack is located in the inside face of the block carrier.
When the breech is tightly closed this lock bears against the breech
face of the howitzer and is forced back against the rack lock spring
leaving the rack free to move. As the breech starts to open the rack
lock is forced up by its spring and locks the rack, preventing further
rotary motion of the breechblock.

_The operating lever_ is provided with an operating lever handle which
is kept in its raised position by the operating lever handle spring.
When the breech is closed and locked the lower portion of the operating
lever handle engages the block carrier lever catch. When the breech
is fully open the operating lever latch which extends through the
operating lever, engages the operating lever catch and holds the breech
in that position.

[Illustration: _155-MM HOWITZER MODEL OF 1918_ (_SCHNEIDER_)

_FIRING MECHANISM_]

_The obturator spindle_ is of the _mushroom head type_. It passes
through the center of the breechblock and is screwed into the front
end of the firing mechanism housing, which fits into the hub of the
block carrier. The obturator spindle is prevented from turning by the
firing mechanism housing key spring. A vent for the passage of the
primer flame is drilled through the center of the obturator spindle.
The obturator spindle bushing is screwed into the front end of the
obturator spindle and the obturator spindle plug into the rear end—the
latter forming a chamber for the primer.

The obturator spindle spring bears against the firing mechanism housing
and the breechblock, keeping the head of the obturator spindle tightly
against the _gas check pad_. The gas check pad or plastic obturator is
composed of a mixture of one part asbestos and three parts nonfluid
oil, contained in a canvas covering. The pad is protected by the front,
rear and small split rings. A steel filling-in disk is placed between
the gas check pad and the breechblock.

=The firing mechanism= housing is provided with a firing mechanism
safety plunger which is forced by the firing mechanism safety plunger
spring against the inside circumference of a circular boss on the face
of the breechblock. When the breechblock is rotated to its locked
position, the plunger slips into a notch in the boss and permits the
entrance of the firing mechanism block. When the breech is unlocked
the lower end of the firing mechanism safety plunger extends into the
firing mechanism housing and obstructs the entrance of the firing
mechanism block. This safety device makes it impossible to unlock the
breech while the firing mechanism block is in place or to insert the
firing mechanism block while the breech is unlocked.

The firing mechanism block is provided with a handle, and screws into
the firing mechanism housing. The primer seat plug is screwed into the
front end of the firing mechanism block and is provided with a notch
into which the primer is inserted. The firing pin guide is located
just back of the primer seat plug and forms a guide for the firing
pin as well as a bearing for the firing pin spring. The firing pin
housing is screwed into the rear end of the firing mechanism block
and held in place by the firing pin housing holding screw. The firing
pin passes through the firing pin housing and the firing pin guide and
is forced to the rear by the firing pin spring. The firing mechanism
block is provided with a flange at its outer edge in which a slot is
cut to receive a projection on the front of the percussion hammer.
This prevents the hammer from striking the firing pin when the firing
mechanism block is not screwed home. The firing mechanism block latch
is located on the outer face of the block carrier and prevents the
firing mechanism block from being unscrewed accidentally.

The firing mechanism block is interchangeable with the firing mechanism
blocks used on the following cannon:

155-mm. gun, model of 1918 (Filloux).

8-inch howitzer, model of 1917 (Vickers Mark VI and VIII½).

240-mm. howitzer, model of 1918 (Schneider).

=The percussion hammer= is carried by the percussion hammer operating
shaft which is journaled in the percussion hammer operating shaft
housing. This housing is secured to the breech face by means of a
dove tail projection which fits into a slot, cut across the entire
breech face just below the breech opening. The percussion hammer
operating shaft is fitted with a lever at its right end which receives
the blow of the firing mechanism striker when the lanyard is pulled.
The percussion hammer shaft plunger and spring are located in the
percussion hammer operating shaft housing to the left of the hammer.
When the breech is open the plunger is forced up by its spring,
thereby causing a projection on the plunger to engage in a recess in
the operating shaft, locking the shaft so that the hammer cannot be
operated. When the breech is closed the underside of the block carrier
strikes on the beveled head of the shaft plunger, forcing it down and
thus unlocking the mechanism.

The percussion hammer lock bolt is screwed to the face of the carrier
to the left of the percussion hammer. Its function is to lock the
hammer in the traveling position when the howitzer is not in use.

=Operation of the Breech Mechanism.= When the breech is closed and
locked, the threaded portions of the breechblock mesh with the threads
in the breech recess. The operating lever is held by the lower end of
the operating lever handle which engages the block carrier lever catch,
thus preventing any rotary motion of the breechblock at the instant of
firing. The firing pin receives the blow of the percussion hammer and
fires the primer. The flame passes through the vent in the obturator
spindle, igniting the propelling charge. The gas pressure in the bore
forces the mushroom head of the obturator spindle hard against the gas
check pad causing the latter to expand and press against the walls
of the chamber, forming a gas-tight joint. After the explosion the
elasticity of the pad causes it to resume its former shape, allowing
the obturator to be withdrawn freely from its seat when the breech is
unlocked.

=To Open the Breech.= After the piece has been fired, and before
unlocking the breech, press back the firing mechanism block safety
latch, screw out the firing mechanism block and remove the used
primer. The breech can not be unlocked with the firing mechanism block
in place. An attempt to do so will result in jamming of the firing
mechanism safety plunger. It is therefore important that the firing
mechanism block should be removed before attempting to unlock the
breech.

Press down on the handle of the operating lever in order to disengage
it from the block carrier lever catch. Move the lever toward the
rear and then to the right. In the first part of this movement, the
operating lever turns freely around the hinge pin and its lug operates
the rack which turns the breechblock. The threaded parts of the
breechblock are thus disengaged from the threads in the breech recess.
As the rack reaches the limit of its travel, the block carrier is swung
on its hinge drawing the breechblock out of the breech recess. As the
block carrier leaves the breech face of the howitzer the rack lock is
forced by its spring into the recess in the rack preventing any further
rotary motion of the breechblock in either direction. As the breech
reaches its full open position the right end of the operating lever
catch engages the operating lever catch, locking the breech in open
position.

In loading, care should be taken to ram the projectile home and to
enter the propelling charge in such a way that the igniter of the base
charge will be in contact with the mushroom head of the obturator
spindle when the breech is closed.

=To Close the Breech.= Press down on the operating lever handle to
disengage the operating lever latch from the operating lever catch and
move the operating lever to the left and forward. As the block carrier
comes in contact with the breech face of the howitzer, the rack lock is
pushed back into its seat, freeing the rack. Further movement of the
operating lever forces the rack to the left, rotating the breechblock
until its threaded portions mesh with the threads in the breech recess.
At the end of the movement of the operating lever, the operating lever
handle engages the block carrier lever catch and fastens the breech in
locked position.

Insert a new primer in the primer seat plug and replace the firing
mechanism block. The firing mechanism block can not be entered until
the breech is closed and locked. Any attempt to do so may cause damage
to the firing mechanism safety plunger or some part of the firing
mechanism.


THE CARRIAGE.

For the purpose of description, the carriage is considered as composed
of the following groups: _Sleigh (including recoil mechanism), cradle,
trail, traveling lock, elevating mechanism, traversing mechanism,
wheels, road brake, and shield_.

=The sleigh= contains the recoil and counter-recoil mechanism and
serves as a support for the howitzer, being secured to it by the breech
key and the holding-down band. The recoil counter-recoil cylinders,
and two air cylinders are bored in the sleigh and form the recoil
mechanism. The ends of the recoil and counter-recoil cylinders are
attached to the cradle and when the howitzer is fired the sleigh and
howitzer recoil, sliding on the cradle sides.

The holding down band is anchored on either side to the front band
clips, which are secured to the sleigh. Grooves are cut underneath the
two top edges of the sleigh, and are lined with bronze liners, known
as sleigh slides. These liners slide on the cradle clips and guide the
howitzer during recoil. Five longitudinal cylinders are bored in the
sleigh, the two upper cylinders running about one-third the length of
the sleigh, forming air tanks and are closed at the front end by the
air tank heads. The left air tank head is provided with an opening in
which the gage-cock body is assembled. A pressure gage may be assembled
through an adapter to this gage-cock for ascertaining the pressure
in the counter recoil system. The gage-cock is also provided with a
pointer which registers the quantity of liquid in the system on a scale
provided on the air tank head. =The two lower cylinders extending the
full length of the sleigh, form a housing for the recoil mechanism,
the right cylinder being the counter-recoil cylinder and the left the
recoil cylinder.= The small equalizing cylinder in the center of the
sleigh, extending only a short distance, is closed at the front end
with the filling valve, through which air or liquid is introduced into
the system.

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

SECTION, IN BATTERY]

=The counter recoil cylinder= is connected by a passage to the right
air tank and also to the small equalizing cylinder, the latter
being connected to the left air cylinder, thus maintaining equal
pressure in both air cylinders and in the counter-recoil cylinder.
The counter-recoil cylinder is closed at the rear end with the
counter-recoil cylinder head and at the front end with the stuffing
box, through which the counter-recoil rod and its piston moves. =The
recoil cylinder= is closed at the rear end with the recoil cylinder
head and at the front end with the recoil cylinder stuffing box,
through which the recoil piston rod operates. This rod is hollow and
serves as a buffer chamber for the buffer rod, which is securely
screwed to the recoil cylinder head at one end, the other end carrying
the counter-recoil valve. The recoil and counter-recoil rods are fitted
with the piston rod nuts on the front end which engage the piston rod
lock plate.

=The cradle= is a steel U-shaped plate reinforced by several transoms
and supported by the trunnion bracket, elevating segment brackets, and
in traveling position by the cradle band which engages the clips on
which the howitzer recoils when in action. The sleigh traveling locks
are mounted at the extreme ends of the cradle and used to lock the
sleigh to cradle when the howitzer is in traveling position.

The cradle is mounted on trunnions on the carriage, and by means of
elevating segments geared with the elevating mechanism may be inclined
at various firing angles. When carriage is traveling the rear end of
the cradle rests on the cradle traveling lock, thereby relieving the
elevating mechanism of the weight of the howitzer, sleigh and cradle.

The left trunnion of the cradle is bored out to receive the sight and
bracket. The shoulder guard is located on left side of the cradle just
back of the trunnion bracket and protects the gunner from the recoiling
parts. The firing mechanism is located on the right side of the cradle
and provided with a safety device which prevents the piece from being
fired when the piston rod nuts are not engaged by piston lock.

The recoil indicator is located just back of the trunnion bracket on
the right side of the cradle and consists of a steel spring which is
adjusted by means of a nut so that the pointer bears against a scale
engraved on the edge of the sleigh indicating the length of recoil. The
front end of the cradle is covered by the cradle head and provided with
an opening through which the pressure-gauge adapter may be assembled to
the gauge-cock body. The lower half of the front end of the cradle is
closed by the front transom, forming a guide for the piston-rod lock
which is operated by means of a lever. When this lever is lowered the
lock plate moves to the right, releasing the piston-rod nuts. When the
lever is raised the lock moves to the left, locking the nuts in firing
position. The locking device is protected by the cradle front cover
which holds the lever in firing position when closed. The filling valve
is accessible through the cradle bottom cover located on the bottom
of the cradle to the rear of the front transom. The pump bracket is
located on the left side of the cradle near the front.

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

LEFT SIDE ELEVATION, IN BATTERY]

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

ELEVATING MECHANISM]

=Recoil and Counter-Recoil Mechanisms.= When the howitzer is fired the
recoil mechanism exercises its retarding influence by means of a liquid
which is obliged to pass through an orifice whose size diminishes as
the movement proceeds, thus checking the recoiling mass. The recoiling
movement of the gun actuates at the same time the counter-recoil
mechanism, which acts on the counter-recoil liquid and forces it into
two reservoirs, thus further compressing a gas therein contained.
When the recoil movement is ended the expansion of gas forces the
counter-recoil mechanism back “into battery,” and the recoil
cylinder again exercises its retarding influence to prevent a too rapid
return and shock. The normal recoil is 51.375 inches (1.305 meters).

When the piece is fired the howitzer and sleigh move to the rear, the
recoil and counter-recoil rods, which are held by the piston-rod lock
remaining stationary. The liquid in the counter-recoil cylinder is
thus forced into the air cylinders, building up a pressure sufficient
to return the howitzer to battery. The liquid in the recoil cylinder
is forced through the orifices in the recoil piston rod and then
through the throttling ring. The tapered buffer rod, which is attached
to the recoil cylinder head, moves through the throttling ring,
gradually closing the orifice, thus keeping the pressure constant as
the velocity of recoil is reduced. As the buffer rod moves to the rear
the counter-recoil valve is opened, allowing the liquid to pass freely
into the buffer chamber. As the gun returns to battery the buffer valve
closes, forcing the liquid to pass through the small clearance around
the valve, thus absorbing the energy of counter recoil.

By means of the =elevating mechanism= the howitzer, sleigh and cradle
are inclined at the various firing angles, varying from zero to 42
degrees, by rotation in the trunnions of the cradle.

Two elevating segments attached to the cradle are actuated by the
elevating pinion shaft operating in bearings integral with the
elevating worm wheel case secured to trail. To lower end of worm shaft
is fitted a worm which engages a worm wheel and pinion shaft in the
gear case. On upper end of worm shaft is attached the elevating hand
wheel fitted with a handle and plunger enabling the operator to lock
the howitzer at any desired elevation. The motion of the handwheel is
transmitted through the worm gear to the pinion shaft and thence to the
elevating segments.

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

TRAVERSING ROLLERS]

The handwheel is provided with a handle of a spring locking type,
downward pressure on which unlocks it from the handwheel latch plate,
permitting the mechanism to be operated.

=Traversing Mechanism.= The traverse of the carriage is obtained by
means of the traversing mechanism causing the carriage to slide on the
axle, the trail pivoting on the spade. The movement is 3 degrees each
side of center or a total of 105 mils.

At the center of the axle is rigidly attached a bronze traversing nut
through which passes the traversing screw which may be operated from
either side of the carriage by means of handwheels connected to the
screw through bevel gears and shaft. The traversing screw operates in
the travelling housing longitudinally and held in position by thrust
bearings and thrust bearing adjusters at both ends of the screw. When
either of the handwheels is operated the traversing screw is rotated
and moves to the right or left as the case may be, carrying the entire
carriage which moves across the axle on traversing rollers.

In order to reduce friction during the traversing operation the
carriage rests on the axle through Belleville springs and two concave
faced traversing rollers mounted on roller shafts in the axle housing.
When gun is fired the Belleville springs are compressed and the
carriage rests on the axle through the bronze traversing roller boxes.

On top of axle projecting to the left of carriage is riveted an azimuth
scale graduated in mils so that the position of the carriage on the
axle may easily be seen at any time. When in traveling position the
carriage should be locked to the axles by the axle traveling lock, thus
relieving the traversing mechanism from unnecessary stress.

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

TRAVERSING MECHANISM]

The =axle traveling lock= is a device employed to relieve the
traversing mechanism from unnecessary stress when the carriage is in
traveling position. When the carriage is prepared for traveling the
traveling lock engages a series of square grooves cut in the center
of the axle. The lock is operated by an eccentric on the end of the
traveling lock shaft which is controlled by the lock lever fixed on
outer end. The lock lever may be placed in two positions marked “to
travel” and “to fire,” by means of its handle which is provided with a
spring plunger engaging the traveling lock catch. In order to properly
lock the carriage in traveling position it is necessary to traverse
the carriage to the center position on the axle, thus permitting the
locking device to engage the grooves cut in the center of the axle.

=The air pump= is furnished for the purpose of charging and maintaining
the necessary pressure in the counter recoil reservoirs. When in
operation it is attached to a bracket on the carriage by means of a
screw clamp and connected to the reservoir by the filling pipe. The
pump will operate against a pressure of 400 to 600 pounds per square
inch.

=The liquid pump= is a single-acting-plunger used for charging the
counter-recoil system and for the purpose of replenishing losses of
liquid from the cylinders. Power is applied through a hand lever
connected by parallel links and a cross-beam at the lower end of the
piston. The hand lever is detachable and also used in connection with
the air pump. When in operation the pump is attached to a bracket on
the carriage by means of a screw clamp. The filling pipe is employed to
connect the liquid pump with the recuperator cylinder.

=The reservoir for compressed gas= is a commercial seamless cylinder
with a capacity of 2,842 cubic inches and is charged with nitrogen gas
at a working pressure of 2,000 pounds per square inch (140 kilograms
per square centimeter). The reservoir is provided with a needle valve
and a connection for the pressure gage or filling pipe. This cylinder
is used for charging the counter-recoil system and may be carried on
the artillery supply truck furnished with 155-mm organizations.

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

AIR AND LIQUID PUMPS]

[Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER)

TRAVELING POSITION]

=The filling pipe= is used to connect the counter-recoil reservoirs
with the air or liquid pump or with the compressed gas reservoir.

=Pressure Gage.= The gage for the compressed gas reservoir is
calibrated from 0 to 150 kilograms per square centimeter. It is used
to ascertain the pressure of gas in the reservoir and must be attached
before screwing on the filling pipe. The gage for the pressure-gage
adapter is calibrated from 0 to 60 kilograms per square centimeter, is
screwed into the side of the adapter and used to test the pressure in
the counter-recoil system.

=The quadrant sight, model of 1918= (=Schneider=), is mounted on the
left trunnion of the carriage, both in traveling and in action, and
should not be removed by the battery mechanics. The principal features
of the quadrant sight are: The cross-leveling mechanism, the elevating
mechanism, and the angle of site mechanism.

_The cross-leveling mechanism_ principally consists of the leveling
worm, leveling stop, antibacklash spring, leveling clamp, and cross
levels. By means of the cross-leveling mechanism the quadrant sight is
adjusted to proper alignment with the bore of the howitzer.

_The bracket_ fits into the trunnion on the left side of the carriage
and is provided with four tennons which engage slots in the face of
the trunnions keeping the sight in proper alignment with the bore of
the howitzer. The bracket is screwed in place by the bracket bolt; the
front end of the body of the quadrant sight fits into the cylindrical
part of the bracket and is held in place longitudinally by four lugs.

[Illustration: _QUADRANT SIGHT, MODEL OF 1918._

(_SCHNEIDER_)]

The body of the sight is rotated by the _leveling worm_ engaging the
worm segment cut on the under side of the body. The outer end of the
worm is provided with a knurled hand wheel by means of which the
leveling mechanism is operated. The leveling stop, secured to bracket,
engages slot in the body, thus limiting the angular motion of the
body in either direction. The rear end of the cylindrical part of the
bracket is split and provided with a leveling clamp by means of which
the body may be locked in position after it has been leveled.

_The cross level_ is located on the rear edge of the sight shank and
serves the gunner in determining the level position of the instrument.
The level vial is a glass tube, closed at both ends, and partially
filled with a liquid consisting of 4 per cent alcohol and 60 per cent
ether, a small bubble remaining in the tube. Graduations are etched on
the circumference of the tube to indicate the central position of the
bubble. The vial is held in a level-vial tube, the ends being wrapped
in paper and set in plaster of paris. The knurled cross-level cover
fits over the holder and, together with the level-vial tube, are held
in place by the cross-level caps, which close the ends of the holder.
When closed, the cover serves as a protection for the vial.

_The elevating mechanism_ consists principally of a sight shank,
elevating worm wheel, antibacklash pinion, elevating worm, elevating
worm eccentric, elevating scale drum, and scale drum housing.


NOTES ON CARE OF THE 155 HOWITZER.

The executive should be perfectly familiar with the working of the
recoil and know when to put a gun out of action due to faulty recoil.
_The length of the recoil should be such that the end of the gun slides
do not recoil over the end of the cradle rails._ In counter-recoil,
the sleigh should be perceptibly slowed down at a point about 10
centimeters from the front of the cradle, and from there on should
ease gently into battery without a sound or shock. Strict watch
should be kept to see that no excessive leakage takes place through
the stuffing boxes, the valve in the gauge adapter, or the oil hole in
the cylinder end nut. Slight leakage can hardly be helped, as one of
the stuffing boxes is under more than four hundred pounds of pressure
per square inch when the gun is at rest, and three or four times that
amount when the gun is in full recoil. However, if a pool of liquid
is found after the gun has been standing all night, it is time to
report the matter and have the packings replaced. The gun must be
dismounted, the stuffing-box repacked, and the dermatine inspected.
The dermatine packing is a compound resembling rubber, but it has the
quality of resisting any chemical action that the liquid may set up
in the recuperator. A worn dermatine packing may be replaced by the
simple expedient of turning it wrong side out and then using it again
as before. This has actually been tried and found to give good results.
Another temporary repair was effected by cutting a ring from a solid
truck tire and using it in the place of the dermatine, until a packing
of the latter could be obtained.

The French obtain a very tight fit in their stuffing boxes by the
peculiar design that allows the liquid pressure to actuate a strong
spring which in turn expands the packing against the rod or cylinder
wall. Leakage through the recuperator stuffing box will be noticed by
the liquid coming out of the oil hole in the right-hand cylinder end
nut.

In dismounting French materiel, care must be used to replace the
same nuts on the bolts from which they were taken. Threads are not
standardized as to diameter; hence, trouble is likely to occur when
remounting.

=To dismount the tube from the recoil mechanism, or sleigh= as it is
denoted, a suitably strong overhead beam is selected and the carriage
run beneath it. Mount two one-ton duplex blocks on the beam over either
end of the tube and thread the bore with a half-inch wire cable sling,
in such a manner as to leave a bight at both muzzle and breech ends.
Into these loops the hooks of the block catch. Gunny sacks form a
suitable packing at the muzzle and breech to prevent the cable damaging
these parts of the tube. Provide several blocks of two by four or four
by four stuff, to block up the sleigh as it is moved to the rear—as
we shall soon see that it does. Remove the locking hoop by knocking
out the retaining bolts, and also remove the cradle bolts from their
housing on the cradle. This will allow the sleigh to move to the rear
of the cradle. Take a strain on the blocks and carefully move the
sleigh back over the trail until the recoil-lug key (locking the recoil
lug to the sleigh) clears the end of the cradle. Remove the set screw
from the bottom of the sleigh which locks the tapered key in place,
and proceed to drive the key out with a sledge hammer and a block of
wood. During this operation the rear of the sleigh must be blocked up
on the trail in order to take the strain off the cradle rails. After
the key is cleared, the tube may be raised by means of the two blocks,
care being taken to make the lift vertical, otherwise the slots and
grooves just in front of the breech will jam and be damaged. Remove the
carriage and lower the tube onto blocks. The process of mounting is
just the reverse of the above.

The elevating and traversing mechanisms give little trouble, if all
gear cases are kept packed in grease. It is extremely important that,
in laying for elevation with this piece, the final turns of the
handwheel should bring the gun into correct position by raising the
breech and not by lowering it. In this way all backlash is taken out of
the gearing and the howitzer rests solidly for firing. The gunner may
easily be taught to remember this by always having him bring the range
bubble to the front of the glass and then slowly elevate the breech,
bringing the bubble to him.

The traversing mechanism moves the whole carriage, including gun, along
the axle, about the spade as the center of rotation. The traversing
screw moves the carriage by being rotated through nut set solidly in
the axle. The axle and nut are stationary and the screw moves laterally
by means of the traversing handwheel. Hence, the carriage being
attached to the screw, must move when the screw moves. Inasmuch as the
axle is straight, it must accommodate itself to the arc of the circle
described about the spade as the center. It does so by moving tangent
to the arc, and consequently one end moves to the front and the other
end moves to the rear, carrying the wheels with them. From this it will
be seen that before attempting to traverse the piece, the brake must be
“off.” The movement of the wheels may be easily seen, if a pencil line
be drawn across the tire just above the brake shoe and then the piece
traversed. The line will be seen either to raise or lower according to
whether the piece be traversed to the right or left.

In filling the “brake” or recoil cylinder, good results have been
obtained by merely leveling the gun and filling the brake cylinder
until full. Trying to pour out one hundred cubic centimeters of the
liquid after the brake is full, as the French drill regulations
lay down, is almost impossible; and no bad effects will be noticed
provided the gun does not become excessively warm during the firing.
If it should become warmed up sufficiently to affect the recoil,
level the gun, unscrew filling plug to release the pressure, rescrew,
and continue the fire. In using the manometer gauge, to measure the
pressure and the height of the liquid in the recuperator, it will be
found that the valve in gauge adapter will sometimes stick open to
the extent of letting out all the air in the recuperator tanks. The
only sure remedy for this is entirely to dismount the gun, remove the
adapter, and replace its valve packing, which no doubt will be found to
be worn and frayed, or else some foreign substance will be found to be
lying between it and its seat. The gauges should be tested about once
in three months by means of a standard steam gauge testing apparatus,
making the appropriate transformations if the tester be graduated to
pounds per square inch as most steam testers are. It will be found that
the maximum steam pressures used are rather lower than these gauges
read, hence only the lower readings may ordinarily be tested.

To set the pointer to the correct pressure reading, pull the pointer
loose and apply a known pressure to the gauge. Set the pointer at the
corresponding reading on the manometer and press it on tightly. In
general, this is sufficient for practical work.

After each firing the breechblock should be entirely dismounted and
each part washed in caustic soda solution and then stippled with oil
before reassembling.

The wheels are made of smaller members than those that we are
accustomed to see in our own materiel. It must be remembered, however,
that the French designed their wheels for much better roads than ours;
and, in comparison with our materiel throughout, this fact must be
borne in mind. The wheels must be carefully watched, especially through
the dry weather, for they tend to check and crack. Remedies are tire
shrinking and soaking in water over night, followed by a thorough and
careful application of linseed oil. Fast travel, as when the piece is
coupled to a truck, must be avoided if the life of the carriage is to
be assured.

According to the French drill of the gun squads, in going into action,
the piece is first unlimbered and the trail is then laid on the ground,
and the cannoneers change posts to the extent of the gunner going to
his position by his sight; while the remaining cannoneers lift the
trail again and set the spade. This is slow and cumbersome work. Much
better results may be obtained by setting the spade at the time that
the piece is unlimbered, without moving the cannoneers from their
posts.




CHAPTER XII

EXPLOSIVES, AMMUNITION AND FUSES.


EXPLOSIVES.

As a matter of practical interest, explosives may be divided into three
classes, namely:

(1) Progressive or =propelling explosives= called =low explosives=.

(2) Detonating or =disruptive explosives=, termed =high explosives=.

(3) =Detonators= or exploders, known as =fulminates=.

The first includes all classes of gun powders used in firearms of
all kinds; the second, explosives used in shell, torpedoes, and for
demolitions; the third, those explosives used to originate explosive
reactions in the two first classes. Corresponding names are given
to the phenomena characteristic of each class of explosives, (1)
explosions proper, of low order, progressive, or combustions, (2)
detonations, of high order, (3) fulminations, this last possessing
exceptional brusqueness.

The explosion of low order is marked by more or less progression; the
time element is involved as a controlling factor, the time required to
complete the explosive reaction being large compared with that of the
other forms of explosion.

The second class of explosion is of a different nature. The explosive
reaction is not limited or confined to the surfaces exposed but appears
to progress in all directions throughout the mass radially from the
point of initial explosion. It has been determined experimentally that
the velocity of propagation of the explosive wave throughout a mass of
guncotton is from 17,000 to 21,000 feet per second.

Fulmination is a class of explosion still more brusque than the
last. The abruptness of their explosion and the consequent sharpness
of the blow and the concentration of heat on the point of ignition
constituting their efficiency as originators of explosions of the first
two classes.

=Methods of Exploding.= Explosives may be exploded by three methods; in
reality but two, by heat and by application of energy as by a blow. The
heat may be applied directly by friction, by electricity and detonating
cap, these two methods of applying the heat giving rise to the three
practical methods above mentioned. As it is not practical to apply heat
directly to the charge, small charges of special explosives are made up
into primers and these are exploded in one of the ways above mentioned
and so communicate the explosion to the main charge. Fulminate of
mercury is one of the high explosives fulfilling the requirements and
it is readily exploded by any one of the methods mentioned. It is used
in all detonating caps. Primers for cannon also contain an additional
charge of black powder to increase the flame. For this purpose also
igniting charges of black powder are attached to the smokeless powder
charges for the larger calibers.

=Uses.= The chief use of low or progressive explosives is as a
propelling charge in guns and for blasting where it is desired to exert
a pushing effect rather than a blow. High explosives are used when it
is desired to exert a high pressure and shatter the container, as in
a shell, mine, etc. This class is not satisfactory as a propelling
charge for the reason that its rapidity of action is so great that
the pressure exerted would burst the gun before the projectile could
start. Low explosives are not satisfactory shell fillers for the reason
that their action is so low that the shell would break at its weakest
point before all the explosives had exploded and what remained would
be wasted. With a high explosive, all or most of the charge explodes
before the shell can break up. The greater the rapidity of action of an
explosive the finer the fragmentation of the projectile. With too rapid
action the pieces are too small; with too slow action they are too
large. Experience teaches the proper rapidity of action to attain the
fragmentation most efficient against animate and material targets.

=Propelling Charges.= Up to the present time nitrocellulose powder has
complied better with the requirements of a suitable, smokeless powder
than any other that has been proposed and is used in our service for
propelling charges in guns. The danger of manufacture is also less than
that of nitroglycerine powders. Moreover the latter, which was formerly
used in our service and still is in the British and some others, causes
too much erosion of the tubes due to the greater heat of explosion. It
has the advantage of requiring a smaller charge for the same muzzle
velocity and therefore a smaller powder space and consequent lighter
weight of gun.

=Shell Fillers.= High explosives for shell fillers. Up to the present
explosive “D,” trinitrotoluol and picric acid are the principal high
explosives which fulfill the requirements as shell fillers. Explosive
“D” on account of its great insensitiveness to shock is used in armor
piercing projectiles and also in field gun and howitzer shell. It is
detonated by a fuze. Trinitrotoluol is used in submarine mines and in
general demolition work as it is much easier to explode than explosive
“D.”

=Table of Explosives.= The following table gives a good idea of the
principal explosives in use in our service and the characteristics of
each:

                                 High
            Purpose.            or Low.               Name.
  Propelling charge in guns.        L     Nitrocellulose, smokeless
                                            powder.
  Bursting charge, projectiles.     H     Picric acid, explosive “D”
                                            (powder form)
                                            Trinitrotoluol.
  Blank, saluting charges.          L     Black Powder.
  Re-inforce charges, primers.      L     Black Powder.
  Base charge, shrapnel.            L     Black Powder.
  Time trains, fuzes.               L     Black Powder.
  Igniting charges, cannon.         L     Black Powder.
  Charges, submarine mines.         H     Trinitrotoluol wet guncotton.
  Igniting elements, fuzes          H     Fulminate of mercury, chlorate
      and primers.                          of potash (potassium
                                            chlorate).

=High Explosives.= The principal high explosives used as shell fillers
in our service are: picric acid, explosive “D” and trinitrotoluol,
or more popularly known at TNT. The picric acid and picrates used as
shell fillers are secret compositions. Mellinite, essentially picric
acid alone or with some other substance is used as a shell filler by
the French. It is poured into the shell in a fused state and allowed
to harden, thus giving a very compact charge and one easily handled.
It has the disadvantage however of forming unstable compounds with
the metal of the shell and great care must be exercised in coating
the interior of the shell with a protective coat before pouring in
the fused mellinite. Lyddite is the English equivalent of mellinite.
Picric acid was also used by the Japanese or it may be a mixture of
picric acid and some nitro compound. The most successful explosive of
this type is explosive “D” invented by Colonel Dunn of our Ordnance
Department and sometimes known as “Dunnite.” It is not fusible and
must be compressed for use as a shell filler, being forced into the
shell by compression. This is a disadvantage as compared to mellinite
as the density of loading is less and weight for weight therefore less
efficient. It is little sensitive to shock and therefore not very
dangerous to load even under great pressure. Trinitrotoluol is also
used as a shell filler but its chief use is in demolition work and as
the charge for submarine mines.

=Nitrogen Compounds.= It may be interesting to note that all of the
principal explosives with which we have been dealing are compounds
containing nitrogen. In fact the war has been fought with fixed
nitrogen which explains the great interest taken in the various
attempts to fix the free nitrogen of the air which is the world’s great
storehouse of free nitrogen. As nitrogen is also a necessary ingredient
in the various fertilizers, the result to the world of a commercial
process for speeding up the cycle of changes through which nitrogen
passes in its life giving mission from free nitrogen in the air to its
various compounds in the nitrogeneous animal and vegetable tissues is
almost limitless and as usual war has been the incentive to speed up a
process which will result in incalculable value to mankind.

=Classification.= Guns are loaded with three kinds of ammunition:
fixed, semi-fixed and separate loading ammunition. In fixed ammunition
the round is complete and projectile and powder loaded into the chamber
at the same time. In semi-fixed the projectile is separate from the
powder charge, which however is put up and loaded into the chamber in a
container. In separate loading ammunition the powder is loaded into the
chamber in bags. In the first two cases the cartridge case furnishes
the means for sealing the rear of the powder chamber against escape to
the rear of the powder gases. In the last case some form of obturating
device is made a part of the breechblock furnishing a gas check to seal
the rear of the powder chamber.

=Fixed Ammunition.= All of our field guns below 5 inches in calibre use
fixed ammunition. The powder is placed loose in the cartridge case,
the space not filled with powder being stuffed with packing paper,
excelsior, or felt wadding next to the projectile so as to hold the
powder in contact with the primer, in some fixed ammunition a brass
diaphragm is soldered to the inside of the case for the same purpose
and to keep out moisture, (4.7” Gun). An igniting charge of black
powder is a part of the primer and in some cases an additional charge
is placed at the forward end of the powder space in the cartridge case
to insure rapid ignition of the smokeless powder. In this case it is
held in place between two quilted disks of crinoline.

=Semi-fixed ammunition= is employed in our 6” and 4.7” field howitzers.
The cartridge case contains three weights of propelling charge for
firing in the three zones designed to give a high angle of all with
these weapons. Access to the charge is had by tearing off the brass
diaphragm closing the forward end of the cartridge case. By removing
the first charge the remaining charge is that prescribed for the second
zone, and by removing the top two charges the remaining charge is that
of the first zone. The three charges are tied together and the middle
charge has an igniting charge of black powder attached. The removal of
charges is facilitated by the separate container for the powder charge
and the round is more easily handled in the two parts especially in the
case of the six-inch howitzer, where the projectile weighs 120 lbs.
The same primer is used as in fixed ammunition, the cartridge case
performing the function of an obturator.

[Illustration: BREECH MECHANISM OF 155 GUN SHOWING DE BANGE OBTURATOR.]

=Separate Ammunition.—Obturation.= The 155-mm Filloux gun and 155-mm
howitzer use separate ammunition. In such guns there must be provided
some form of a gas check which will prevent the powder gases from
rushing to the rear into the threaded portion of the breechblock, as
this would soon erode the thread sectors and render the gun useless
beside losing a large amount of pressure in the bore. The device
used as a gas check is called an obturator. There are two systems of
obturation in use, named after their inventors:

The DeBange and the Freyre. The former is used in the 155’s. It
consists of a steel mushroom head closing the rear of the powder
chamber, the spindle of which passes through a central hole in the
breechblock. Between the mushroom head and the face of the breechblock
is a pad of asbestos, paraffine and tallow, pressed into shape by a
hydraulic press and covered by canvas or asbestos wirecloth. Split
rings having hardened outer surfaces are fitted, one just behind the
mushroom head and one just in front of the face of the breechblock.
Their diameter is slightly greater in the free state than the conical
surface of the bore where they bear when the breech is closed so that
they always close the rear of the powder chamber. The pressure of the
powder gases forces the mushroom head to the rear and this compresses
the asbestos pad which in turn forces the split rings to bear with
greater force against the walls of the powder chamber thus securely
closing the rear opening of the powder chamber. For more details of
this device see pages 302 to 306 Tschappat’s O & G.

=Powder Bags.= Cartridge bags for separate loading are made of raw
silk, and are sewed with silk thread. Other materials are apt to
produce flare-backs or premature explosions because they are not
entirely consumed in the bore or continue to burn if not consumed.
The raw silk however either is entirely consumed or if not, the parts
ignited immediately go out as soon as the flame is removed and do not
smoulder. Specially treated cotton fibre bags have been tried but so
far as I know have not as yet superseded the raw silk for the purpose.
The gases remaining in the bore after the discharge of a charge of
smokeless powder are explosive and with air form an explosive mixture,
hence the danger upon opening the breech if any smouldering particles
remain in the bore.

[Illustration: _21 GRAIN PERCUSSION PRIMER MARK II-A_]

=Primers.= The devices for initiating explosions of propelling charges
in military guns are called primers. With fixed and semi-fixed
ammunition the primers are seated in the base of the cartridge case.
In the case of separate loading ammunition the primers are inserted
separately in the breechblock, the expanding gases of the detonated
primer forcing the walls of the primer case tightly against the bore
through the breechblock and thus sealing this channel of escape for
the gases from the powder chamber. This necessitates a much larger and
stronger case for separate loading primers than for those inserted in
the base of a cartridge case.

=Classes of primers.= Primers are divided into three classes according
to the method by which they are fired: (a) _friction primers_, (2)
_electric primers_, (3) _percussion primers_. Combination primers are
made which may be fired by any two of these methods, usually electric
and one of the others. The characteristics of a good primer are,
certainty of action, safety in handling, no deterioration in storage,
simplicity in construction and be cheap to manufacture. They are also
divided into obturating and non-obturating depending upon whether they
close the vent during discharge or not.

=Primer pressing.= Primers for fixed ammunition are inserted in the
base of the cartridge cases by means of a special press for this
purpose. The primer body is a trifle larger than the seat in the
cartridge case provided. This seat is rough bored to a diameter less
than the finished size and then mandreled to finished dimensions with
a steel tapered plug. This process toughens the material of the case
around the primer seat and prevents the expansion of the primer seat
under pressure of the expanding gases.

=Percussion primers.= Except for very heavy siege guns and railroad
artillery the guns handled by the Field Artillery use percussion
primers. The 110-grain percussion primer is the one in use in our
service and as typical will be described. The charge consisting of 110
grains of compressed black powder makes the charge burn like a torch
rather than explode, which facilitates the ignition of the charge of
smokeless powder, with which the flame comes in contact. The diametral
holes spray the flame in several directions thus insuring ignition
at many points simultaneously. The percussion element consists of a
percussion primer cup, the percussion composition and an anvil, all of
which are assembled together in a cup in the rear face of the primer
case. The percussion composition is made up of chlorate of potash,
sulphide of antimony, ground glass and sulphur. A blow upon the cap by
the firing pin detonates the percussion composition and the flame from
this detonation ignites the black powder which in turn explodes the
charge of smokeless powder.


The General Shape and Nomenclature of Projectiles.

The reason for the particular shape of shells may not be clear to
all. In the first place all matter has the property known as inertia,
which we may define as that tendency of matter to remain in a state
of rest or to continue at a uniform velocity if in motion. It offers
a resistance to any change in the state of either rest or motion
whether of amount or direction. Consequently when we apply a sudden and
tremendous force to the base of a projectile by means of the expansive
force of exploding powder gases, there will be set up in the metal a
resistance to this force in which every particle of the projectile will
resist by an amount proportional to the mass of particles beyond the
point of application of the force to itself. The actual force will be
proportional to the weight and acceleration produced by the applied
force in the projectile. This explains the reason why the _walls of
the projectile are thicker near the base_. It also explains the method
of calculating the thickness of walls, for if we know the weight at
any cross section and the co-efficient of strength of the metal we may
calculate the thickness of walls necessary to withstand the pressure
for any given muzzle velocity which is fixed by other considerations.
It explains also the preference for steel in projectiles as for the
same weight the steel is much stronger making it possible to throw a
greater amount of shrapnel or high explosives in shell.

[Illustration: _155-MM COMMON STEEL SHELL MK IV_]

The necessity for compact loading, especially in the case of high
explosive shell is also noted as otherwise the shock due to inertia
would break up the charge and perhaps cause a premature explosion.
Hence it is very necessary to guard against airholes in filling shell
cavities.

In order to secure regular and uninterrupted movement of the projectile
through the bore it is necessary that the projectile and bore have
the same geometric axis. Also the projectile must be seated exactly
and uniformly for succeeding rounds in its seating in the bore. This
latter is necessary in order that the powder chamber may not vary as
this would give irregular pressures. The liability of _strapping the
rotating bands_ or setting off the fuze in certain kinds of fuzes are
also explained by inertia. It might even cause sufficient shock to
detonate the charge in the shell. The remedy is accurate seating of
each projectile by reason of trained gun crews using the same amount
of force at each ramming. The first condition, coincidence of axes, is
obtained by means of the ogival head which has a diameter some tenths
of a millimeter smaller than the diameter of the bore, and serves as a
front support for the projectile while the rotating bands center it in
rear. Were it not for the bell the projectile, held only by the soft
material of the rotating band, would wabble in its travel through the
bore and tumble soon after leaving it. It is also necessary that the
center of gravity of the projectile be on its geometric axis. Otherwise
it will travel on a spiral of the same pitch as the grooves and knock
the tube walls as it travels through the bore and without the support
of the bell might cause a premature explosion by actuating the fuze.

[Illustration: _155M/M SHRAPNEL—95 LBS.—MARK-I._]

[Illustration: COMMON STEEL SHELL MARK I.

COMMON STEEL SHELL MODEL OF 1905.

SHRAPNEL.

CARTRIDGE CASE.

4.7” Gun Ammunition.]


Three-inch Ammunition.

=Fixed ammunition= is used in the 3” field guns, and is made up with
either common shrapnel, high explosive shrapnel, or common steel shell.
The rounds as made up vary in length with the type of projectile used.
The ammunition chests of the battery are of sufficient size to take
any one of the rounds furnished, so that the number of each kind to be
carried is a matter for regulation by proper authority. Each round is
issued with projectile filled and fused. The weight of the projectile
is 15 pounds, and the total weight of one round is 18.75 pounds. The
components of one round are _the cartridge case with primer, the powder
charge, igniter, projectile and fuze_.

=The cartridge case.=—The cartridge case is a solid drawn-brass case
10.8 inches long; it has a capacity of 66.5 cubic inches, and weighs,
with primer, 2.25 pounds. A circular groove is cut in the base of
the cartridge case and _the groove is painted red for high explosive
shrapnel, yellow for common shrapnel, and black for high explosive
shell_.

=The primer.=—The percussion primer, known as the “110-grain percussion
primer,” contains an igniting charge of 110 grains of black powder in
addition to the essential elements of a percussion primer. The purpose
of the black powder is to insure the ignition of the smokeless powder
charge in cartridge case.

[Illustration: _Common Steel Shell._

_Common Shrapnel._

_Cartridge Case._

_Semple Tracer._

_High Explosive Shrapnel._

3” AMMUNITION]

=The powder charge.=—The powder is a nitrocellulose powder composed
of multiperforated (7 perforations) cylindrical grains, each 0.35”
long and 0.195” in diameter. The charge varies slightly for different
lots of powder, but is approximately 24 ounces. The charge gives a
muzzle velocity for shrapnel of 1,700 feet per second (1600 f/s for
shell) with a maximum pressure in the bore not exceeding 33,000 pounds
per square inch. At the front end of the cartridge case there is an
igniter of black powder weighing about ¼ oz. which assists in the
uniform ignition of the smokeless powder charge.

=The projectiles.=—All projectiles have a copper rotating band 1.2”
from the base. This band engages in the rifling of the bore of the
piece, and gives the projectile a rapid rotation about its long axis
during flight. This causes it to travel straight, point on, without
tumbling.

=Common shrapnel.=—The common shrapnel is a base-charged shrapnel
fitted with a combination fuze. The case is of steel with solid base.
The shrapnel filling is composed of 252 balls, each approximately 167
grains in weight (42 to the pound). The balls are approximately 0.5” in
diameter. The balls are poured around a central tube and rest upon a
steel diaphragm, the interstices containing a smoke-producing matrix.
The bursting charge consisting of 2¾ oz. of black powder is in the
base and is covered by the diaphragm which supports the central tube,
affording a conduit to the flame leading from the fuze to the bursting
charge.

In action the case is not ruptured upon the explosion of the bursting
charge; the head is stripped and the balls are shot out of the case
with an increase of velocity of about 274 feet per second. The
remaining velocity of the shrapnel at 6,500 yards is approximately
724 feet per second and the time of flight 22 seconds, so that at
that extreme range, with the increase of velocity due to the bursting
charge, this shrapnel with 21-second fuze will be effective. The weight
of the shrapnel with fuze is 15 pounds.

Shrapnel is a projectile containing a great number of hardened steel
balls, each approximately ½” diameter, which may be projected from
a point in the air (called the _point of burst_) close to but short
of the target. Each ball is capable of killing a man or horse at
a distance up to 250 or 300 yards from the point of burst. Taken
collectively, the paths of these balls form a cone, called the _cone
of dispersion_. The ground section of this cone is elliptical in shape
with its longer axis approximately in the plane of fire. At mid-range
when burst at _normal height of burst_ (H. B. = 3 mils), the dimensions
of this area are approximately 20 yards wide by 250 yards deep. These
dimensions will however vary with the _angle of fall_, _the height
of burst_, the _slope of the ground_ at the target, and the relation
between the _linear_ and the _rotational velocities_ of the shrapnel at
instant of burst in the air. A 3-mil H. B. is chosen because this gives
an average density of 1 hit per square yard of vertical target area. An
infantry skirmisher (standing) with his interval occupies approximately
1 square yard.

Shrapnel has very little effect upon material objects. It is very
effective against personnel not protected by cover, or to search an
area which is known to be occupied, or which must be traversed, by
hostile troops.

_Ehrhardt High-explosive shrapnel._—The Ehrhardt high-explosive
shrapnel is fitted with a combination fuze and a high explosive head.
The case is drawn steel with solid base. The shrapnel filling is
composed of 285 balls, each approximately 138 grains in weight (50
to the pound). The balls are poured around the central tube and rest
upon the steel diaphragm, the interstices containing a matrix of high
explosive.

In time action (burst in air), the case is not ruptured upon the
explosion of the bursting charge, but the head is forced out and the
balls are shot out of the case with an increase of velocity of from 250
to 300 feet per second. In the meantime the head continues its flight,
detonating on impact.

If the fuze be set at “safety” or for a time greater than the actual
time of flight, this shrapnel may be used in lieu of high-explosive
shell. Upon impact a high-explosive shrapnel is detonated by means
of the percussion element of the combination fuze, the head being
detonated first, which detonation causes the sympathetic detonation of
high-explosive matrix surrounding the balls.

=Common steel shell.=—This steel shell is high-explosive and fitted
with a base detonating fuze. The case is hollow and made of drawn
steel. It is provided with an ogival head. The steel shell contains a
bursting charge of 13.12 ounces of Explosive D. The weight of the shell
with bursting charge and fuze is 15 pounds. The shell is always issued
filled and fuzed.

This shell bursts on impact and with great force exerted in all
directions. It is a powerful instrument for the destruction of material
objects such as guns, intrenchments, houses, stone walls, etc. The
effect, however, is very local.

=Frankford Arsenal combination fuzes.=—These fuzes are point fuzes with
combination time and percussion elements for use with common shrapnel.
They are of the type known as the ring or “dial” fuze, in which the
time train is set by turning a graduated ring which carries part of the
train. These fuzes may be reset as often as desired.

=Ehrhardt combination fuze for high explosive shrapnel.=—This fuze is
similar to the Frankford Arsenal Combination time and percussion fuze
but in addition contains a high explosive head and detonating element.
Due to this arrangement, both the projectile and the high explosive
head have a high-explosive shell effect when striking on impact.

=The service base detonating fuze.=—The details of the detonating fuze
and the composition of the detonator are kept secret. A detonating
fuze is necessary in order to produce a higher order of explosion by
causing an instantaneous conversion of the high explosive compound
called “Explosive D” with which the shell is charged. If an ordinary
percussion fuze were used only an ordinary explosion would be produced
as in the explosion of black powder.

=Preparation of blank metallic ammunition.=—Blank metallic ammunition
will always be assembled under the personal supervision of a
commissioned officer, who will be held responsible that it is prepared
in the manner prescribed. (G. O. 9, War Dept., Jan. 11, 1908.)

For this purpose there are issued blank-cartridge cases, black powder
in bulk, tight-fitting felt wads, rubberine, or other quick-drying
paint, primers, etc.

Before assembling, the cartridge cases should be carefully inspected to
see that they are in sound condition and thoroughly clean and dry. They
should also be tested by trying them in the gun, to determine whether
they have become deformed. Any cases that do not readily enter the
chamber in the gun or that are otherwise seriously deformed should be
laid aside for resizing. After inspecting the cartridge cases the blank
ammunition should be prepared as follows:

(a) Insert the primers with the primer-inserting press.

(b) Pour into the cartridge case the proper weight of black powder and
shake it down well.

(c) Insert the felt wad and press it down hard until it rests squarely
on the powder charge.

(d) Give the upper surface of the felt wad and the inside of the
cartridge case just above the wad a good coat of the rubberine or other
quick-drying paint furnished for the purpose, using a brush, and allow
the case to stand until this coat is dry. Then apply another coat of
rubberine paint in a similar manner. The object of using rubberine
paint, which is strongly adhesive, is to thoroughly seal the joint
between the wad and the case to prevent any powder grains from leaking
out, and at the same time to firmly hold the wad in place.

=The reloading and cleaning outfit.=—This outfit consists of the
following parts, and is furnished to each battery:

  Primer-inserting press, small
  Bushing
  Powder measure, saluting
  Decapping tool, with guide
  Cleaning brush
  Hammer
  Case holder
  Case-holder stand
  Storage chest

The bushing is used in the primer-inserting press for the insertion of
new primers.

The decapping tool and case holder and stand are used for removing
exploded primers from the cartridge cases. A light blow on the rod with
a piece of wood or the bronze hammer generally removes the primer.

A powder measure to suit the saluting charge for the gun is furnished,
and when level full holds the required charge.

The cleaning brush is furnished for cleaning the cartridge cases after
they have been used and should be ordered to suit the size of case for
which intended.

=Care of Cartridge Cases.=—As soon after firing as practicable the
exploded primers should be removed from the cartridge case by means
of the decapping tools furnished with the reloading outfit. The case
should then be thoroughly washed in a strong solution of soft soap and
soda to remove all powder residue. It should then be thoroughly dried.

If the cartridge cases are carefully cleaned and washed immediately
after firing, not only will less labor be required but the life of the
cartridge case will be greatly prolonged.

A good solution for washing cartridge cases may be prepared by using
ingredients in the following proportions: 1 gallon of water, 2½ ounces
of soft soap, 5½ ounces soda. The mixture should be boiled and stirred
until the ingredients are entirely dissolved.

In washing cartridge cases this solution should be used hot and in
sufficient quantity to completely immerse the cases.

Neither acids nor solutions of acids will be used for cleaning
cartridge cases.


Precautions to be Observed with Fixed Ammunition.

(a) Do not unnecessarily expose ammunition to the sun or load it into a
warm gun before time for firing; if this is done, erratic shooting will
result.

(b) Handle carefully, otherwise cartridges may become deformed and
cause jams.

(c) Never use force or any implements on the base of the cartridge in
loading.

(d) See that fuzes set at safety or are provided with waterproof brass
cover for transport.

(e) Do not fire ammunition which has been under water with the
waterproof brass cover removed.

(f) Both service and blank ammunition should never be carried in the
battery at the same time. If conditions are such that both may be used
in exercises, only one kind should be in the firing battery; the other
should be under lock and key outside the firing position.

(g) Misfires and hangfires are of exceedingly rare occurrence. In case
of a failure to fire, the firing handle should be pulled again in order
to snap the trigger. If this fails to fire, the breech should _not be
opened_ until after the expiration of at least one minute, when the
round or cartridge should be removed and placed to one side. Defective
ammunition, cartridges and primers should be reported.


With Blank Ammunition.

Firing with blank ammunition will be greatly facilitated by a careful
observance of the following:

(a) Before firing, a careful examination should be made of the
assembled rounds to see that the felt wads have not become displaced
or the cartridge cases dented or deformed by careless handling.
If the cartridge cases have been properly resized and are clean,
no difficulty should be experienced in inserting them in the gun,
provided the chamber of the latter is clean. The continued insertion of
cartridge cases that are not clean causes an accumulation in the gun
chamber which may make the insertion of subsequent rounds difficult or
impossible.

(b) In firing blank ammunition the gun chamber will be sponged after
each round with a damp sponge, to extinguish sparks and remove powder
residue resulting from the previous round, before the insertion of
another round.

(c) Care will be taken to see that the sponges are not worn and that
they thoroughly fit the chamber. The interval between rounds in firing
blank ammunition should be sufficient to allow thorough sponging of
the chamber and examination to ascertain that all sparks have been
extinguished.

(d) Wads for the preparation of blank metallic ammunition are made to
tightly fit in the cartridge case. No wads should be used that are not
a tight fit in the case.


FUZES.

=Principle of operation.=—We have just learned something of the force
of inertia in connection with a projectile. Most fuzes are actuated
by this force. From our knowledge of the trajectory we know that
usually a projectile does not strike on its nose. Therefore we cannot
devise our fuzes to work like the driving of a nail into a board. The
striking element is the anvil and is a fixed pointed spur against
which a sliding element containing a fulminate strikes. The sliding
block carries a small charge of black powder which is set off by the
fulminate, thus igniting the train which leads to the high explosive
charge detonator. Were this sliding block left free to slide back and
forth at all times it would be unsafe to transport the fuze, as it
might be set off by accident. There must be therefore some means of
holding it safely away from the anvil until it is desired to detonate
the charge. There are thus two conflicting conditions to be met: safety
during transportation and sensitiveness at the point of departure.
It may not be understood at first why sensitiveness at the point of
departure should be a condition to be met. Suffice it to say that all
fuzes are designed to arm at discharge or soon after leaving the bore
for they must be ready to act at any time after leaving the muzzle.
Were they to be safe during flight they might be so safe that the
remaining velocity would not be sufficient to set them off. All fuzes
are designed to arm as we say either during travel through the bore or
immediately after.


Methods of Arming.

_Spring method._—Let us suppose that after our projectile has started
on its way the sliding block is free to move within a cavity at the
forward end of which is the anvil. If the projectile comes to a sudden
drop or even sudden reduction of velocity the block if unrestrained
will, according to the principle of inertia, keep on going till
something stops it. The something in this case is the anvil and the
fulminate cap is set off. But it is not so simple. For while the
projectile is in flight it is acted upon by the air resistance and
slows down but the block in the cavity of the head is not subjected to
this resistance. It therefore gains on the projectile or creeps forward
in the cavity unless restrained as it is by a spring. Now one more
point and this type of fuze is complete. We supposed that our block
was free to slide. For safety’s sake it is pinned to the cavity. Again
we call upon inertia to bread the pin so as to leave the block free
to slide. The strength of the pin is calculated so that the force of
inertia of the mass of the block is greater than the resistance of the
safety pin and when the projectile starts the pin breaks and the spring
forces the block to the rear of the cavity until the sudden stop of
the projectile permits the block to slide forward as explained. Such a
fuze requires a comparatively high initial velocity and is not adapted
to howitzers using low muzzle velocities.

There are three other methods in use to arm the fuze. They are =inertia
of a sleeve=; =centrifugal force= and =powder pellet system=, that is,
combustion of a grain of powder holding the sliding block from the
anvil by means of an arm resting against the unburned powder grain.
These are more sensitive than the type described.

=In the first system=, a sleeve fitting around the plunger carrying
the cap slides to the rear by inertia when the projectile starts and
two clips engage in notches on the plunger body making the sleeve and
plunger thereafter move as one body, they are thus held together by
a plunger spring which before arming held the plunger away from the
anvil. The safety spring held the sleeve and plunger away from the
anvil and after arming prevents forward creeping by the plunger and
sleeve now locked together. Upon striking, the plunger and sleeve move
forward as one body and the cap strikes the anvil.

=In centrifugal systems= the primer plunger is kept safely away from
the anvil by a lock which is kept in place by springs. When the
rotational velocity reaches a certain point the force of the springs
is overcome by the centrifugal force and the locks are thrown aside or
opened and the plunger is free to move forward on impact.

=In the powder pellet system= (the one largely used by the Germans)
there is a well or channel filled with compressed powder, this is set
off by a fulminate cap which is fired by inertia, a small plunger-anvil
striking the cap. When the powder is consumed it leaves a channel
into which an arm attached to the sliding block carrying the igniting
fulminate for the charge may slide, thus permitting the block to slide
forward to the anvil fixed in the forward part of the cavity. It is
held from creeping forward after the compressed powder is burned by a
safety spring, thus insuring sufficiently hard an impact to set off the
cap.

Heretofore in our service the fulminating cap has been fixed and the
plunger carried the anvil or as we call it the firing pin. Such is now
the system in our base detonating fuzes, and in our combination fuze.

The new point detonating fuzes are patterned after the French and are
practically French fuzes.


Fuzes Classification.

Fuses are classified as:

(a) Percussion if it acts on impact, producing a low order of explosion.

(b) Time when it acts in the air at a certain point of the trajectory.

(c) Combination if it is able to act in the air or upon impact.

(d) Detonating when it contains a fulminate which will bring about
detonation upon impact.

The detonator may be separate or incorporated in the fuse. For the
75-mm gun and the 155-mm howitzer it forms a part of the fuze.

Many fuzes are armed on set-back. An exception to this is the long
detonating fuse, MK 111, which is armed by the unrolling of a brass
spiral holding together two half rings made of steel so fitted as to
prevent the anvil and the head of the fuse from getting close together.
The spiral unrolls when the rotational velocity of the projectile
reaches a certain speed, thus drawing away the two steel rings and
arming the fuse.

[Illustration: _DETONATING FUZE—MARK-III._]

[Illustration: _DETONATING FUZE—MARK-V._]

It is of great importance that the spiral spring be not unrolled during
transportation or storage. This is prevented by winding a tape of
tarred canvas around the spirals, the head being covered by a thin
band of tinfoil. Just before loading the projectile the head and tape
are removed by pulling the free end of the tape.

The following precautions concerning fuses must be rigidly observed to
prevent grave accidents:

1. All detonators and detonating point fuses must be fitted with a felt
washer underneath, thus insuring proper seating in the central tube.

2. Never disassemble a fuse by unscrewing.

3. Any fuse, the parts of which have become accidentally unscrewed,
must be destroyed at once. If fired it may cause a premature burst; if
handled a grave accident may result.

4. Any fuse or projectile which has been fired is dangerous, because it
may then be able to detonate by a very slight shock. It is forbidden to
touch it.

5. Never remove the tin hood from the long fuse before having screwed
the fuse in the central tube.

6. After having removed the tin hood, be sure that the spiral is in its
proper position. Never use a long fuse without the spiral.

7. Be sure the men understand that this spiral must not be removed. It
has happened that men have removed this spiral, thinking that it was a
device similar to the safety ring in trench mortar fuzes, MK VII E.

8. See that the ring of the long fuze which connects the powder train
to the fuze body cannot be unscrewed. If it can be unscrewed the fuze
should be sent back to the depot.

9. If it is necessary to remove a shell with a long fuze by means of
the rammer, be sure to have a special rammer cup in the shape of a
hollow cylinder of wood which will fit between the shell and the rammer.

10. Time and combination fuzes cannot be made absolutely water-tight;
the cover must therefore not be removed until the projectile is about
to be loaded.


Fuse Tables.

Tables showing American and French fuses to be used by our Field
Artillery, with information concerning markings, color, time of delay,
size of fuse, etc.


DETONATING FUSES.

  —————————————————————————————+——————————————————————+—————————————
         Time of delay.        |        Color.        |Size of Fuse.
  —————————————————————————————+——————————————————————+—————————————
  MK I                    2-100| White head.          |   Short.
                               |                      |
  M II (non delay)        2-100|                      |
  MK II (non delay)       2-100| White top.           |   Short.
  MK II (short delay)     5-100| Black top.           |   Short.
  M II (long delay)      15-100| Black head.          |   Short.
  MK III (Supersensitive)  zero| No color.            |   Long.
                               |                      |
                               |                      |
                               |                      |
  MK IV (non-delay)       2-100| White top.           |   Short.
  MK IV (short delay)     5-100| Black top.           |   Short.
  MK IV (long delay)     15-100| Black top violet     |   Short.
                               |   detonator socket.  |
  MK V (non-delay)        2-100| White top.           |   Short.
                               |                      |
  MK V (short delay)      5-100| Black top.           |   Short.
                               |                      |
  Mark—VII (non delay)   2-100 | White.               |   Short
  Mark VII (long delay)  20-100| Black top with violet|   Short
                               |   detonator socket   |
  —————————————————————————————+——————————————————————+—————————————

  —————————————————————————————+——————————————————+———————————————————
         Time of delay.        |Corresponding to. |      Cannon.
  —————————————————————————————+——————————————————+———————————————————
  MK I                    2-100| Russian 3GT.     | 3” gun for target
                               |                  |   practice only.
  M II (non delay)        2-100|                  | 8”, 9.2”,
  MK II (non delay)       2-100|                  | 204-m/m.
  MK II (short delay)     5-100| Modified.        | Gun and Howitzer.
  M II (long delay)      15-100| Russian.         |
  MK III (Supersensitive)  zero| French IAL.      | 75 G; 3.8”G and H;
                               |                  | 4.7 in. G and H
                               |                  |   6”H; 155H; all
                               |                  |   gas shells.
  MK IV (non-delay)       2-100| French 24/31     | Howitzer only.
                               |  SR (99-15).     |
  MK IV (short delay)     5-100| French 24/31     | Howitzer only.
                               |  AR (99-15).     |
  MK IV (long delay)     15-100| French 24/31     | Howitzer only.
                               |  SR (99-15).     |
  MK V (non-delay)        2-100| French 24/31     | All guns, but not
                               |  SR (99-08).     |   Howitzers.
  MK V (short delay)      5-100| French 24/31     | All guns, but not
                               |  AR (99-08).     |   Howitzers.
  Mark—VII (non delay)   2-100 |                  |          6” T. M.
  Mark VII (long delay)  20-100|                  |          6” T. M.
                               |                  |
  —————————————————————————————+——————————————————+———————————————————

  Letter “E” after mark VII indicates safety device.

  Note:—All American point detonating fuses are stamped on head cap in
  letters and figures, .125 in high, with name of use, amount of delay,
  initials of loader, lot and number; thus: PDF. MIV, xx Delay, FA,
  Lot No. xx.

[Illustration: 45-SECOND COMBINATION FUZE MARK I.]

[Illustration: _21 SECOND COMBINATION FUZE MODEL OF 1907 M._]


COMBINATION FUSES.

  —————————————————————————+——————————+—————————————————————
                           |Total time|
           Fuse.           | burning  |    Corresponding
                           |   Sec.   |     French Type.
  —————————————————————————+——————————+—————————————————————
  21 s/comb. F. A., 1907 M.|   21     | 22/31M 1897, 24 sec.
  21 s/comb. F.A., 1915    |   21     | 22/31M 1916, 24 sec.
                           |          |     AA.
  31 s/comb. F. A. 1915    |   31     | 30/55M 1889, 40 sec.
  45 s/comb. F. A. 1907 M. |   45     | Same as above.
                           |          | 30/55M 1889, 40 sec.
                           |          | 30/55M 1913, 40 sec.
                           |          |     AA.
  —————————————————————————+——————————+—————————————————————

  ——————————————+————————————————+——————————————————+———————
     Fuse.      | On what        | By what cannon   | Wt. of
                |projectile used.|      fired.      |  fuse.
  ——————————————+————————————————+——————————————————+———————
  21 s/comb.    |                |                  |
  F. A., 1907 M.| Com. Shrapnel. | All 3” and 75-mm | 1¼ lbs.
  21 s/comb.    |  MKi.          |  guns            |
  F.A., 1915    | Com. Shrapnel. | All 3” and 75-mm | 1¼ lbs.
  31 s/comb.    |  MKi.          |  guns            |
  F. A. 1915    | Com. Shrapnel. | 4.7” gun.        | 2 lbs.
  45 s/comb.    |                |                  |
  F. A. 1907 M. |                |                  |
                | Com. Shrapnel. | 155 How.         |
                |  MKi.          |                  |
                | C. S. Shell AA | 4.7” gun         |
                |  MKiii         |  Anti-aircraft.  |
                | AA. Shrapnel.  |                  |
  ——————————————+————————————————+——————————————————+———————


ACTION OF AMERICAN AND FRENCH DETONATING FUSES.

  ———————————+——————————+————————————————————+———————————
  Time       |   zero   |   1/100            |   2/100
  Color      | No color.|    Red.            |   White.
             |          |                    |
  American   | MKii     | None being made.   | MK i
  Detonating |          | Fuse is considered | MK ii (ND)
             |          |     unsafe         | MK iV (ND)
             |          |     safe           | MK iV (ND)
  Fuses      |          | Will be abandoned  |
             |          |     by French      | MK V (ND)
  French     | iAL.     |   1                |   SR.
  detonating |          |                    |
  fuses      |          |                    |
  ———————————+——————————+————————————————————+———————————

  ———————————+————————————+———————————————
  Time       |   5/100    | 15/100
  Color      |   Black.   | Black with
             |            | violet socket.
  American   | MK ii (SD) | MK ii (LD)
  Detonating | MK ii (SD) | MK iv (LD)
             | MK V (SD)  |
             | MK V (SD)  |
  Fuses      |            |
             |            |
  French     |   AR.      |   LR.
  detonating |            |
  fuses      |            |
  ———————————+————————————+———————————————


Notes on Ammunition Marking.

=Marks on H. E. Shell.= These are of two kinds.

(a) Stamped marks made with a steel punch on the body of the projectile
just above the rotating band. These refer to the manufacture of the
projectile.

(b) Painted marks or bands which are clearly visible. They refer to the
loading, to the weight of the projectile and to the special purposes
for which the projectile is to be used.

Painted marks referring to loading are found on the ogive.

H. E. shells are usually painted red.

Marks referring to weight are painted in black just above the rotating
band, as follows:

    L.—very light.
     +—light.
    ++—normal.
   +++—heavy.
  ++++—very heavy.

A white cross above these marks means that a plate has been welded on
the base. These marks are also painted on the boxes.

Shells fitted with cartridge cases (fixed ammunition) are not painted
below the rotating bands.


Special Shell.

Incendiary shells.—These incendiary shells are filled with some
flame-producing liquid, alumino thermic charge or incendiary cylinder
composed of slow burning linstock and string strongly impregnated with
saltpeter.

Markings.—Green with red ogive.

All shells containing black powder are more or less incendiary.
Percussion shrapnel is incendiary.

[Illustration: 75-mm Ammunition.]

Star Shells.—For 155 howitzer. Upon bursting, they liberate eight
white stars fitted with silken parachutes. The stars are projected
backward through the base of the projectile at the point of burst.
The parachutes open, the stars descending very slowly, illuminating the
surrounding objects for about 45 sec. The best height of burst is about
300 m.; the burst interval should not be over 300. These shells are
also incendiary. Markings: a blue star and an “E.”

Gas shells are either toxic or tear-producing.

(a) Toxic shells are numbered either 4 or 5. The liquids 4 and 5
volatize, immediately upon contact with the air. The gases are quickly
diffused and easily carried by the wind.

Effect.—Liquid 4 acts immediately and is felt instantly.

Liquid 5, on the contrary, works more slowly and its effects are
apparent only after several hours. Markings: Green with white bands,
and numbers 4 or 5 on the ogive.

(b) Tear shells.—These shells are numbered 11, 12 and 13. They are
filled with two liquids, either mixed or separated, one liquid being
tear producing, the other smoke producing. When the shell bursts,
a greater part of the liquid is volatilized, the remainder being
projected to the ground in small drops which volatize with variable
speed. Markings: Green with numbers 11, 12 or 13 on the ogive.

Tracer shell.—This shell is fitted with a time fuse which ignites
the inside charge, the flames of which pass through the holes in the
ogive thus tracing the trajectory. Tracer shells are used in fire for
adjustment on aircraft. They are also incendiary. Markings: White with
blue ogive. Letter “T” painted on body.


PRECAUTIONS IN SEPARATE LOADING PROJECTILES.

All projectiles must be seated accurately and carefully in loading,
otherwise not only inaccurate fire will result but also premature
detonations may occur.

Rotating bands should be smoothed and lightly greased just before
loading. In transport and in storage the bands should be protected by
rope bands, straw tithes, etc., to prevent deformation.




CHAPTER XIII

CARE AND PRESERVATION.


OILS AND CLEANING MATERIAL, TOOLS AND ACCESSORIES FOR ARTILLERY
MATERIEL WITH THEIR USE.

In order that all parts of the materiel may function easily, it is
necessary that all the working and bearing surfaces may be properly
cleaned and lubricated with the appropriate lubricant. Where such
surfaces are not directly accessible, oil holes are provided; these
holes should be kept free from grit and dirt. Except during oiling,
they should be kept fully closed by the means provided.

For use in service, for the cleaning and preservation of this materiel,
the ordnance department issues hydroline oil, lubricating oil, clock
oil, vaseline, sperm oil, coal oil, neat’s-foot oil and light slushing
oil. Each of these oils are suited for the particular purpose for which
it is issued, as stated below, and care should be taken that it is not
used for other purposes.

=Hydroline oil.=—Used in the recoil cylinders of the carriage _and for
no other purpose_. Never used as a lubricant. It is characterized by
its low freezing point and its non-corrosive action on metals.

=Lubricating oil= (_Engine oil Number 1_).—A light petroleum oil used
exclusively in all oil holes of the materiel, and in lubricating such
parts as wheels and axles, guns and cradle slides, cradle pintle and
socket elevating and traversing mechanisms, exterior of cylinders,
brake bearings, hinges, different surfaces of breechblocks, threads,
breech recess, et cetera.

=Clock oil.=—Used on the spindle and all gearings of the Battery
Commander’s telescope, bearings of the panoramic sight, range quadrants
and fuze setters. In all cases clock oil should be used only when the
instruments mentioned are disassembled for cleaning. It should be
applied by dropping from the end of the dropper attached to the end of
the cork. In case of emergency, use as a substitute either sperm oil or
Engine oil No. 1, in the order mentioned.

=Vaseline= (=Petrolatum=).—The heavy petroleum oil free from rosin.
Used on the worm gears and the worm racks of the panoramic sight, the
hand and bracket fuze setter, B. C. telescope, and on the micrometer
screw and bushing of the quadrant. The spare parts of the breech
mechanism should also be coated with vaseline and each piece then
wrapped in paper to prevent the oil from being rubbed off.

=Sperm oil.=—A lighter lubricant than the lubricating oils, and may be
used on the gears of sights, fuze setters, ranges, quadrants, parts of
revolvers, et cetera; lubricating oil may also be used on such parts.
It is also used as a temporary rust preventive. Its low viscosity and
light body make it unsuitable for this purpose for more than a few days.

=Coal oil.=—Used for cleaning purposes. In the field it may be used for
lanterns. Coal oil for general illuminating purposes is furnished by
the quartermaster department.

=Neat’s-foot Oil.=—An animal oil used for softening and preserving
leather. Applied with a moistened cloth to the flesh side of moistened
leather.

=Light slushing oil.=—The heavy petroleum oil similar to cosmic. Used
as a rust preventive. Essentially a mineral oil containing a large per
cent of rosin. Prescribed for use in the protection and preservation of
all bright or unpainted of steel or iron on all parts of the equipment
when the materiel is to remain unused for an appreciable length of
time. Its use as a lubricant for mobile artillery is forbidden.
Before applying the slushing oil to any surface, the parts should be
thoroughly cleaned so as to be free from rust, coal oil, lubricating
oil, et cetera, as their presence will cause rusting under the slushing
oil. The slushing oil should then be applied in a thin, uniform coat,
since this is all that is necessary to give good protection. Except
in very cold weather it can be applied by using a paint brush as when
painting, in cold weather it should be applied by stippling—that is, by
holding the brush perpendicular to the surface to be coated and then
tapping the surface with the point of the brush. It can be applied
through the bore of the gun by a slush brush issued for that purpose.
In cold weather it should be warmed before used in the bore of the gun.
It may be readily removed by burlap or waste dipped coal oil.

=Borax.=—Issued for use as a flux in welding.

=Lavaline.=—A metal polish issued interchangeable with Gibson’s soap
polish. Used on bits and collars.

=Lye, powdered.=—When dissolved in water, one pound to six quarts with
sufficient lime to give a consistence of paint, is used to remove old
and blistered paint.

=Napthaline.=—A moth preventive, effective only after eggs and grubs
already present have been removed. Used in the storage of blankets, et
cetera.

=Polish, Gibson’s Soap.=—A metal polish issued interchangeably with
lavaline. Used on bits and collars.

=Paint, rubberine.=—Used in connection with loading ammunition in
accordance with instructions regarding the same.

=Primer, brown enamel.=—A hard, quick drying enamel used for painting
parts of horse collars, draft springs, et cetera.

=Sal Soda, Bicarbonate of Soda.=—A saturated solution of soda and water
makes an alkaline solution that will not rust. The solution must be
saturated, that is, at least 20% or one-fourth pound of soda (6 heaping
spoonfuls to one cup of water). This solution is an effective solvent
of powder fouling and should always be used after firing, whether metal
fouling solution is to be used or not. It reduces the labor of cleaning
with oil alone by more than half. Used also in a weaker solution
(one-half pound to 8 quarts of water) in washing surfaces to be painted
and to remove dirt and grease.

=Soap, H. & H.=—A neutral naphtha soap used in washing blankets, web
and cloth equipment. Applied in the form of a solution (one cake to 9
cups of hot water). If for any cause this soap is not obtainable, a
good laundry soap (ivory or equal) may be used, but in no case should
yellow soap containing a large percentage of alkali be used.

=Soap, castile.=—An alkaline soap used in cleaning leather equipment.
Applied on a moistened sponge.

=Soap, saddle (Hollingshead).=—A soap used as a dressing for leather
equipment. Applied with a thick lather on a moistened sponge.

=Swabbing solution, contains.=—Ammonium persulphate, 60 grains or one
half spoonful smoothed off. Ammonia 28%, 6 oz. or ⅜ of a pint or 12
spoonfuls. Water, 4 oz. or ¼ pint or 8 spoonfuls. Dissolve the ammonium
persulphate in the water and add the ammonia. Keep in a tightly corked
bottle. Pour out only what is necessary at a time and keep the bottle
corked.


TOOLS AND ACCESSORIES.

In the repair of all equipment, it is literally true that “a stitch
in time saves nine,” and that a timely repair will save the entire
article.

=Tool Kits= will be kept complete and serviceable; edges of cold
chisels free from nicks; drifts and punches properly shaped immediately
after using; and files kept clean.

To prevent unscrewing, _copper wire_ is used to lash nuts and other
threaded parts which are not secured by split pins.

=Contents of Leather Pouch for Spare Parts (carried in Trail Boxes of
3-inch Guns)=:—

For Breechblock—

  50  Split pins
  1  Block latch and spring
  1  Firing pin and spring
  1  Firing pin sleeve
  2  Handy oilers, 5-16 inch
  1  Hinge pin catch
  1  Lever latch spring
  1  Locking bolt, nut and pin
  1  Locking bolt spring
  2  Oil hole covers with screws
  1  Pallet pin
  1  Sear
  2  Trigger shaft detent

For Hand Fuze Setter—

  2  Corrector scale screws
  1  Guide plate lock screw
  2  Index bar screws
  1  Index plunger and spring
  2  Oil hole screws
  1  Range index
  3  Range ring screws
  1  Stop pin screw

For Bracket Fuze Setter—

  1  Corrector scale screw
  3  Guide screws
  4  Housing screws & split washers
  1  Knob washer
  1  Range worm crank & knob taper pin
  1  Range worm crank handle
  2  Range ring screws
  3  Split pins (0.125)
  1 Spring and spring cover with screw
  2 Stop pins with rivets

For Cylinder—

  1 Drain-plug, cylinder
  1 Elevating & traversing lock spring
  1 Filling plug (piston rod)
  5 Rings Garlock packing, ¾ in

=Special Wrenches=, =Spanners=, other tools and accessories will be
used only for the purposes for which they are intended. This purpose is
usually stamped upon the tool.

In assembling or disassembling parts of the materiel, no part will be
struck directly with a =hammer=. If force is necessary, a piece of
_wood_ or _copper_ should be interposed between the hammer and the part
struck. All nuts are provided with _split pins_ as keepers.

A pair of =wire cutting pliers= is provided for use in pulling split
pins, cutting wire lashings, etc. When a nut is assembled the split pin
should always be inserted and properly opened.

=Axes, hatchets, picks, pick mattocks and shovels= are carried on the
carriage for use in the field and will not be put to other uses. The
working edges will be kept bright and lightly oiled, the edges being
sharpened if intended for cutting, or smooth if intended for digging.
_Deformed blades_, _edges_ or _points_ should be straightened at the
anvil and forge or in a vise. _Shovel points_ are straightened with a
hammer on a block of wood.

The _side edges_ of _shovel blades_ should not be used as a mattock,
as such treatment will deform the blade. In the field, _split handles_
should be wrapped with a cord until they can be replaced by new handles.

_Canvas Buckets_ are used for watering animals, for washing carriages
and equipment. Whenever possible, they should be dried before folding
and replacing in the holders on the carriages.

A rip or hole may be patched and made practically water-tight by a coat
of shellac.

_Lanterns_ are used for illuminating purposes in the field only.

_Paulins_ are used to cover the harness and guns when in the field or
in park. On the march they are carried on the carriages, being folded
to serve as seat cushions. Holes and tears should always be properly
sewed, stitched or darned as soon as practicable.

_Picket Ropes_ are used in the field as drag ropes for the carriages
or as picket lines for the animals. The ropes must be in a serviceable
condition and free from knots. To keep them in a serviceable condition,
splicing may often be necessary.


CARE AND CLEANING OF THE DIFFERENT PARTS OF THE CARRIAGES.

=To disassemble and to clean the cylinder.=—For cleaning, the cylinder
is dismounted and emptied and the cylinder head, counter recoil buffer,
and piston rod removed. The interior of the cylinder, the piston, the
counter recoil buffer and the stuffing box should then be thoroughly
cleaned by the use of cotton waste. The removal of the packing is not
necessary in cleaning. The cylinder bore should be carefully inspected,
and if any rust has formed it should be removed with coal oil, using
if necessary, fine emery cloth. The latter must be used with great
care to prevent any increase in the clearance between the piston and
the cylinder. If rubbing, burring, or scoring of the parts is noted,
the rough spots should be carefully smoothed down by a skilled workman
with a dead smooth file or with emery cloth, and the cause of the
roughness ascertained and removed. Where unusual rubbing or scoring has
occurred, the facts will be reported to the Officer of the Ordnance
Department charged with the duty of keeping the battery in repair,
for his information and action. The exterior of the cylinder should be
kept well oiled and free from rust and dirt, and an inspection made at
least once a month to ascertain its condition. Where rust has formed it
should be removed with coal oil, and, if necessary, emery cloth. For
shipment or storage, or where the carriage is to stand without firing
for extended periods, the cylinder should be coated with the light
slushing oil used for the bore of guns.

=To fill the recoil cylinder.=—If the cylinder is not completely
filled, loss of stability will occur and higher stresses than normal
will be developed in the carriage. For this reason the cylinder
should be filled with the greatest care, a commissioned should,
himself, verify that the cylinder is full and that no air is left in
it, exception of the void noted below. It is far easier to fill the
cylinder when it is disassembled from the cradle. If assembled in the
cradle, bring the gun to its maximum elevation and remove both filling
and drain plugs. It is necessary that the drain plug holes should be
lubricated on top of the cylinder. Fill through the hole in the piston
rod. Allow a few minutes for the air to escape and the oil to settle.

Refill and repeat two or three times. When satisfied that the cylinder
is entirely full of oil, insert both plugs, and depress the gun to its
maximum depression. After a few moments elevate again to its maximum
elevation and unscrew both plugs. Now refill as described above. When
entirely full, allow not more than two cubic inches (about one-fourth
of a gill) of the oil to escape, insert both plugs and lash them with
copper wire. It may happen that after firing a few rounds the gun
will not return to battery. This may be due to, first, weakness of
springs, second, stuffing box gland being screwed up too tight, or
third, the oil having expanded, due to heat. It any case the cause
must be ascertained and remedied, if due to expansion of oil, it is
proven by the fact that the gun cannot be pushed into battery by force
exerted on the breech of the gun. In that case elevate the gun to
its maximum elevation and remove the filling plug. The oil will now
escape permitting the gun to return to battery. In emergencies, water
may be used in the cylinder. This should be done only when absolutely
necessary, and never in freezing weather, and as soon as practicable
the cylinder should be emptied, cleaned, and thoroughly dried and
filled with hydroline oil. About 9 pints of hydroline oil are required
for filling the recoil cylinder.

=To empty the recoil cylinder.=—The cylinder may be emptied either when
assembled or disassembled from the cradle. In either case, remove both
the filling and drain plugs, depress the forward end of the cylinder
and drain the contents into a clean can or other receptacle over which
a piece of linen or muslin has been stretched, for straining the oil.

=To clean the recoil cylinder oil.=—The hydroline oil used in the
cylinder should be cleaned and free from grit and dirt. The oil should
be stored in the closed cans provided for the purpose, and be carefully
protected from dirt, sand, or water. Oil withdrawn from the cylinders
and containing any sediment must not be used again until it has been
allowed to settle for not less than 24 hours. When sediment has thus
been permitted to settle great care must be taken not to disturb it
in removing the oil. To insure the cleanliness of all cylinder oil it
should be strained through a clean piece of linen or muslin before
using.

=To clean the bore of the gun.=—After firing and at other times when
necessary, the bore of the gun should be cleaned to remove the residue
of smokeless powder, and then oiled. In cleaning, wash the bore with a
solution made by dissolving one-half pound of Sal Soda in one gallon
of boiling water. After washing with the soda solution, wipe perfectly
dry and then oil the bore with a thin coating of the light slushing
oil furnished for that purpose. Briefly stated, the care of the bore
consists of removing the fouling resulting from firing, in obtaining
a chemically clean surface and in coating this surface with a film of
oil to prevent rusting. The fouling which results from firing of two
kinds—one, the production of combustion of powder, the other, copper
scraped off the rotating band. Powder fouling because of its acid
reaction, is highly corrosive, that is, it will induce rust and must be
removed. Metal fouling of itself is unactive, but its presence prevents
the action of cleaning agents. It should be removed if it accumulates.
At every opportunity in the intermission of fire, the bore of the gun
should be cleaned and lubricated.

=To clean the breech mechanism.=—The breech mechanism should be kept
clean and well lubricated. It should be dismounted for examination and
oiled when assembled.

=To clean the recoil springs.=—Dismount to clean. All rust should
be removed and the springs well oiled before assembling. When the
springs are dismounted the interior of the cradle should be cleaned and
examined for defective riveting, missing rivet heads and scoring. The
condition of the spring support guide should be noted and all burrs or
scores carefully smoothed off.

=To clean, lubricate and care for the elevating and traversing
mechanism.=—The contact surfaces between the cradle and the rocker
should be kept clean, thoroughly oiled, and free from rust. If
indications of rusting, cutting, or scoring of these surfaces appear,
the cradle should be dismounted, the rust removed, and rough spots
smoothed away. The elevating and traversing mechanisms should be
dismounted for thorough cleaning and overhauling. They should be kept
well oiled and should work easily. If at any time either mechanism
works harder than usual, it should be immediately overhauled and the
cause discovered and removed. In traveling, the cradle should be locked
to the trail by means of the elevating and traversing lock, so as to
relieve the pointing mechanism of all travel stresses.

=To clean, lubricate and care for the wheels.=—The wheel and wheel
fastenings should be dismounted periodically and the fastenings, hub
boxes, axle arms, and axle bore cleaned and examined. All roughness due
to scoring or cutting should be smoothed off. The hollow part of the
axle acts as a reservoir for the oil to lubricate the wheel bearings.
Experience will show how much oil is needed, but enough should be used
to insure that the oil will pass through the axle arms to the hub caps.
The nuts on the hub bolts should be tightened monthly during the first
year of service and twice a year thereafter. The ends of the bolts
should be lightly riveted over to prevent the nut from unscrewing.
When the hub bolts are tightened, the hub band should be screwed up as
tightly as possible against the lock washer at the outer end of the hub
ring.


GENERAL INSTRUCTIONS FOR THE CARE AND MAINTENANCE OF MATERIEL


Assembling and Disassembling.


(a) Cradle mechanism, cylinder, springs et cetera.

All work upon recoil cylinders, sights, and other optical equipment
should be done in the presence of a commissioned officer. The recoil
cylinder should never be clamped in a vise, but when necessary to
hold it from turning, a spanner applied to the front end of cylinder
should be used. Never remove the cylinder end stud nut when the piece
is at an elevation. See that proper kind of oil is used in cylinders
and for lubrication. Strain the oil used in filling the cylinders
through a fine clean cloth and be sure that the receptacles used
in handling the oil are clean. Take every precaution to keep the
interior of the cylinders clean and to prevent the entrance of foreign
particles. In assembling the gland be sure that at least four threads
of the gland are engaged with the threads of the cylinder head. Lash
parts with copper wire to prevent unscrewing. Close down the ends of
the recoil-indicator guide to avoid loss of the indicator. Prevent
possible injury to cannoneers by causing them to stand clear of the
counter-recoil spring column in assembling or dismounting. Remove
cylinder end stud screw before trying to unscrew cylinder end stud.


(b) Gun

In moving the gun on or off the cradle, provide ample support for the
breech end, so that the gun clips are in prolongation of the cradle
guides; if this is not done the cradle guides may be ruined.


(c) Elevating and traversing mechanism.

If the gun will not remain at the elevation at which set, the crank
shafts are probably not correctly assembled. If the elevating screw do
not house in traveling, they are incorrectly assembled.


(d) Sights and quadrant.

Frequently verify the adjustments of sights and quadrant. Require
special care in handling sights. Do not permit cannoneers to use front
sight as a handle in mounting. Be sure that the range disk of the
quadrant and range strip of the rear sight shank are graduated for the
particular type of ammunition used by the battery. This also applies to
the fuze setter.


Care of Materiel.


(a) Parts of the Carriages.

All nuts are secured by split pins, which should be replaced and
properly opened when nuts are screwed home. Do not strike any metal
part directly with a hammer; interpose a buffer of wood or copper. All
working and bearing surfaces of the carriage require oiling; those
not directly accessible for this purpose are provided with oil holes
closed by spring covers or handy oilers. Do not permit brake levers
to be released with a kick or blow. It has been found that the apron
hinges occasionally become broken, and that the apron hinge pins are
frequently lost. Whenever this happens the hinge or hinge-pins should
be immediately replaced. For if this is not done the apron, which is
very expensive is apt to become cracked or broken. When the lunette
becomes loosened the lunette nuts should at once be tightened.


(b) Wheels.

Keep hub bolts and hub bands properly tightened. To tighten the hub
bands screw them as tightly as possible with a wrench and then force
them farther by striking the end of the wrench with a hammer. All
wheels and pintle bearings should be frequently oiled.


(c) Inspections.

Battery commander should frequently make a detailed inspection of all
the vehicles in the battery, to see if any parts of them are broken or
if any screws, nuts, split-pins, et cetera are missing. If any such
defects are found they should immediately take steps to replace missing
or broken parts. At these inspections the material should also be
examined to ascertain whether the cleaning schedules have been properly
carried out. Compliance with these instructions will do much toward
prolonging the life of the carriage.


Firing, Precautions and Preparations for.

Before firing, inspect to see that cylinders are properly closed and
that the cylinder end stud nut and piston rod-nut are in place. If time
permits, oil slides before firing. Note length of recoil for the first
few shots to be sure that the recoil mechanism is working properly.
There is no danger as long as the recoil does not exceed 48 inches.
Therefore, for first shot always set recoil indicator for about 42
inches. If the gun fails to return fully into battery, it is probably
due (1) to dirt on slides and guides, (2) to cutting of slide surfaces
on account of lack of oil, (3) to gland being screwed up too tightly,
(4) to dirt or foreign particles in the cylinder, and especially in
the counter recoil buffer recess, (5) to weakness of springs, 90% of
such cases will be found to be due to 1, 2 or 3. Lock the cradle to the
trail at drill and at traveling to avoid unnecessary strain upon the
pointing mechanism. After unlimbering, release elevating and traversing
lock before attempting to elevate or traverse gun.


Cleaning and Care of Leather.

All leather contains more or less oil. When the amount of oil decreases
the leather becomes harder, less pliable, and shows a tendency to
crack. It loses its elasticity and breaks more readily under sudden
strains. Exposure to the sun evaporates the oil and exposure to the
rain washes it out, both conditions tending in the long run to bring
the same result, namely, hardening and stiffening of the leather.
Accumulations of foreign substances are very injurious for they tend to
absorb the oil from the leather underneath, leaving it dry and hard, or
they retain moisture on the surface, prevent the air from getting to
it and rot the leather. Also many substances such as perspiration and
excretion from the horse contain chemicals which are very injurious.
For these reasons all leather must be kept clean. The cleaning agent
used is castile soap with water. All pieces should be taken apart and
as much dirt and dust as possible removed with a damp sponge or cloth.
All remaining dirt is then removed by washing with castile soap and
water. In doing this always use as little water as possible. Wring
the sponge out nearly dry, rub it on the soap and work it with the
hands until a thick, creamy lather is formed. Then scrub the leather
thoroughly until all dirt is removed. Special care should be taken
around spots that have been in contact with metal perspiration or
excreta. If there is an old accumulation of dirt a soft stick may be
used to scrape this off. Never allow a knife or a piece of glass to be
used or any sharp edged instrument. After all dirt is removed run the
sponge in one direction, all the way along the leather to remove all
remaining dirt and extra lather. Never allow the pieces to be rinsed
off in a bucket of water. Metal parts should be washed thoroughly and
dried and if necessary any rust removed with a crocus cloth. Although
as little water as possible is used some of the oil in the leather will
certainly be washed out, and, to keep the leather in proper condition,
it must be replaced. After an ordinary cleaning this is normally
done by an application of saddle soap. Saddle soap is not a cleaning
agent—only a dressing for leather. It contains enough oil to replace,
if properly applied, all loss through ordinary use. It is used in the
same manner as castile soap, in the form of a thick, creamy lather,
rubbed well into the leather and allowed to dry. The leather should be
well rubbed with the hands while drying, to keep it soft and pliable,
and to work the oil in. Always allow it to dry in the shade, preferably
for several hours, and never assemble pieces, especially fastening
straps into buckles until thoroughly dry. Oil is never applied directly
to leather unless it has become so hard and dry that saddle soap is
not sufficient to soften it. There is only one oil issued for that
purpose. That is “Neat’s Foot Oil.” This should only be applied to the
flesh side of the leather and very lightly. Several light applications
give much better results than a few heavy ones. The oil should be
well rubbed in with the hands and should be preferably applied after
cleaning the leather with castile soap and water, as the pores of the
leather are then more open and the oil penetrates much better. Never
oil leather until it becomes greasy, for, besides wasteful, it makes
the leather too spongy. In emergencies, where Neat’s Foot Oil cannot be
procured any good vegetable oil may be used, preferably olive oil. This
is only for emergencies and is not to be used unless Neat’s Foot Oil or
saddle soap cannot be had. All new leather equipment should be cleaned
with castile soap and water as soon as unpacked as leather very often
becomes covered with mold after being packed in boxes for some time.
Ordnance leather as it comes to the battery is very dry and should be
thoroughly oiled before being used. New equipment after being washed
thoroughly, should be given, in several light applications as much oil
as it will absorb without becoming greasy. Each application should be
allowed to dry thoroughly and should be given frequent rubbings to
soften the leather. With the proper kind of preparation for use there
is no excuse for the large amount of broken new leather equipment which
is so common. In packing harness for shipment, especially into harness
sacks the harness should be cleaned and oiled and then dried for at
least twenty-four hours before putting into the sacks. After removing
from the sacks at the destination, cleaning and dressing with saddle
soap is sufficient. When the leather is dirty, clean it—not to improve
its looks but to preserve it. When wet allow it to dry in a warm (not
hot) place, in cold weather; or in the shade in summer. When it is dry
apply saddle soap or oil. Never hang any piece of equipment over a
nail or sharp edge as cracks always develop where the leather has been
folded over sharply. Ordinary oils and greases rot leather, so all such
equipment must be kept away from contact with them. Never leave any
piece of leather where it will chafe against any sharp edge or corner
and never leave it exposed to the sun longer than necessary.


Care of Cloth Equipment.

All cloth equipment should be kept as clean as possible by continual
brushing. The fewer times necessary to wash it, the longer its life.
Canvas goods such as paulins, webbing, etc., when it becomes necessary
to wash them should be scrubbed with Paco, or H. & H. soap and water.
Make a solution of one cake of either soap in nine cups of hot water.
Brush the article to be cleaned thoroughly and spread it on a clean
table. Scrub with the above solution and scrubbing brush until a good
lather appears. Rinse in clean water and hang in the shade to dry.
Woolen articles may be cleaned in the same manner or with ordinary
laundry soap. The first method being always the best. It is preferable
to wash these in cool or warm water, as hot water shrinks them. Never
wring woolens out, but after washing, rinse in clean water and hang
immediately up to dry. Saddle blankets should be kept well brushed and
should be frequently unfolded, hung in the sun and beaten with a whip.
When removed from the horse they should be doubled over with the wet
side out and put in the shade to dry. If no shade is available, and
they must be exposed to the sun, always fold the wet side inward. With
these precautions, saddle blankets should not need washing oftener
than twice a year. In washing immerse the blanket in tepid soap suds
repeatedly until clean, rinse in clean water, and hang in the sun to
dry. Do not scrub the blanket.


Care of Metal.

All metal equipment should be kept clean and free from rust. Coal oil
is used to remove rust, but it must always be removed as it will rust
the metal if allowed to remain. The coal oil should be applied to the
metal and if possible allowed to remain for a short time. This will
loosen and partially dissolve the rust so that it can be rubbed off
with a rag or a sponge. Continued applications may be necessary if
there is much rust. A solution of Sal Soda is also a good rust remover.
The articles must be washed thoroughly after using this to remove
all traces of the soda as it is a very active corrosive. Never scour
metals to remove rust if it can be avoided as this leaves a roughened
surface which will rust again much more easily. Polished surfaces such
as brass fittings should be cleaned and polished with Lavaline. This
may also be used on the bearing surfaces of steel collars. All surfaces
after cleaning should be dried thoroughly and if not painted should
be greased with cosmis or cosmoline. These form an air-proof coating
over the metal surface so that no moisture may reach it and cause
rusting. If the metal is not dried thoroughly, some moisture may be
held between the grease and the metal surface which will in time cause
rust to appear. Care must be taken that the grease covers the surface
completely. All surfaces against which there is no friction should
be painted and kept so. Ordinary olive drab or collar paint is very
satisfactory for this purpose.


Care of Guns During and After Firing.

Always while firing keep the bore as clean as possible. If there is
time to swab out between shots, do so. During continued firing a
bucket of water should be kept near the gun, and the sponge on the
rammers staff kept wet while swabbing. Watch the recoil indicator and
occasionally push it ahead so as to be sure you are getting a correct
reading. Be sure that the gun returns fully into battery after each
shot. Keep the ammunition, and especially the rotating bands, free from
dust and dirt.

The rotating band should be greased very lightly with cosmis just
before inserting the projectile into the breech. In continued firing,
oil the slides frequently. Keep the fuze setter clean and be careful
that no dirt gets down around the stop pin. Examine the breech recess
frequently and wipe out all dirt and brass filing that may accumulate.
The gun should be cleaned thoroughly immediately after firing. Make
a solution of one pound of sal soda in one gallon of boiling water.
Remove the breechblock and carrier, and let one man clean and oil it
thoroughly while the rest of the gun is being cleaned. Remove the
sponge from the rammer staff, and over the brass rammer, fit a piece
of folded burlap. Fold this burlap as many times as you can and still
force it through the bore. Soak the burlap in the sal soda solution and
swab the bore out thoroughly. Be careful to remove all copper filing,
and the bore should be as bright as a piece of glass when finished.
After cleaning it is best though not absolutely necessary to swab out
with clean water. Then dry thoroughly with a dry swab, and grease every
exposed surface. In cleaning the breechblock and firing mechanism
always dismantle it completely. Clean and oil the slides, fuze setters
and all parts of the carriage. Decap the empty cartridge cases and wash
them out thoroughly with the sal soda solution. There is a decapping
set with every battery. Rinse out in clean water and set them in the
sun to dry.


A CLEANING SCHEDULE FOR MATERIEL.


Daily.


Before leaving the park:

1. Unlock boxes and chests and secure them with snaps.

2. See that all tools, paulins, etc., are secure.


After returning to the park:

1. Remove from carriages all dust, excess oil and mud. Examine for
missing nuts, split pins, broken parts and parts that need adjustment.
Make necessary repairs.

2. Clean and oil breech recess and breechblock; after firing, clean
bore with salsoda solution, wipe perfectly dry and oil.

3. Oil wheels, elevating and traversing mechanism, tools if necessary.

4. See that all oil holes are properly closed and that carriages are
ready for immediate use.

5. Clean and oil without dismounting; rear sight, quadrant and fuze
setter.

6. Lock all boxes and chests.

7. Signal detail: clean all instruments, oil all exposed bearing
surfaces. Test telephones and go over all wire used that day and repair
same by covering exposed parts. Have all instruments, wire etc., ready
for immediate use.

8. Clean all collars and bits and dry the blankets; wipe dirt from the
harness.

9. Clean and oil all pistols and revolvers that have been used that day.


Weekly.

1. Wash and clean entire carriage.

2. Disassemble and clear all oil breech mechanism. Always do so
immediately after firing.

3. Clean out and fill with oil, all oil holes of gun clips and cradle
pintle.

4. Clean all leather straps as you would clean harness.

5. Take apart and thoroughly clean all parts of harness.

6. Take apart and clean and oil all pistols and revolvers.

7. Clean with castile soap and harness soap all leather of the personal
equipment.


Monthly.

1. Disassemble the following and clean and oil: elevating mechanism,
traversing mechanism.

2. Pull from battery and clean and oil guide rails and clips. Trip gun
and test recoil.

3. Tighten all hub nuts and inspect wheels for dish.

4. Take off wheels, clean and oil axles and hubs. Replace hub liner
when necessary.

5. Dismount poles, double trees and spare pole, clean and oil.

6. Dismount rear sight bracket from support, clean and oil. Do the same
for the front sight.


Every Three Months.

1. Dismount, clean, oil and assemble the recoil mechanism.

2. Inspect the surplus kits and replace all articles that are not in
proper condition.

3. Unpack, clean, oil and repack the battery and store wagons, forge
limber.


Every Six Months.

1. Inspect all articles of the permanent camp equipment, dry, oil and
repair when needed. Pitch tentage for examination and drying.

2. Examine all articles in store such as leather, harness and spare
metal parts. Clean the harness, dub the leather, oil all metal parts.


PRECAUTIONS AND GENERAL INSTRUCTIONS.

1. Never allow steel parts to be struck with a steel hammer. Always use
a copper drift between the hammer and the steel part.

2. Never try to force a delicate part if stuck. The sticking is
probably due to rust and the parts can be loosened by soaking in coal
oil or by heating the exterior surfaces with a torch.

3. Be careful in using screw drivers or wrenches not to let them slip
and thus ruin the heads of the screw or nut.

4. Insist upon the rule that any part needing repairs be repaired
immediately upon arrival in garrison or camp.

5. Never allow a broken part to be stored except for the action of an
inspector or survey.

6. Before any article is put away for storage, have it thoroughly
inspected and make necessary repairs.

7. See that all articles of your equipment are always marked or stamped
with the insignia and the battery number.

8. Hold all members of your organization responsible for any
carelessness or negligence in the care of the equipment.




CHAPTER XIV

FIRE CONTROL EQUIPMENT.


SIGHTS.

The instruments provided for sighting and laying the gun include a line
sight, a rear sight, a front sight, a panoramic sight, and a range
quadrant.

=Line sights.=—The line sight consists of a conical point as a front
sight and a V notch as a rear sight, located on the top element of the
gun. They determine a line of sight parallel to the axis of the bore,
useful in giving general direction to the gun.

=Front and rear sights.=—The front and rear sights are for general use
in direct aiming. The front sight carries cross wires. The rear sight
is of the peep variety, constructed as follows: To the sight bracket
is attached the shank socket upon which a spirit level is mounted for
the necessary correction due to difference in level of wheels. The
sight shank consists of a steel arc, the center of which is the front
sight. It slides up and down in the shank socket and is operated by a
scroll gear. A range strip is attached to the face of the shank and is
graduated up to 6500 yards, least reading 50 yards. To the left side of
the shank is an elevation spirit level, permitting approximate quadrant
elevations to be given with the sight shank when the quadrant is out of
order.

The peep sight and its deflection scale are mounted above the shank.
This peep traverses along a screw operated by a knurled head. A socket
and ratchet are also provided for the attachment of the panoramic
sight.

[Illustration: _Rear Sight._]

Nomenclature of the important parts of the Rear Sight:—

  Peep sight
  Elevation level
  Deflection scale
  Peep sight screw and head
  Range strip
  Shank
  Shank socket
  Cross level
  Leveling screw
  Scroll gear and handle
  Rear sight bracket
  Panoramic sight socket and ratchet


PANORAMIC SIGHT, MODEL 1917.


Description.

=The panoramic sight= is a vertical telescope so fitted with an
optical system of reflecting prisms and lenses that the gunner can
bring into his field any point in a plane perpendicular to the axis of
the telescope. The optical characteristics of the instruments are as
follows:

  Power = 4.
  Field of view = 10°.

=The rotating head prism= has a movement of 600 mils in a vertical
plane; movement is obtained by turning elevation micrometer. The amount
and direction of rotation is indicated on a scale in the head by the
elevation index and micrometer. The scale is graduated in 100-mil
intervals, the micrometer in mils. One complete turn of the micrometer
is equivalent to one space on the sale. The head is level when the
index is opposite 3 and micrometer at zero.

[Illustration: PANORAMIC SIGHT MODEL OF 1917]

Movement in azimuth is obtained by turning =azimuth worm=. The
amount of rotation is read from the scale on the azimuth circle
and the azimuth micrometer. =The azimuth micrometer= may be turned
independently of the azimuth worm to set any desired deflection.
Figures in black are for right-hand deflection and in red for left-hand
deflection. The scale on the azimuth circle is graduated in 100-mil
divisions from 0 to 32 in each half circle. The micrometer is graduated
for every mil. For larger angular deflections, by turning the
throw-out lever the azimuth worm is disengaged, permitting the head to
be turned to any desired position.

=The reticule= is provided with a horizontal and a vertical cross line.
The horizontal line is graduated in mils.

=An open sight= attached to the side of the rotating head is for
approximate setting of the instrument.

No disassembling or adjustment of the panoramic sight, except as
described herein, is to be made, except by ordnance personnel detailed
for such work.

The panoramic sight is seated in a T slot in a socket of the sight,
model of 1916, in firing, and is carried in a panoramic sight case on
the shield when traveling.


Use of the Panoramic Sight for Direct Fire.

Level rocker with zero on range scale opposite 300 on angle-of-site
scale and gun at center of traverse. Set azimuth scale at zero, azimuth
micrometer knob at zero, micrometer index at zero, elevation scale at
3, and elevation micrometer knob at zero. By means of cross-leveling
knob on sight socket bring cross-level bubble level.

Correct for deflection in azimuth by turning azimuth micrometer
until required deflection is opposite fixed arrow pointer; bring
zero on micrometer index to zero on azimuth micrometer by means of
micrometer-index knob.

Elevate gun by means of angle-of-site handwheel and traverse until
cross hairs of panoramic sight are on target.


For Indirect Fire.

Level rocker and set scales for zero setting as directed in first
paragraph under “direct fire.”

Lay off required deflection in azimuth by means of micrometer index
and azimuth worm knob, so that deflection may be read from azimuth
index and azimuth micrometer. Traverse gun until vertical cross hair of
panoramic sight is on aiming point.

Vertical angles may be read by means of elevation scale and micrometer
scale. Zero point of elevation scale is 3. Each division on elevation
scale represents 100 mils.

All scales are graduated in mils.

The open sight on side of rotating head is used to obtain preliminary
direction of sight.

In turning azimuth angles greater than 100 mils the throw-out lever
may be pressed and rotating head turned to nearest division in even
hundreds desired. Each unit on azimuth scale represents 100 mils.


Panoramic Sight, Model of 1915.

=The panoramic sight= is a vertical telescope so fitted with an optical
system of reflecting prisms and lenses that the gunner with his eye at
the fixed eyepiece in a horizontal position can bring into the field of
view an object situated at any point in a plane perpendicular to the
axis of the telescope.

The rays coming from the object are reflected downward from the
rotating head prism into the rotating prism. The rotating prism
rectifies the rays; after their passage through the achromatic
objective lens, the lower reflecting prism reflects them in such a way
that there is presented to the eyepiece a rectified image, which the
eyepiece magnifies. A glass reticule marked with graduated cross lines
is located in the focal plane of the instrument, with the intersection
of the cross lines coincident.

The instrument has a universal focus, =a magnifying power of 4= and
=field of view of 180 mils=.

[Illustration: _PANORAMIC SIGHT MODEL OF 1915_]

The principal parts of the panoramic sight are the rotating head,
the elevation device and its micrometer, the azimuth mechanism with
limb and micrometer, the rotating prism mechanism, the deflection
mechanism, R and L scale and micrometer, the shank and the eyepiece.

The limb or azimuth scale is divided into 64 parts, each division
representing 100 mils.

The azimuth micrometer is divided in 100 equal divisions or mils,
numbered every 5 mils. One complete revolution of the azimuth
micrometer is equal to the distance between divisions on the azimuth
scale. The limb of the deflection scale is divided into six divisions;
three on each side of the zero, red for right and black for left, each
division representing 100 mils. The deflection micrometer, engraved
upon the front end, is graduated into 100 equal divisions, numbered
every 10 mils, red and black in opposite directions.


THE RANGE QUADRANT

The range quadrant consists of the quadrant spring fastening and
bracket, rocker, body, scroll gear, range disk, range and cross levels
with suitable leveling screws, and a micrometer to set off the angle of
site.

The range disk is graduated to 6500 yards, least reading every 50
yards, scale numbered every 500 yards. This disk is operated by a
scroll gear. Large changes in range may be made by pulling out the
handwheel, thus disengaging the scroll gear, and moving the body and
index to the approximate range, whereupon the handwheel is released,
and the range accurately set by again turning the handwheel.

The micrometer has 100 divisions and is operated by a milled head. The
limb of the micrometer, called the level scale, is graduated from 2
to 5, each division corresponding to one complete revolution of the
micrometer. The arbitrary reference point or mean position of the level
holder is 300 which corresponds to a point on the same level as the
gun.

[Illustration: _RANGE QUADRANT_

  _REVISED JUNE 4, 1908, JULY 30, 1910, FEB 6, 1911._
  _CLASS 36-DIVISION 22 DRAWING 5_
]


CARE AND INSPECTION OF SIGHTS.

=Rear sight Bracket.=—Should not be bent, broken or cracked. Must be
seated firmly in the bracket support.

=Shank Socket Mechanism.=—Not bent or burred; interior of shank socket,
scroll and worm gears free of scratches, burrs or deformed threads.
Sight shank easily inserted and moved up and down in the socket.
Scroll gear securely held in mesh with rack of sight shank. For large
movements of shank, should be easily disengaged by pulling out scroll
gear handle; must be securely held in place by spring when released.
Keep interior well lubricated. See that level vials of cross and
elevation levels are intact and bubbles not too large.

=Sight Shank.=—Rack on right side must engage with scroll gear; keep
lightly oiled. Sight shank should remain in fixed position except when
disengaged or operated by scroll gear handles. For changes in range
of 300 yards or less use only the scroll gear; over 300 yards pull
scroll gear handle and slide shank up or down in socket by hand, making
accurate setting with the scroll gear.

=Panoramic Sight.=—Lug must fit snugly in T slot of rear sight and
then held fast by clamp screw and ratchet. When making ready for march
order, first set the azimuth and R & L deflection scales at zero,
and the elevation scale at 300. Release clamp screw and ratchet. In
removing panoramic sight, grasp at center below the azimuth gear case,
lift vertically out of the socket, lower the top of sight to the left
and replace in panoramic sight box.

=Quadrant.=—Must fit snugly in its bracket, spring catch engaging. Nut
on range disk must be tight to prevent slipping. To remove quadrant,
press on spring catch before sliding off bracket.

=The sights= are correctly adjusted when, at zero elevation and
deflection, correction having also been made for difference of level of
wheels, the line of sight is parallel to the axis of the bore.

The =range quadrant= is correctly adjusted when, with the range disk
set at zero, level set at 300, axis of gun horizontal and corrected
for difference of level of wheels, the bubble of the range level is
centered.

In adjusting sights, the panoramic sight should _first_ be corrected.
If the rear sight is adjusted first, it will require readjustment if
the subsequent adjustment of the panoramic sight causes a change in
position of the rear-sight range strip.

=To adjust the panoramic sight.=—Select a well defined point at least
2000 yards distant. If the bore sights are not available, stretch two
threads or hairs from the tail of a horse across the grooves marked
on the face of the muzzle and fasten them by a strap or rubber band.
Remove the firing-lock case from the hub of the block-carrier. By
sighting through the hole in the vent bushing of the breechblock,
adjust the intersection of the cross hairs on the distant point, using
the elevating and traversing mechanisms of the gun. Now without moving
the gun or disturbing the laying of the cross hairs, bring the cross
wires of the panoramic sight on the same distant point by means of the
azimuth scale worm-knob and the scroll gear of the rear sight (_on
panoramic sights_, M1915, _to the deflection R & L scale should first
be made to read 0, and the elevation scale of the objective to read
300_). The cross hairs of the gun and the cross wires of the panoramic
sight will thus be laid on the same point. Now adjust the azimuth
micrometer scale to read 0 by means of unscrewing and tightening the
screw on the milled head. Loosen the nut on the range strip; move it
up or down until it reads (0) 100. Tighten the nut again. Verify the
laying. For this adjustment, it is not necessary to have the wheels or
the carriage on a level platform; cross level should be leveled.

=To adjust the rear sight.=—Having adjusted the panoramic sight and
the rear sight range strip as described above, and without disturbing
the laying of the gun, shift the deflection scale of the peep sight
and raise or lower the front sight until the cross wires of the latter
are laid upon the same distant point. Now loosen the two screws of the
deflection scale and place the 0 of this scale opposite the index of
the peep sight. The front sight is raised or lowered by removing the
split pins and then turning the front sight in the sight bracket sleeve
either up or down.

=To adjust the quadrant.=—(a) If an adjusted B. C. telescope or another
gun with its quadrant in proper adjustment is available, the angle of
site of some distinctly visible and distant point is measured by either
of these means. The gun to be adjusted is then laid upon this distant
point either with the bore sights, or with the tangent sight set at 0
(or some other convenient) range. The measured angle of site is then
set off on the level scale of the quadrant and the bubble of the range
level is centered by turning the handwheel of the range disk. By using
the quadrant wrench, the range disk is then adjusted to read 0 range,
(or the convenient range previously set off on the tangent sight).

(b) If no means are at hand to correctly measure the angle of site of
a distant point, the quadrants may be adjusted by using two guns as
follows: Unlimber two guns at about the same level, first seeing that
the sights are in adjustment (par. 75). Lay both guns upon some distant
point by means of the panoramic sight set at 0 range. Now set both
quadrants for the same angle of site (roughly estimated A. S. of the
distant point) and center the bubbles of the range level by turning
the handwheel of the range disks. By means of the quadrant wrench,
adjust the range disk of one of the quadrants to agree with the other.
Whatever error exists will now be the same in each quadrant.

Now move one of the guns about 100 yards away and turn the muzzles
toward each other. With the sights set at 0 range, lay the panoramic
sights upon each other and measure the angle of site of each gun. Half
the difference of the two readings will be the slope of the line of
sight between the two guns. On the level scale of the quadrant which
read the greater angle of site, set off 300 plus the half-difference,
on the other quadrant set off 300 minus the half-difference. Now
center the bubble of the range level by turning the handwheel of the
range disk. By using the quadrant wrench, adjust the range disk until
it reads 0 range. Having thus adjusted two guns, the others may be
adjusted by the first means described.


OBSERVING INSTRUMENTS.


B. C. Telescope, M. 1915.

=The B. C. Telescope, M. 1915=, is a binocular observing instrument
of the scissors type. The two tubes of the telescope may be clamped
either in a vertical or a horizontal position. In the former position
the objectives are 12 inches above the eyes of the observer, and in the
latter position they are 24 inches apart and at the same height as the
eyes of the observer. In both cases they permit the observer to take
advantage of some shield or other cover and still obtain a full view of
the sector of observation. The tubes may be adjusted for the observer’s
interpupillary distance in either the vertical or the horizontal
position. The eyepieces may be adjusted to the eyes of the observer by
screwing in or out.

[Illustration: _BATTERY COMMANDER’S TELESCOPE MODEL OF 1915._

  _36-22-31_
]

=The principal parts of the telescope are=:—Leveling mechanism,
azimuth mechanism, elevating mechanism, angle of site mechanism, the
telescopes and the tripod. A carrying case is provided separately for
the instrument and for the tripod. In garrison a storage case is also
provided.

_The leveling mechanism_ consists of a ball and socket joint operated
by the vertical spindle clamping screw.

_The azimuth mechanism_ consists of the azimuth worm knob with its
lever, operating the azimuth worm and worm wheel; the adjusting or slow
motion knob and the azimuth clamp. The azimuth limb is divided into
64 parts, each division representing 100 mils. The azimuth micrometer
is divided into 100 equal parts or mils, numbered every 10 mils. One
complete revolution of the micrometer is equal to one division of the
limb. The scales therefore correspond to those on the panoramic sight,
6400 mils to the circumference.

The leveling mechanism is operated by the small elevation worm knob.

_The angle of site mechanism_ consists of the level, the angle of site
scale and micrometer with its worm knob.

_The telescopes_ consist of the eyepieces, telescopic tubes with their
optical systems. In the right eyepiece is a graduated cross wire which
can be rotated for either the horizontal or the vertical position.

_The tripod_ is similar to the usual telescopic instrument tripod.

The optical characteristics of the instrument are as follows:—Power
10; field of view 75 mils; focal length of objectives 11½ inches; the
field is flat, free from chromatic and sphercial aberration, coma and
distortion.


Care and Instructions.

=To set up the telescope.=—First set up the tripod, clamping and
propping the legs so as to obtain the desired cover and view. By means
of the vertical spindle clamping lever, approximately center level on
azimuth worm case and clamp tightly. Carefully take out B. C. telescope
from case and while pressing on locker plunger, place telescope on
vertical spindle so that the projection on the azimuth worm case will
fit into the corresponding slotted segment of the telescope. Release
the locking plunger.

=To focus the eye pieces.=—Adjust each eye piece separately by turning
the same until the image of a distant object appears sharply defined.
Read the diopter scale, plus or minus, and note for future use.

=To adjust the interpupillary distance.=—The eye pieces having been
focussed, loosen the large friction clamp knob in front. Grasp both
tubes with the hands and separate or close them in (either in the
vertical or horizontal position) until the fields of view of the two
eye pieces are exactly coincident and present a single image to the
eyes. This can be tested by alternately closing one eye and then the
other, noting any movement in the image. Tighten the large friction
clamp knob. Read the interpupillary scale and note for future use.

=To lay 0 on any point.=—Level the instrument by means of the vertical
spindle clamping screw. Bubble must remain approximately centered while
instrument is turned 1600 mils. Set both the azimuth index and the
micrometer to read zero. Release the azimuth clamp shaft knob; turn the
telescope toward the point and tighten the azimuth clamp shaft knob.
Bring the vertical wire accurately on the point by turning the azimuth
adjusting worm knob.

=To measure the deflection and site of a target.=—Lay the zero on the
aiming point as above. If the line of sight must be moved through a
large angle, press down the azimuth worm lever as far as it will go
and while holding it down move the azimuth mechanism until the line of
sight is approximately directed upon the target; then release the worm
lever and bring the cross wires accurately on the target by turning the
azimuth worm knob (for deflection) and the elevation worm knob (for
elevation). Center the site level. Read the deflection and site.

For carrying the B. C. telescope assembled on the tripod, clamp tightly
the vertical spindle clamping lever; close in and clamp the tubes of
the telescope; slide up and clamp the lower tripod legs; then carry the
telescope over the shoulder by grasping the tripod legs, tube bases of
telescope resting on the shoulder.

=To dismount the B. C. Telescope and to pack in carrying case.=—Screw
in both eye pieces. Press on the locking plunger and lift the telescope
vertically off the spindle. Unclamp the large friction clamp knob,
bringing the tubes together and insert in the carrying case; close and
lock the lid. In dismounting the tripod the leg separators of the upper
sections should first be unclamped. After the lower legs have been
assembled, they should be clamped. To set up the tripod the operation
is reversed.


Aiming Circle, M, 1916.

=The Aiming Circle= is an angle measuring instrument only and consists
of a telescope, leveling mechanism, angle of site device, elevating
mechanism, azimuth circle and compass, mounted on a tripod.

Its leveling, azimuth and angle of site mechanisms are similar to those
in the B. C. Telescope, as is also the tripod. The elevating mechanism
consists of elevating worm knob and gear connecting it with the
telescope. The telescope has a universal focus, magnifying power of 4,
and a field of 180 mils. The cross wires are illuminated by a window.
The compass is secured by the needle release button.


Care and Instructions.

Glass compass cover should fit tightly. Compass needle when clamped
should not rotate while instrument is revolved or tipped. When
release button is pressed, compass must swing freely on pivot and again
remain clamped when button is released. _Compass should be released
only when aiming circle is set up and horizontal._

[Illustration: AIMING CIRCLE

  _36-22-30_
]

Bubble must remain approximately centered while instrument is turned
1600 mils.

=To lay 0 on any point.=—Set both the azimuth index and the micrometer
to read zero. Release the wing nut; turn the telescope toward the point
and again tighten the wing nut. Bring the vertical wire accurately on
the point by turning the adjusting worm wheel.

=To measure the deflection and site of a target.=—Lay 0 on the aiming
point as above. If the line of sight must be moved through a large
angle, press down on the azimuth worm lever as far as it will go and
while holding it down, move the azimuth mechanism until the line of
sight is approximately directed upon the target; then release the worm
knob (for deflection) and the elevation worm knob (for elevation).
Center the site level. Read the deflection and site.

=To measure the compass deflection of a target.=—Set both the azimuth
index micrometer to read 40. Release the wing nut; turn the telescope
until the N and S poles of the compass are respectively near the N and
S points marked on the compass box. Make the coincidence accurately
with the adjusting worm wheel. Now proceed to measure the deflection
and site of the target as described above.

=The Tripod and Azimuth Gear Case.=—The leather cover protecting the
ball and socket joint must fit snugly both above and below, and be free
of rips or holes. The ball and socket joint and the tripod legs should
be easily adjusted and moved, but should remain fixed when clamped by
the clamping levers.

For carrying the aiming circle assembled on the tripod, the wing nut
and the vertical spindle clamping lever should be clamped tightly and
the instrument carried over the shoulder by grasping the tripod legs,
head of tripod resting on the shoulder.


Adjustments B. C. Telescope and Aiming Circle.

The B. C. Telescope and the Aiming Circle are correctly adjusted when
the following conditions prevail: Telescope properly focussed; plane
of level perpendicular to the vertical axis of the instrument; angle
of site scale reading 300 when the line of sight is horizontal; lost
motion on worm gears eliminated. In principle, the adjustments of
the B. C. Telescope and of the Aiming Circle are exactly the same.
The leveling and focusing have already been described. Detailed
instructions of the operations in eliminating lost motion in the worm
gears will be found in the _Handbook for F. A. Fire Control Equipment_,
1916.

=To make the site scale read 300 when the line of sight is
horizontal.=—Set up the telescope or aiming circle. Level the
instrument so that the bubble on the azimuth worm case will remain
centered while the instrument is turned 1600 mils. Lay on some point
of a stake or other vertical linear object which is at a convenient
distance but not closer than 100 yards to the instrument. The point
selected should be at such a height that the telescope can later be set
up close to it, with the objective at the same height as the selected
point. Read the angle of site. This reading will be equal to (300 + S
+ E), in which S is the angle of slope of the line of sight, and E is
the error in the site adjustment. Before leaving this station, set up a
second stake near the telescope and mark on it a point which is at the
height of the objective.

Now move the telescope to the first stake; set up and level the
instrument with the objective at the height of the point marked on this
stake. Lay on the marked point of the second stake and read the site.
This angle will be equal to (300 -S × E). Subtracting one reading from
the other we have:—(300 × S × E) - (300 - S × E) = 2S; or one-half the
difference of the two readings is equal to the angle of slope of the
line of sight. Therefore with the cross wires directed upon the marked
point of the second stake, center the bubble of the site level. Now
loosen the angle of site locking screw and turn the micrometer to read
(300 - S), being careful to keep the bubble centered. Screw up the
locking screw. The instrument is now in adjustment.

After one telescope has been adjusted, other telescopes, aiming circles
and quadrants may be adjusted by merely measuring the site of some
distant point. The other telescopes and guns, being in position near
the adjusted telescope, are then made to read the proper site when laid
upon the distant point.


FIELD ARTILLERY RANGE FINDER, 1 METER BASE

(Bausch & Lomb.)

The instrument and accessories consist of the range finder proper, the
tripod mount, the tripod, the adjusting bar, the carrying-case and the
storage box.

The optical parts of the =range finder= are embodied in a seamless,
steel tube (A) covered with canvas and asbestos, to minimize the
effects of the change of temperature. The eyepiece (B) is located in
the center of the instrument and is equipped with a focusing device
graduated in diopters. A soft rubber eye cap is furnished to protect
the observer’s eye from shocks and stray light. A ray filter having two
sets of glass is operated by a small lever (C) situated to the lower
left of the eyepiece housing.

[Illustration: _DIAGRAM TO ILLUSTRATE THE GENERAL PRINCIPLE OF
RANGE-FINDERS._]

The objective openings on the end boxes are opened and closed by means
of rotating shutters (D). Buffers (E) are provided on the ends as a
protection against shocks.

The range finder is of the type known as the fixed base, invert, single
coincidence. The magnifying power is 15; actual field of view 50 mils;
shortest distance measurable 400 yards. The instrument weighs about
20 pounds. Under favorable conditions and with expert operators the
average errors are:

  1000 yds.      5 yds.
  2000 yds.     15 yds.
  3000 yds.     30 yds.
  4000 yds.     55 yds.
  5000 yds.     90 yds.
  6000 yds.    130 yds.
  7000 yds.    175 yds.
  8000 yds.    225 yds.

In practical use under ordinary conditions and with average operators,
the errors are three times as great.

=The tripod= mount consists of a spring catch (a); clamping lever (N);
elevation worm case (b); elevation worm knob (c); worm wheel support
(d); angle of site micrometer (e); angle of site housing (f); angle
of site vial holder (g); clamp screw handle (h); azimuth worm knob
(i); azimuth micrometer (j); azimuth worm lever (k); azimuth scale
(m); adjusting worm knob (n); and the vertical spindle clamping lever
(p). The tripod, consisting of spindle bushing locking screws (t);
tripod legs upper (r); tripod legs lower (q); clamping wing nuts (w);
and locking clamp arms (x), is similar to that provided for the B. C.
telescope and the aiming circle.


Care and Instructions.

=To set up the Range Finder.=—Set up the tripod as heretofore
prescribed, take the range finder from its case, holding it with
the eye piece toward the body, hook down. Place the instrument on the
support and engage the spring catch (a). The instrument is then firmly
seated on the tripod. Remove the protective hood from the eye piece
and the rotating shutters (D) from the objective apertures. Loosen
the locking lever so that the range finder may be made horizontal,
then turn toward the target and clamp the lever. To dismount the range
finder the operations are executed in an inverse manner.

[Illustration: REAR VIEW RANGE FINDER.]

[Illustration: RANGE FINDER.]

=To Measure a Distance.=—Focus the eye piece. In very bright light or
in thick haze use the amber ray filter in the eye piece. By means of
the clamps and worm knobs of the azimuth mechanism and the worm knob
of the elevation mechanism, lay the range finder on the target roughly
by looking through the open sight on top of the instrument. Final
adjustment in deflection is made by the adjusting worm knob (n) and in
elevation by the elevation worm knob (c).

Now, look into the instrument. The field of view is divided into two
parts by a horizontal line. In the lower part the image is erect, in
the upper part inverted. By turning the elevation worm knob (c), the
images are lined up so that the same points will touch the dividing
line. Now, by turning the measuring roller (M) on the right hand top
side of the range finder, the upper image is shifted laterally until
the same vertically disposed points of the target are exactly opposite
each other. The range is then read on the range scale (H), which is
protected by a sliding shutter (Q).

In case the target is without prominent vertical features, such as a
crest line, the distance is measured by first turning the instrument to
a vertical position (Plate XV). This is accomplished by the clamp screw
handle (h) on the tripod mount. Final adjustment in deflection is then
made by the elevation worm knob (c), and in elevation by the clamping
lever (N).


Adjustments.

=Adjustment for Height.=—The erect and invert images sometimes do not
touch the dividing line with similar point so that one image reaches
this line before the other. In this case, lay the range finder on an
object having a sharply defined horizontal line or very prominent
point, and bring the images of this point exactly opposite each other
by means of the measuring roller (M). The two images are then brought
to the dividing line, the lower image by means of the elevation worm
knob (c), and the upper image by means of the halving adjusting roller
(J).

=Adjustment for Range.=—Three methods are available for adjusting the
range finder for range; the artificial infinity method, using the
adjusting bar; the actual infinity method using the sun, moon, star, or
a very prominent distant point; the known range method, using a point
the range to which is known. Of the three, the first is the best and
should habitually be used.

=By the Adjusting Bar.=—Set up the range finder; take the adjusting bar
and place it 100 yards from the instrument, sighting through the peep
sight (y) of the adjusting bar and moving it until the range finder
appears in the center of the field of view. Set the range scale at
infinity by turning the measuring roller (M), then make an observation
on the adjusting bar. The right hand line of the upper image of the
adjusting bar and the left hand line of the lower image should now be
coincident, in which case the instrument is in adjustment (Fig. 10).
If not, bring these lines in coincidence by turning the key which fits
the square shaft (K), which operates the range correction dial (L).
This operation should be repeated at least three times, the reading of
the range correction dial being noted each time. Now, set the range
correction dial at the mean of the three readings. Remove the key.
The instrument is now in adjustment. Before using, always note the
reading of the range correction dial.

[Illustration: THREE STEPS IN MEASURING A DISTANCE.]

=By the Actual Infinity Method.=—This method is in all respects the
same as the one with the adjusting bar, except for the images. After
the instrument is set for infinity, actual coincidence is made as in
paragraph 99.

=By the Known Range Method.=—Operate the measuring roller (M) until
the range dial reads the actual distance to the object. After the
range finder has been set for this known range, actual coincidence is
obtained by using the key which operates the range correction dial.


FIELD GLASSES.

The instruments for focusing the eyepieces and for adjusting the
interpupillary distance are the same as for the telescope.

The two barrels should revolve easily about the central pivot and clamp
in any position of the interpupillary scale.

After being once adjusted, the field glasses should fit into the case
without being changed.

Carrying strap, button strap and rain shield should always be part of
the equipment. Amber shades and camels hair brush should be carried in
the case for use.

The vertical scale in the Type EE Field Glass represents the Infantry
range scale and does not apply to Field Artillery.

Compass should always be securely clamped except when in use.


THE BRACKET FUZE SETTER, MODEL 1905 M.

The bracket fuze setter is attached to the rear end of the fuze setter
bracket on the caisson. It consists of the following principal parts:
Base, housing, corrector-worm case, guide, range and corrector worms,
rings, and scales.

The corrector scale reads from 0 to 60, numbered every 10 points, 30
being the normal or mean arbitrary point. The range ring is graduated
to 6400 yards, numbered every 500 yards, least reading 50 yards. These
rings are graduated for the F. A. fuze on one side and for the Ehrhardt
fuze on the other. Care should be taken that the proper side is up when
firing the two different kinds of shrapnel.


THE HAND FUZE SETTER, MODEL 1912.

The hand fuze setter is provided for the same purpose as the bracket
fuze setter, and is intended to supplement the latter. One hand fuze
setter is issued in a leather case and is carried in the trail box of
each gun. It is intended for the use in case the bracket fuze setter
should become disabled, or in case the gun should for any reason be
separated from its caissons. The principal parts are the case, the
range index mechanism, range mechanism, corrector mechanism, and guide
plate.

[Illustration: _HAND FUZE SETTER, MOD. OF 1912_]




CHAPTER XV

SIGNAL EQUIPMENT.


CLASSIFICATION.

The most important and widely used means of communication used by
artillery with their advantages and disadvantages follow:

=(a) Telephone.= The telephone is the quickest and most satisfactory
means of communication, and is the most generally used of all means.
Near the front, in areas subjected to fire it is often difficult to
maintain lines and unless a line be a very carefully insulated and
transposed metallic circuit, conversations held over it are picked
up by the enemy listening service. To guard against such information
being of value to him, telephone codes have been devised, for use in
important messages.

=(b) Radio.= Radio provides a reasonably certain means of
communication, but such messages are always intercepted by the enemy.
Its use requires enciphered messages.

=(c) Projectors.= Projectors afford a very reliable means of
communication, but their use depends, to a great extent, on atmospheric
conditions, and frequently they may not be used from rear to front and
are slow in operation.

=(d) Flags.= Semaphore and wig-wag prove fairly satisfactory only on
exceptionally favorable conditions and in open warfare.

=(e) Runners.= Used as a last resort. Slow and wasteful but usually
reliable.

In each battalion (F. A.) there are a radio officer, telephone officer,
and enlisted personnel for the maintenance of the communication system.


The Camp Telephone.

This telephone, which supersedes the field telephone, was developed
by the Signal Corps for use in connection with camp telephone systems
and small arms target range systems, and may be installed in tents
and structures, or considered a portable instrument for use in the
field for testing lines or other purposes. It is of local battery
type. The battery employed is one unit of Tungston Type A which is
made up of two small cells so placed in a rigid paper that they are
connected in series. The combination gives a total voltage of 3—1½
being normal voltage of each cell. The instrument is made as compact
as practicable and is contained in an oak case 4¼ × 7 × 10” high. The
top consists of a metal hinged cover with circuit diagram on inside,
held rigid when closed by a spring snap which can be readily released
by depressing a button. The bottom of the case is covered by a flanged
piece of metal, the flange projecting approximately one-half inch up
sides of case. Through one side of the case are six three-eighths inch
holes which are covered on the outside by a close mesh metal screen
held in place by a metal frame. These apertures are for the purpose
of allowing the ringer to be distinctly heard. The case is equipped
with a substantial, adjustable carrying strap, each end of which is
fastened to the case by means of hinged metal rings. A small 3-bar
magneto generator, small ringer, induction coil, aluminum chamber for
the single unit of tungston Type A dry battery, hard rubber block
upon which are mounted line binding posts, plug connections for the
handset used with the instrument, hook switch and hook operating it and
auxiliary battery binding posts, are all mounted on a common base which
may be readily removed from case after removing magneto generator
crank, metal housing for it and three screws which extend through
the case. The instrument may be operated with cover closed which is
highly advantageous in inclement weather. To accomplish this there is
a suitable opening for leading out the 3-conductor cord to receiver
and transmitter, the two latter being mounted in the form of a unit,
termed a handset. This handset consists of a transmitter and a receiver
mounted on a metal piece and is so designed that when the transmitter
is normally placed to the mouth, the receiver is automatically adjusted
to the ear. The hook of hook switch is so designed that it protrudes
through the case. When it is desired to transport the instrument or to
remove the base upon which is mounted all parts of the instrument, it
is merely necessary to depress the hook and push it toward the base. By
this arrangement the hook is not only held in the down position thereby
opening the battery circuit, but it is also protected. The aluminum
chamber for housing the single unit of tungston type A battery is
equipped with a spring catch so located that when upper hinged piece is
depressed to proper position, the battery compresses a helical spring,
thereby insuring continual contact. The base is equipped with two
screw binding posts which may be used to connect leads to an outside
battery in the event of there being no tungston type A batteries
available. An aluminum frame which is supported on the base previously
mentioned forms a compartment for the handset when instrument is being
transported. When the instrument is installed for a temporary period,
unless in actual operation, the proper place for the handset is hanging
on hook of hook switch, there being a ring on the handset for this
purpose. A small screwdriver which will fit practically all the screws
used in the construction of the instrument is supported by the metal
frame and is furnished with each instrument. The instrument complete
weighs about 11 pounds.

[Illustration: THE CAMP TELEPHONE.]

[Illustration: CAMP TELEPHONE WIRING.]


The Monocord Switchboard.

The liaison of telephone intercommunication between army units is
frequently such that a temporary, quickly installed and flexible
type of small central exchange located in the field, is essential.
Such an exchange is usually placed in a well protected dugout at the
infantry battalion headquarters, artillery battalion headquarters,
central artillery observation post, etc., where it will be the central
terminal point of from four to twelve or more lines connecting with the
headquarters of the higher command, with the several units working with
the battalion, and with the joining similar battalions. The switchboard
which has been designed to meet these requirements is called the
“monocord switchboard” and is made up of either four, eight or twelve
of the type EE-2 switchboard units.

The monocord switchboard is made up of unit panels, on each of which is
mounted all the apparatus needed for the central exchange end of one
telephone line. These panels are made of insulating material and are
mounted in special wooden frames in groups of four, eight and twelve
units, according to the size of the installation necessary. The two
sizes most commonly used in overseas work are the four unit and twelve
unit boards. Each unit is removable from the frame, thereby lending
flexibility to the board and facilitating repair and replacement.
Generally, this type of board is used only for a small number of lines
as the operating facilities do not permit speedy connections, and it
is always better practice to use only three lines on a four unit board
and 11 lines on a twelve unit board in order to have a spare unit
immediately available.

The monocord switchboard may be used with either a magneto telephone,
camp telephone, field telephone Model 1917, buzzerphone or service
buzzer. The operator’s telephone set is not furnished as a part of
the switchboard and a separate telephone set of one type previously
mentioned must be supplied for this purpose.

=Switchboard Frame.=—The switchboard frame is made of hard wood,
varnished in order to make it moisture proof. Its function is to hold
the various units together and to protect them from dust and mechanical
injury. In the back of the frame there are three horizontal brass bars
extending the width of the board. In addition to providing a mechanical
support for the various units, the top bar serves as a common ground
connection and the middle and bottom bars as common night bell and
battery connections for all units. Three Fahnestock clips on American
made boards and binding posts on French made boards are installed at
the top of the frame and four at the bottom. On the French made boards
the upper three binding posts are marked S1, S2 and T, and are used
for connecting by independent wires, respectively, the night bell and
ground. The two posts at the bottom of the frame marked ZS and CS are
used for connecting the two poles of the night bell battery. To the
other two marked P1 and P2 are connected the operators telephone and
the operators plug. The terminals at the top of the American made
boards are marked A, A1 and G, corresponding with the French S1, S2 and
T, and those at the bottom are marked B, B1, L1 and L2, corresponding
to ZS, CS, P1 and P2, respectively.

If two or more multi-unit boards are connected in parallel for
operation at one exchange, the interconnections between boards in
order to use one ground, one night bell and one battery for the whole
exchange are made. The corresponding binding posts at the top and
bottom of the frames are simply connected to each other, as S1 and S2
of No. 1 board to S1 and S2, respectively, of No. 2 board.

=Unit Panel.=—Each unit comprises all the necessary apparatus for the
exchange terminals of one line (two wires). The various parts are
listed below according to their position on the panel from top to
bottom:

  Two connecting blocks for the line wires.
  Lightning arrester between these blocks.
  Two fuses.
  Line number plate.
  Line drop signal and night bell contact.
  Jack.
  Cord and line plug.

Each unit is held in the frame by means of two machine screws, one at
the top and one at the bottom of the unit, which engages the brass bars
in back of the board and hold the unit firmly in place. Rigidity of
construction is essential, as constant use and transferring from one
place to another tend to loosen the units from the frame and disturb
the sensitiveness of the adjustment of the line drop.

=Lightning Arrester.=—The lightning arrester is a simple toothed
washer held against the panel by the supporting screw. This screw is
grounded through the upper brass bar. If lightning comes in on the line
wires, the main portion of it jumps the small air gap from the binding
post to the grounded washer and thence passes to the ground, so that
only a small portion of the high frequency current flows through the
switchboard apparatus. If the latter portion is at all heavy, the
fuses burn out, opening the circuit through the switchboard with a much
wider gap, and hence higher resistance than that in the circuit to
ground across the arrester.

=Line Fuses.=—Two glass enclosed removable fuses, which fit into
spring connections, are provided to protect each side of the line from
excessive currents. In order that burned out fuses may be readily
seen, the panel is painted white behind them. The glass is usually
smoked up more or less when a fuse burns out and this against the white
background is easily noticed.

=Line Number Plate.=—The line number plate is a small white celluloid
strip on which the line number is written. This number may easily be
erased if it is necessary to change it.

=Line Drop Signal.=—The line drop signal consists of a shutter held
normally in a vertical position by a brass trip latch. This trip
latch is attached to the armature of a small electromagnet which is
normally connected across the line through the anvil and the jack tip
contact spring of the switchboard jack. When the coils of the magnet
are energized by a current sent over the wire from a calling station,
the armature and trip latch are lifted, thereby releasing the shutter,
which falls by gravity to a horizontal position and attracts the
attention of the operator. The electromagnet is adjusted to operate on
a very small current. For locking the shutter in the vertical position
and protecting it from mechanical injury during transport, a flat
spring lever is provided which may be turned up from a pivot at one end
to press against the shutter.

=Night Bell Spring Contact.=—The night bell contact is located in
the back of the panel. The battery and bell circuit through this
contact is closed when the line signal drop shutter is released by the
electromagnet, this forcing the spring back against the contact point.
The night bell spring contact consists of a narrow flat brass spring,
screwed at one end to the drop mounting plate. The contact point is
mounted on the back of the panel, the rear end of this rod making
contact with the night bell bus bar, against which the rod presses
when the panel is screwed in place on the bars along the back of the
switchboard.

=Switchboard Jack and Line Plug.=—Each unit is provided with a jack
and plug. The jack consists of a cylindrical opening in the panel of
the unit, behind which are arranged the tip contact spring, the sleeve
contact spring and the anvil. The tip spring is connected through one
of the fuses to one of the line wires. The anvil is connected to the
other line wire through the electromagnet coils and the other fuse.
The magnet circuit is normally closed across the line when there is no
plug in the jack, as the tip spring and the anvil are then in contact.
A current coming in over the line, then, would energize the coil.
The sleeve spring of the jack is connected directly to the same line
wire as the anvil, the line plug is bridged across the tip and sleeve
contact spring. It is a standard two-contact type, the tip and the
sleeve making direct connection to the line.

=Operators Equipment.=—Any equipment which is not individual to a
line, but which is used in common to all lines in the process of
interconnection, is called the operator’s equipment. This consists
of an ordinary telephone set, employing either magneto or buzzer and
including a transmitter, receiver, induction coil, generator, battery
and connection, together with the wiring and the associate parts
necessary to co-ordinate them with the rest of the apparatus. An
operator’s equipment also includes a night bell and battery.

=Carrying Case.=—Carrying cases made of fiber and provided with
hand straps are furnished with monocord switchboards to provide a
convenient means of carrying them and to protect them from damage
during transportation. These cases are made so that they will hold not
only the frame with the assembled unit, but also the switchboard cords.
To move the board it is necessary to disconnect the night bell battery,
the night bell, the ground connection, the operator’s set and the
several line wires.

=Care and Adjustments.=—Care must be exercised when a board is
installed to make sure that the frame is in a vertical and level
position. When assembled at the factory, all adjustments are made
with the board in a vertical position and all operations conductive
to satisfactory service depends on this prerequisite being observed.
The line signals of the monocord switch boards are of the gravity type
and require careful adjustment. Any adjustment further than that done
at the factory should be made by an expert who is thoroughly familiar
with this work. During transportation and installation of this board,
the line drop shutters should be held closely by the flat springs
previously described. The burning out of a fuse when excessive current
comes in on a line that is detached by an open circuit on that line. A
bad fuse generally shows plainly against the white background on the
panel. However, if it is not possible to see whether or not the fuse
is burned out, the line may be short circuited momentarily by means
of a piece of bare copper wire placed across the two line terminals.
The operators is then inserted in the jack of the unit under test, and
the magneto crank turned. If the fuse is burned out, the crank will
turn over easy; if not, it will turn hard, indicating that the open
circuit is elsewhere on the line. A burned out fuse should be replaced
immediately in order to keep all lines working. Several spare fuses
should be kept on hand at all times but in case no fuse is available,
a strand of small copper wire may be connected across the upper and
lower fuse clips. To remove a fuse, take the bottom metal cap of the
fuse between the thumb and finger and push upward against the spring
holder on the line terminal block, at the same time pulling outward.
To install a fuse, hold it in the same manner and put the other end
of the fuse in the upper spring contact, forcing it upward until the
bottom ends slip into place. Care should be taken to keep the small
air gap between the toothed washer and the line terminal clean. If
this precaution is not taken, and the air gap is allowed to clog up
with dust and dirt, it will introduce a leak to ground or between
wires with resulting poor transmission. All mounting screws and all
wire connections should be kept tight. Whenever the unit is damaged,
it should be replaced by another one, the damaged unit being sent back
to headquarters for repair. In this connection it should be noted that
the American unit panels and parts have been made interchangeable with
the French to facilitate repair. To remove a unit from the frame, it is
only necessary to disconnect the line terminals and remove the top and
bottom screws which engage the brass bars behind the board. In handling
the switchboard cords, they should be grasped by the plug, not by the
cord. The connection of the wires to the tip and sleeve of a plug will
break, is subject to undue strain or abuse, and by taking hold of the
plug while inserting it and pulling it out, the likelihood of breaking
the internal connections and wearing out the wires will be reduced to a
minimum.


Disadvantages of the Monocord Switchboard.

1. It does not afford as quick connections as the by-cords switchboard
type.

2. It is not self-contained. A self-contained switchboard includes
operators, receiver and transmitter and ringing and night alarm
circuits.

3. The operator’s telephone is usually equipped with a hand set,
(receiver and transmitter) which leaves him with only one free hand for
making connections.

4. One switchboard is equipped with but one master, or operators cord,
this affords only one means of answering and calling.


Advantages of the Monocord Switchboard.

1. Small, compact, light weight.

2. Simple wiring.

3. Quickly installed.

4. Particularly suited for small central exchanges.

5. Units can be removed quickly, in case of trouble in interior
circuits. Any unit can be removed without disturbing other units.


Common Faults and Remedies of the Magneto Telephone.

The most common trouble in telephone instruments are due generally to
one of three causes. (1) Loose or dirty connections at the binding
posts of the instrument, at the binding posts of the batteries, or in
joints of the line wires, (2) exhausted, poor, or weak batteries, (3)
crossed, open, or defective wires. These troubles, of course, do not
include those arising from inferior or defective instruments. If the
connections are dirty, corroded or greasy, scrape the wires and clean
out the binding posts, then screw the wires firmly in place. If the
telephone does not then work properly, examine the batteries and see
whether they are run down or whether the zincs are eaten away. With
wet batteries, it may be possible that the water has evaporated; in
dry batteries, the zincs may be eaten through or the batteries may be
otherwise defective. The simplest way to test a battery is to try a new
battery, and see whether it will make the telephone work properly; if
it does, the trouble is with the old battery. If the trouble is present
after changing the battery, examine the line connections and the line
outside; if any loose connections are found, correct them at once. When
inspecting the line outside see that it does not touch anything except
the insulators, and that it is neither crossed nor broken. On grounded
lines—grounded lines are obsolete now in modern warfare on the account
of the many means of detecting and picking up messages now employed; in
fact the metallic circuit telephone lines are now used within a mile of
the front lines except for messages which would be of no value to the
enemy—examine the ground connections the first thing and see whether it
is in good condition, and if a plate is used see that it is in moist
ground. The frequent trouble with transmitters is the frying noise;
that is usually caused by induction or static electricity, and may also
be caused by loose connections.

  1. Open Line.            { Effect:  Cannot receive a call or get
                           {          central.
                           { Test:    Follow line with portable magneto
                           {   test set and ring; if central gets ring,
                           {   open is toward station or visa versa.

                           { Effect:  Can hear and receive central call
                           {   but cannot talk.
  2. Open Battery.         { Test:    Strap out primary winding or
                           {   transmitter with test receiver, and
                           {   leaving the receiver off the hook at
                           {   station, listen
  3. Open primary winding. {   in either for click while moving
                           {   switchhook up and down. If no noise be
                           {   heard, battery circuit must be open, and
                           {   circuit should be followed with test
  4. Open Transmitter.     {   receiver, which will click loud where
                           {   battery is found to be O. K.

                           { Effect: No signal will show at magneto
  5. Short Circuited       {   switchboard, and use of station
      Line.                {   instrument will be impaired and magneto
                           {   will turn hard.
  6. Wet or short Circuited{ Test: Open line and ring; if magneto still
      Instrum’t.           {   turns hard open connections one at a
                           {   time, where available throughout entire
                           {   winding until magneto turns freely.
                           { Effect: Other talking heard on the line
  7. Line crossed with     {   when the receiver is off the hook.
      another line.        { Test: Ring magneto and with central’s help
                           {   try to locate other party; then trace
                           {   line.
  8. Open secondary        {
      winding.             { Effect: Can ring and hear central ring but
  9. Open receiver.        {   cannot hear in receiver although can be
 10. Receiver diaphragm    {   heard.
      missing or badly     { Test: Strap test receiver across open part.
      dented.              {

                           { Effect: Can hear well but cannot be heard
 11. Weak battery Cells.   {   clearly.
                           { Test: Use ampere meter and see if each cell
                           {   be weak.

                           { Effect: Can talk and hear in receiver but
 12. Open Bell.            {   bell does not ring.
                           { Test: Strap bell coils out with test
                           {   receiver and listen in.

                           { Effect: Bell rings from central but does
 13. Open magneto Armature {   not ring when magneto handle is turned
      Winding.             {   nor can central be called.
                           { Test: Ring with another magneto or test
                           {   set.

 14. Slight Short Circuit  { Effect: Can ring operator but cannot hear
      (escape) to          {   nor be heard clearly.
      Ground.              { Test: Open line, one line at a time, and
                           {   follow circuit with test set. Escapes are
                           {   due to wires touching damp walls, metal
                           {   roof, or other grounded wire where
                           {   insulation has been rubbed off.


Signaling by Means of Lamps.

Visual signaling by means of the lamp has been found to be very
important and efficient. Experience has shown that during the first
hours of a battle, particularly in an advance, before it has been
possible to establish the telephone systems, the lamp has furnished
the most dependable means of communication both by day and night. Even
in stationary or trench warfare in sectors with well organized systems
of communication, the lamp is most serviceable in transmitting short
messages such as calling for a barrage, reinforcements, etc., for which
arbitrary signals are used. In fact, this method is more precise than
the use of rockets and more rapid than the telephone in transmitting
information covered by these arbitrary signals. For these reasons, all
important telephone lines near the front are paralleled by the lamp
system.

=Description of the Lamps.=—The signaling lamps are made in three
sizes called the 14, 24 and 35 centimeter lamps. These dimensions
indicate the diameter of the reflector. The 24 cm lamp consists of a
portable searchlight, similar in principal to an automobile headlight,
but equipped with a sighting or aiming tube on top, a hinged lid to
cover the glass reflector, and a two-wire cable used to connect the
batteries for operating the bulb. The battery comprises eight dry cells
in series, carried in two leather pouches, each holding four cells.
These pouches are attached to a leather belt supported by shoulder
straps. The belt has also an additional pouch in which three extra
lamp bulbs are carried. A brass push button which projects through this
pouch is used as a key in completing the battery and lamp circuit to
make signals of short and long flashes. Connection between the lamp
and battery is completed by the two wire cable and the plug and socket
connector. The complete apparatus, comprising the lamp and the belt
and three spare light bulbs and eight dry batteries, is furnished in
a wooden carrying case. The 14 cm lamp is similar to the 24 cm, but
smaller, using a battery of four dry cells and being slightly different
in the manner in which it is carried. The 14 cm lamps come three in a
wooden case with extra batteries and lamp bulbs. The 35 cm lamp is a
larger model of the 24 cm lamp, is not as readily portable and employs
a storage battery. it is used only for permanent installations.

=Method of Operation.= The lamp and battery circuit is completed by
means of the plug and socket connector. The lid covering the reflector
is then opened and the operator sights through the tube to locate the
station with which he is to communicate, and signals by means of the
push button key. It is essential that the lamp be held rigidly and the
sighting tube be continuously aimed exactly at the receiving station
during signaling. A slight movement of the lamp makes the signals
appear blurred or entirely invisible to the receiving station. A lamp
station should always be located in the shade or protected from direct
sun rays, which would otherwise produce a continuous glare from the
reflector and make the electric light signals invisible. A lamp may
be held in the hand while signaling or fastened to anything that will
aid stability. In permanent and semi-permanent stations an arrangement
for holding the lamp in a fixed position, directed at the receiving
station, should be installed. In addition, a wooden tube tapering
down in size toward the outer end and being 6 ft. to 9 ft. long and
approximately the size of the lamp at the inner end, should be
constructed and also permanently aligned on the receiving station. This
reduces the diffusion of the rays of the lamp, and also minimizes the
possibility of the signals being read where not intended.

=Adjustments of Lamps.=—The reflecting apparatus of a lamp is
carefully adjusted before it is issued. However, it is possible that
a slightly different adjustment will give better results when a new
bulb is inserted. To focus the lamp the light is flashed on some dark
background, such as wall a few yards away, and the screws supporting
the parabolic mirror carefully turned until the light becomes
concentrated in the smallest possible circle. The adjustment screws are
then tightened, but they should never be set tight. If the receiving
operator is having trouble in receiving signals, he will inform the
sending station by sending a series of dots. The sending operator will
then examine his apparatus to see if the lamp is properly directed at
the receiving station, if the reflector is out of focus, or if the
battery has become weak. The receiving operator indicates the manner in
which he is receiving the signals by the method in which he sends the
dots. If the signals become worse, the dots are made more rapidly. As
the adjustment becomes better, the dots are made more slowly. When a
good readable adjustment has been obtained, he will signal BR, meaning
“go ahead.”


PRECAUTIONS IN LAMP SIGNALING.

Don’t leave the lamp cover open when not in use.

Don’t forget to open it when you start to transmit.

Don’t touch the mirror. If necessary, it should be cleaned by wiping
with gauze or cotton or wiped with clean water.

Don’t pull the wire cable fastened to the bottom of the lamp when
removing from the box.

Don’t return broken or burned-out globes to the pouch, but throw
them away unless ordered to turn them in. Don’t use the lamp for
illuminating purposes.

Don’t neglect to keep a constant watch on the stations with which you
are supposed to communicate.


SIGNALING RANGE OF LAMPS.

                  Day.                 Night.
  14 cm    1 to  3 kilometers    2 to  6 kilometers.
  24 cm    1 to  6 kilometers    3 to 10 kilometers.
  35 cm    5 to 10 kilometers    8 to 15 kilometers.

Signals may be transmitted by using either white or red bulbs, but the
range when using red bulbs is reduced approximately 50%.


GENERAL SERVICE CODE AND CONVENTIONAL SIGNALS FOR USE WITH PROJECTORS,
BUZZERS AND WIGWAG.

  A .-     G --.    M --     S ...    Y -.--    5 .....
  B -...   H ....   N -.     T -      Z --..    6 -....
  C -.-.   I ..     O ---    U ..-    1 .---    7 --...
  D -..    J .---   P .--.   V ...-   2 ..---   8 ---..
  E .      K -.-    Q —.-   W .—.   3 ...—   9 ----.
  F ..-.   L .-..   R .-.    X -..-   4 ....-   10 -----


Manner of Sending Messages.

Messages are sent by using the General Service Code and should always
be as short as possible. Every time a letter can be omitted, the chance
of error is reduced. A dot is made by a short flash of about ½ second
duration. A dash is a longer flash of about two seconds duration. The
interval between dot and dash is about ½ second duration. The interval
between letters is about 2 seconds duration. The interval between words
is about 4 seconds duration. In order that lamp signals may be easily
read, it is necessary that the signals be not too rapid, 15 to 20
characters per minute should be taken as the upper limit. Successive
letters must be well spaced. An interval of 2 seconds between letters
will enable the receiving operator to call off each letter to his
assistant as he receives it. In general, two men for each shift are
necessary to operate a lamp station. At the sending station one man
dictates the message letter by letter, and watches the receiving
station for breaks. The other sends the message. At the receiving
stations, one man receives the message and calls it off by letter to
his helper who writes it down. To call a station, its call letter
should be sent several times and at intervals the station calling
should signal its own call letter. As soon as a station observes that
it is being called, it will answer by signaling its call letter and
the signal BR, “go ahead.” The message is then transmitted and the
receiving station acknowledges receipt of each word. By one dot, if
it has been understood. By the interrogation mark, if it has not been
understood and repetition is desired. (While the interrogation is
official, two dots are invariably used for this signal.) At the end of
a message the sending station signals AR, meaning, “end of message.”
The receiving station sends a dot if the message has been understood.


Signaling by Means of Fireworks.

The use of fireworks in modern battles for sending signals has been
greatly developed and is now one of the most important means relied
upon to send a few fundamental signals from the front line of the
infantry to the supporting artillery within the division and between
the ground and the airplanes.


The Fireworks Code.

As the signals that are made by fireworks are always of the most
important character, it is essential that the system for their use be
so perfectly worked out that there will be no chance of confusion. The
smaller the number of signals to be sent by fireworks, the less chance
there is of confusion.


Classification of Fireworks.

The fireworks now being used by the American Army are divided into the
following classes:

1. Very Pistol cartridges.

2. VB cartridges (commonly called “Tromblons”).

3. Rockets.

4. Flares.

The complete directions for firing these various fireworks are
generally attached to the container or box in which they are packed.
They are fully discussed in Annex 14, Translation of the 1917
“Instruction on Liaison for Troops of all Arms, A. E. F.”


1. Very Pistol Cartridges.

The Very pistol cartridges are made in two sizes, a 25-mm size, which
is issued to the companies of infantry, and a 35-mm size, which is used
by the airplanes. These Very pistols fire both signal and illuminating
cartridges.


2. VB Cartridges.

The VB cartridges are fired from a cylinder which is attached to the
end of a rifle. This cylinder, on account of its resemblance to the
old-fashioned blunderbuss (which the French call “Tromblon”) has taken
the name of tromblon and now even the VB cartridges, which are fired
from this cylinder, are often spoken of as Tromblons.


3. Rockets.

The rockets comprise fireworks which are made in the form of cartridges
attached to a wooden stick and fired from a tube or trough. They are
used both for signaling and illuminating.


4. Flares.

Flares are used only in the front lines to mark the position of the
advanced troops when called for by an airplane.


THE USES OF VARIOUS CLASSES OF FIREWORKS.

It will be seen that the above classification of fireworks is an
arbitrary one, made according to the method of projecting them. The
same signal can be made by several different means. The means employed
depend upon the type of fireworks issued to the particular unit using
them and also upon the distance through which the signal must be read.

Flares are not projected at all and consequently have the most limited
range of visibility in any but a perpendicular direction.

The 25-mm Very pistol projects its signals about 200 ft. and can be
seen from the immediate vicinity.

The tromblon projects its signals to a height of 300 ft. and is next in
range of visibility.

The rockets which project a signal at the height of 1000 ft. or over
have the maximum range of visibility.

The 35-mm Very pistol projects signals which are larger than those of
the 25-mm pistol, but throws them a shorter distance (about 150 ft.).
As its use is confined to the airplane this is not a factor in its
visibility.

The following are important uses that may be made of fireworks:

1. By the infantry platoon, company or battalion commander in signaling
to the artillery for a barrage, or otherwise directing the fire of the
artillery.

2. For signaling between the front line troops and the contact airplane
in an advance.

3. Warning of enemy gas attack given by the fireworks signaler nearest
to where the gas is discovered.

4. As a method of acknowledging various visual signals.

5. Occasionally, during the preparation of an attack and upon orders
from the General Staff, fireworks may be used in liaison between the
artillery and the artillery airplanes.


Signaling by Means of Panels.

The increasing use of the airplane in modern warfare has necessitated
the development of reliable communication between it and the earth.
This has gradually been worked out in the following methods:

1. The direct dropping of messages by the airplane.

2. The use of radio apparatus.

3. The use of visual signaling by means of lamps, fireworks and panels.

Panels are pieces of cloth or other materials of various designs which
are spread out on the ground in a manner to be easily seen by the
airplane. They are for three purposes.

1. To signal to an airplane the identity and location of a unit’s
headquarters by the use of its distinctive panel, called its
“identification panel.” This is displayed either when the airplane
requests it (by means of radio) or when the headquarters desires to
attract the attention of the airplane.

2. To signal to the airplane other brief information by the use
of rectangular panels known as “signaling panels” and arranged in
various ways, either by themselves or in conjunction with the unit’s
identification panel.

3. To signal to the airplane the position of the front line in a
daylight advance by the use of special panels called “marking panels.”
These are displayed only when called for by the airplane.

All panels are removed as soon as an acknowledgment is received from
the airplane.

As the use of panels is always in conjunction with airplanes, all panel
signallers should understand some of the uses of the various airplanes.


Miscellaneous Methods of Visual Signaling.

=Wig-Wag Flags.=—Flags for use in wig-wagging are now issued to
divisions under the name of “kits, flag, combination, standard.” Each
kit includes one wig-wag staff and two wig-wag flags, and also two
semaphore staff and two semaphore flags. A division is supplied with
1,022 of these kits. The use of the wig-wag flags is already fairly
well known in the American Army. Signals are transmitted by describing
an arc of 90 degrees to the right and left to form dots and dashes,
and spaces by a downward front motion. The general service can be
transmitted by this means. Wig-wag flag signaling should be thoroughly
understood and practiced by all signal men, as it forms an excellent
method for becoming familiar with the code. Signals can be sent by this
means merely by the use of the hand, and consequently the system forms
an excellent way for troops to put in their time when traveling by
train or on shipboard. Its use in the present war has been limited, but
it will undoubtedly be used more and more, especially when open warfare
is resumed.

=Semaphore.=—Signals by semaphore are transmitted by the arms, either
alone or with the semaphore flags that are issued in the standard
combination flag kits. It is a standard means of communication in the
American Navy and well known in the army. It is not used by the armies
of Europe, but it might serve a useful purpose to linemen and others
for intercommunication.


Radio Equipment.

The Radio receiving sets, type SCR-53 and SCR-54-A form the standard
units for the reception on the ground of signals from airplanes, and
in general, of all damped wave signals or modulated wave signals. The
use for these sets may perhaps be said to be that in connection with
the work of the fire control airplanes in directing the fire of the
artillery. But in addition, they are used for so many other classes of
radio work, that they may indeed be considered among the most important
radio sets.


Type SCR-54 Set.

[Illustration: CIRCUIT DIAGRAM OF SCR-54A RADIO TELEGRAPH RECEIVING SET]

The type SCR-54 set is very similar to the French type A-1 receiving
set. The SCR 54-A set is an improved American product, designed along
the same general lines as the type SCR-54 but differing in some
respects, both mechanical and electrical, to improve the operating
characteristics. The type A-2 and A-2-B antennae are fully described
in Radio Pamphlet No. 2. With their use the receiving sets have
a wave length range of approximately from 150 to 650 meters. If
properly operated, they afford quite sharp tuning. This feature and
their compact, rugged and simple construction have made them of very
considerable value on the Western Front.

As shown in the wiring diagram, Fig. 1, the type SCR-54A receiving set
comprises a primary (antenna) circuit and a secondary circuit, both of
which may be tuned by means of the variable capacitance and variable
inductance comprised in both circuits. The secondary circuit may also
be made aperiodic by placing the switch M on the position marked “AP.”
This connects the condenser in or disconnects it from the circuit. A
separate buzzer circuit is installed in the cover of the box to excite
the set when adjusting the crystal detector.

The adjustable capacitance in each circuit is a variable air condenser
which is adjusted by means of an insulating handle, marked “Primary” or
“Secondary,” mounted directly on the rotating shaft of the condenser.
The relative amount of capacitance in the circuit, corresponding to
the various positions of these handles, is indicated by a pointer
fastened to the shaft, which moves over a dial graduated from 0 to 90.
The position 0 corresponds to the minimum and the position 90 to the
maximum capacitance of the condenser. The two condensers are identical
in design, and have a maximum capacitance of 500 micro-mfd.

The primary and secondary inductances are varied by means of two dial
switches marked “P” and “S,” respectively. The primary inductance
comprises 60 turns of wire divided into six steps of 10 turns each,
while the secondary inductance comprises 60 turns divided into four
steps of 15 turns each. These two inductance coils are wound on
separate wooden cylinders so arranged that their relative positions
may be readily varied. The coupling of the two circuits, which is
accomplished by the mutual induction effect of these two coils, is
varied by changing the relative mechanical positions of the coils. The
secondary coil may be rotated by means of a handle marked “Coupling,”
and a pointer moving over a scale graduated from 0 to 90 indicates its
position. When in the 0 position the axes of the two coils are at right
angles to each other, and the degree of coupling is 0. When in the
position “90” the axes are parallel, and the coupling is a maximum.

The telephone and detector circuit shunts the secondary condenser. This
circuit consists of a crystal detector connected in series with the
telephone receiver which are shunted by so-called stopping condensers.
The latter is a .002 mfd. mica condenser. Two crystal detectors are
furnished with a set; one of them is enclosed in a glass tube, which
protects the crystal from dust or dirt. The other is open, having no
such protecting casing. Either one may be used by screwing it to the
two binding posts of the set marked “Detector.”

The buzzer is mounted in a compartment of set box cover, and consists
of a small buzzer connected in series with a dry battery type BA-4, and
a switch. The buzzer is energized when this switch is closed. A spare
dry for the buzzer, a screwdriver, the enclosed detector, some spare
wire and spare crystals are normally stored in compartments or metal
clips in the cover. Two type P-11 telephone head sets are kept in a
special compartment in the box. This set box when closed may be carried
by a leather strap attached to it.


Method of Operating.

The first step in putting the set in operating condition is to select a
suitable place and set up the antenna. The set box is then installed in
a dry and protected place, and the arial and ground (or counterpoise)
leads are connected to their respective terminals on the operating
panel, and the telephone head set plugged into the jack with the
installation thus completed the first step is to adjust the crystal
detector. To do this, place the “Coupling” handle near the maximum
position, and connect the short piece of wire from the terminal clip
in the buzzer circuit to the “Antenna” or “Ground” terminal of the
operating panel. Close the buzzer switch to energize the buzzer, and
carefully explore the surface of the crystal with the spring contact
point until a sensitive spot is found, as evidenced by a good audible
sound in the telephone receiver. The short wire running from the
buzzer to the panel is then removed and the buzzer stopped by opening
the buzzer switch. Care should be taken not to disturb the crystal
adjustment by mechanical vibration or shock. This adjustment is very
delicate, and if destroyed, it must be restored before any signals
can be received. With the crystal adjusted, the set is then ready for
tuning. The procedure varies somewhat according to whether the wave
length of the station it is desired to receive is known or not.

=(a) Wave Lengths of Signals Unknown.=—The switch M in the center of
the panel is thrown to the position “AP” (aperiodic). This disconnects
the secondary condenser, and makes the secondary circuit responsive
to signals of any wave length. The coupling is made a maximum, and
the secondary inductance dial switch S placed at the position “60.”
The primary inductance switch P is then placed successively at the
positions marked 10, 20, 30, 40, 50 and 60, and, at each point, the
handle of the primary condenser is slowly turned over its full range,
until the loudest signals are obtained in the telephone. The station is
then identified by its call letters, and if it is the station desired,
tuning of the set is completed as explained below. It may happen
however, that in this search for signals, several stations are heard,
simultaneously or for different positions of the handles. The process
of searching is kept up until the desired station, as identified by its
call letters, is heard with the greatest intensity.

The coupling pointer is then moved toward the minimum position, so that
the signals will be just loud enough to be easily read. The switch
M is placed in the position T (tune), which connects the secondary
condenser in the secondary circuit. The secondary circuit is then tuned
by operating the secondary inductance dial switch S and the secondary
in the same way that was followed in tuning the primary. The secondary
circuit is in tune when the signals are heard loudest. The set is then
ready for operation.

If necessary, the strength of the signals may be increased by
increasing the coupling, but this should not be done unless the signal
become too faint to be read, since increasing the coupling increases
the likelihood of interference by other sending stations. When the
coupling is changed, some slight adjustments of the primary and
secondary condensers will be found to improve the signals.

=(b) Wave lengths of Signals Known.=—When the receiving operator has
been advised of the wave length of the signals he is to pick up, the
process of tuning in is somewhat facilitated by the use of the table of
wave lengths which is pasted in the cover of the box.

The primary circuit of the set is first tuned, as explained above, with
the switch on “AP,” the secondary inductance on “60” and with maximum
coupling. After the signals have been identified and the primary has
been tuned to give maximum loudness, the coupling is reduced as before
and the switch M moved to T. The secondary inductance setting to be
used is then given in the table. Thus, for a wave length of 280 meters,
the setting may be 30 or 45. It is best to use the higher value 45.
The final secondary adjustment is then made as before by means of the
secondary condenser.


Use of a Vacuum Tube Detector with the SCR-54 Set.

It is sometimes desirable to use a vacuum tube detector in place of the
crystal detector supplied with the set. In this case, the telephone
stopping condenser of the set must be short circuited by inserting a
dummy brass plug in the telephone jack. The crystal detector is then
disconnected, and wires are connected from the detector binding posts
of the set to the proper terminals of the vacuum tube detector set. The
telephone receivers should not be plugged in, as before, in the jack of
the set box, but must be connected to the proper terminals or jack of
the vacuum tube detector box.


Precautions, Sources of Trouble, Maintenance.

In using this set, care should be taken to always keep it in as dry a
place as possible. It should be kept in a clean condition, especially
the operating panel, the contacts, binding posts, dial switch studs,
and the telephone jacks. Oil or grease on these contacts will make
the connections uncertain and unsteady and impair or even prevent the
satisfactory operation of the set.

The set should be handled carefully to avoid warping the condenser
plates or otherwise damaging the set. No foreign substance should be
placed in the set box. Care should be taken that the telephone receiver
cords do not get wet, for the resulting leakage of current through
them would considerably decrease the strength of signals and introduce
an annoying noise. The telephones do not require any adjustment, and
the earpieces should always be kept screwed up tight. The telephone
receiver should never be taken apart, since their adjustment at the
factory is very accurate and permanent. If it becomes necessary to
remove the cord connections from either the telephones or the plug,
the wires must be connected as found, according to their different
colors. This is important since otherwise the permanent magnets will be
partially demagnetized and the efficiency of the telephone receivers
will be seriously impaired. In packing the set for transportation
the telephone head set receivers are placed face to face so that
the diaphragms will be protected and kept free of mud and dirt. The
telephone cord is then wound around the head band in such a way as to
hold the receivers together. The telephone plug is finally slipped
inside the coil thus formed by the connection cord, and the entire
set is carefully placed in its compartment in the set box. Among the
troubles most frequently encountered are those considered below. It
may happen that the buzzer does not work. This may be due to a poor
adjustment of the buzzer vibrator, or to a run down dry battery. If
the radio does not work it may be because the crystal detector is not
making contact with the sensitive spot. Readjust it with the aid of
the buzzer. No sound in the receiver may be due to the fact that the
telephone is not all the way in the jack, or that it is dirty. In this
case see that the plug is clear in, or remove it and wipe it off with a
clean cloth. Also, the dummy brass plug may be in the telephone jack.
This would prevent operation entirely with the crystal detector.

Scratching noises in the telephone may be the result of wet connection
cord, or the connection at the plug or either telephone receiver may be
loose.

If the antenna or ground connections is loose, or if the ariel or
lead in wire is grounded through a branch of a tree, or in some other
way, the set will fail to operate. Make sure of good insulation all
around. It sometimes happens that a wire will break inside the set box.
This generally occurs to one of the wires connecting the secondary
induction coils to the various taps to the secondary dial switch. One
way to discover this fault is to turn the “Coupling” handle back and
forth; the signals may then suddenly stop for a certain position of
the handle, although they will be audible with the handle on either
side of this position. Finally, a plate of one of the variable air
condensers may become warped and short circuit the condenser. This
is generally evidenced by the fact that the condenser, when varied
over its whole range, does not change the loudness of the signals. In
active service, the receiving sets are required to be in continuous
working condition. To insure this, spare parts must be kept on hand at
all times in order to replace defective parts with the least possible
delay. Such spare parts should include spare crystals, telephones and
telephone cords. Complete extra set should always be in stock at the
central Radio supply station to provide for replacement promptly when
sets are destroyed. The sets in use should also be frequently tested
to determine and readiness for an intensive and continuous activity.
The condenser and inductance circuits should be tested to make sure
that each part of each circuit is in perfect working condition. Testing
of circuit parts may be simply done with a head phone and dry cell, a
click through closed circuits, and the absence of a click through the
condenser circuits, being the indication which should be noted.




CHAPTER XVI.

SMALL ARMS.


Notes on the Automatic Pistol, Cal. 45, Model 1911.

The pistol is known as the Automatic Pistol, Cal. 45, Model 1911. By
caliber is meant the caliber of the bore. All pistols used in the
service are marked on the left side of the receiver, “United States
Property,” and on the right side with the serial number, which must be
memorized by the person to whom the pistol is issued.

It is important that every man have a thorough knowledge of the
nomenclature, care and repair, method of assembling and dismounting the
pistol as well as its use and operation.

=The principal parts= of the pistol are the _receiver, the barrel and
the slide_.

=To Dismount and Assemble the Pistol=:—Press the magazine catch and
remove the magazine. Press the plug inward, turn the barrel bushing
to the right and by easing off on the spring let the plug and spring
protrude gradually. Draw the slide to the rear until the small recess
is opposite the thumb piece of the slide stop. Press gently against
the end of the pin of the slide stop on the opposite side and remove
the slide stop. This releases the link and allows the barrel and the
slide with all its parts to be slid forward off the guide rails of the
receiver.

=To Disassemble the Slide=:—Remove the plug by turning it to the left
and withdraw the recoil spring with its guide from the rear; or remove
the recoil spring guide and withdraw the coil spring with its plug
from the front. Turn the barrel bushing to the left and withdraw it
forward from the slide. The barrel may now be withdrawn from the slide.
To remove the firing pin, press the rear end of the pin forward until
it clears the firing pin stop. Then withdraw the stop downward from
its seat, whereupon the firing pin, the firing pin spring, and the
extractor are removed by withdrawing them to the rear.

For ordinary cleaning, no further dismounting will be found necessary
and no disassembling of the receiver should be permitted except by
permission of an officer. When the interior of the pistol has been
exposed to water, or when it is desired to make repairs, the receiver
may be completely dismounted as follows:

Cock the hammer, move the safety lock to a position half way between
its upper and lower position. Press the end of the safety lock pin on
the opposite side and withdraw the safety lock. Now lower the hammer by
pressing the trigger. Push out the hammer pin and take out the hammer
and strut. Next push out the housing pin. This may require a little
extra pressure. It is the only pin pushed out by pressure from the left
side of the receiver. The main-spring housing may then be withdrawn
downward and the grip safety withdrawn to the rear. This exposes the
sear spring, which is easily removed. By pushing out the sear pin, the
sear and the disconnector are released.

The main-spring housing is disassembled by compressing the main spring,
pushing out the small main-spring cap pin, whereupon the main-spring
cap, the main spring and the housing pin retainer will come out. The
main spring may be easily compressed by using the pin of the slide stop.

[Illustration: THE AUTOMATIC PISTOL, CALIBER 45, MODEL 1911.]

[Illustration: RECEIVER, BARREL AND SLIDE.]

To remove the magazine catch, press the button inward. By means of
a small screw driver or the short leaf of the sear spring, give the
screw head of the magazine catch lock a quarter turn to the left and
remove the magazine catch. The trigger can then be withdrawn to the
rear.

The hammer strut, a small nail or the long arm of the screw driver may
be used to push out all pins except the main spring cap pin and the
ejector pin. To remove these a tack or pin may be found necessary.

To assemble the pistol proceed in the reverse order, except that the
main spring housing should be left to project about one-eighth inch. Do
not push the main-spring housing home and insert the housing pin until
after the safety lock is replaced and the hammer lowered.

=The Operation of the Pistol.=—The act of drawing back the slide in
loading cocks the hammer, compresses the recoil spring, permitting the
magazine follower to raise the upper cartridge into the path of the
slide. Upon releasing the slide, the recoil spring forces the slide
forward, carrying the first cartridge into the chamber of the barrel.
As the slide approaches its forward position, it encounters the rear
end of the barrel, forcing the latter forward. Since the front of the
barrel pivots in the barrel bushing and the rear end is free to swing
upward on the link, the rear end of the barrel is raised, causing
the locking ribs on the outside of the barrel and the inside of the
slide to engage, thus positively locking the barrel and the slide
together. The joint forward movement of the barrel and the slide (about
three-eights of an inch) is stopped when the barrel lug encounters the
pin of the slide stop.

The pistol is then ready for firing. When the hammer is cocked, the
hammer strut moves downward, compressing the main spring. The sear,
under the action of the long leaf of the sear spring, engages its nose
in the notch of the hammer. Upon pulling the trigger and pressing on
the grip safety, the sear is moved, thus releasing the hammer. The
latter then strikes the firing pin which transmits the blow to the
primer of the cartridge. The explosion of the cartridge generates
the necessary gas pressure to force the bullet through the barrel,
the initial muzzle velocity being about 800 ft. per second. The
pressure exerted to the rear against the face of the slide carries
the latter and the barrel to the rear together. But due to the link
attachment, the barrel is almost immediately swung down and unlocked
from the slide, leaving the slide to continue its movement to the
rear, thus opening the breech, cocking the hammer, extracting and
ejecting the empty cartridge and compressing the recoil spring. When
the slide reaches its rearmost position the magazine follower raises
another cartridge into the path of the slide. This cartridge is then
forced into the barrel by the forward movement of the slide as before
described.

Although it might be supposed that the downward swinging of the barrel
would affect the accuracy of the fire, this is not the case. The bullet
has gained its maximum velocity and passed out of the muzzle before the
unlocking movement between the barrel and slide commences.

When the magazine has been emptied the magazine follower is free to
press against the projection on the slide stop, thus forcing the slide
stop into the front recess of the slide, thereby locking the slide
in the open position and reminding the person firing that the empty
magazine must be replaced before firing can be continued.


Interesting Facts about the Pistol.

(a) Weight 2½ pounds. Trigger pull, about 7 pounds.

(b) Rifling, 6 grooves with left-hand twist. The drift due to the
rifling is therefore to the left, but this is more than neutralized by
the pull of the trigger when the pistol is fired from the right hand.

(c) For ranges up to 75 yards the trajectory is very flat and the drift
slight, giving the pistol great accuracy.

[Illustration: COMPONENT PARTS.]

[Illustration: COMPONENT PARTS.

  1.  Receiver.
  2.  Barrel.
  3.  Slide.
  4.  Plunger Tube.
  5.  Slide Stop Plunger.
  6.  Plunger Spring.
  7.  Safety-lock Plunger.
  8.  Slide Stop.
  9.  Rear Sight.
  10.  Front Sight.
  11.  Link.
  12.  Link Pin.
  13.  Barrel Bushing.
  14.  Recoil Spring.
  15.  Recoil Spring Guide.
  16.  Plug.
  17.  Extractor.
  18.  Ejector.
  19.  Ejector Pin.
  20.  Firing Pin.
  21.  Firing Pin Spring.
  22.  Firing Pin Stop.
  23.  Hammer.
  24.  Hammer Pin.
  25.  Hammer Strut.
  26.  Hammer Strut Pin.
  27.  Mainspring.
  28.  Mainspring Cap.
  29.  Mainspring Cap Pin.
  30.  Sear.
  31.  Sear Spring.
  32.  Sear Pin.
  33.  Disconnector.
  34.  Trigger.
  35.  Grip Safety.
  36.  Safety Lock.
  37.  Mainspring Housing.
  38.  Housing Pin.
  39.  Housing Pin Retainer.
  40.  Lanyard Loop.
  41.  Lanyard Loop Pin.
  42.  Magazine Tube.     }
  43.  Magazine Base.     }
  44.  Magazine Pins (2). }
  45.  Magazine Loop.     }  Magazine
  46.  Magazine Spring.   }
  47.  Magazine Follower. }
  48.  Magazine Catch.
  49.  Magazine Catch Spring.
  50.  Magazine Catch Lock.
  51.  Stocks, Right and Left.
  52.  Stock Screws (4).
  53.  Screws Bushings (4).
]

(d) Beyond 250 yards the trajectory is very curved and the drift
becomes considerable. Firing is therefore very inaccurate.

(e) To hit a target at ranges over 75 yards it will be necessary to
lay on a displaced point above and to the right of target for ranges
approximately as follows:

                    _Vertical_            _Lateral_
  _Range, Yards._  _Displacement._  _Displacement, right._
        100            ½ yard          ½ yard
        150          1½ yards         ¼ yard
        200          3     yards       1     yard
        250          5     yards       2     yards

(f) The striking energy of the bullet is sufficiently great to surely
disable a man by causing a dangerous wound at all ranges up to 500
yards.

(g) The pistol has been fired by experts at 25 yards, aimed fire, at
the rate of 21 shots (3 magazines) in 30 seconds. Such rapidity is,
however, not necessary or desirable in service firing. Accuracy is
always the first consideration.


Precautions.

1. Whenever the pistol is taken out of or returned to the arm rack,
also both before and after drill or other exercises with the pistol,
remove the magazine and see that it is empty. Then draw back the slide
which will eject any cartridge in the chamber. Finally look through the
bore to see that the pistol is unloaded and the bore not obstructed by
a plug or wad. Replace all parts, come to raise pistol and lower hammer.

2. Never place the trigger finger within the trigger guard until it is
intended to fire and the pistol pointed toward the target.

3. Do not carry the pistol in the holster with the hammer cocked and
the safety lock on, except in an emergency.

4. Always press the trigger with the forefinger.

5. After each shot relieve the pressure on the trigger so that the sear
may re-engage.

6. When inserting the magazine be sure that it engages the magazine
catch. Never insert the magazine by striking it smartly; always apply a
continuous push.

7. The pistol must be kept clean, free from rust and properly oiled.

8. Never disassemble the receiver except by permission of a officer.

9. In disassembling the receiver be sure that (a) the disconnector and
sear are properly assembled; (b) that the hammer is not snapped when
the pistol is partially assembled; (c) that the stocks are not removed;
(d) that no hammer is used in either assembling or disassembling.


Care and Cleaning of the Automatic Pistol.

In =cleaning= the barrel of the automatic pistol after firing proceed
as follows: Swab out the bore with soda solution to remove powder
fouling. Remove and dry with a couple of patches. Examine to see
that no patches of metal fouling are in evidence, then swab out with
the swabbing solution—a dilute metal-fouling solution. The amount of
swabbing required with the swabbing solution can be determined only
by experience assisted by the color of the flannel patches. Normally
a couple of minutes’ work is sufficient. Dry thoroughly and oil with
sperm oil.

The proper method of =oiling= a barrel is as follows: Wipe the cleaning
rod dry; select a clean patch and thoroughly saturate it with sperm or
light slushing oil, being sure that the oil has penetrated the patch;
scrub the bore with the patch, finally drawing the patch smoothly from
the muzzle to the breech, allowing the cleaning rod to turn with the
rifling. The bore will be found now to be smooth and bright so that
any subsequent rust or sweating can be easily detected by inspection.

The principles as outlined above apply equally well for the care of the
barrel of the sub-calibre cartridge.


MACHINE GUNS AND AUTOMATIC RIFLES AS EMPLOYED BY THE ARTILLERY.

The field artillery employs machine guns and automatic rifles only
defensively, either against hostile aircraft, or against enemy infantry
in case of a break-through. For this reason the tactical use of these
weapons by the artillery is considerably different from that by the
infantry, and the dispositions that must be made are adapted to
particular needs.

       *       *       *       *       *

The field artillery must defend itself:

  (a)  On the march.
  (b)  In position.
  (c)  At the echelon (horse-lines).


Defense on the March.


1. Machine Gun.

Machine guns may be used on the march in case of surprise attack
or against low-flying aeroplanes. Fire on roads and convoys from
low-flying aeroplanes has been developed to such an extent that it is
imperative at all times for a column to be prepared to defend itself
against such attacks.

1. When a battery is in the advanced zone, one machine gun is mounted
on a special mount on the second caisson of the fifth section. This
gun is kept ready for fire at all times, the loaded belt if it is a
Browning, being kept in the loaded position. About 500 rounds Cal. 30
ammunition are carried on the caisson. The machine gunner in charge of
the gun marches with the 5th section.

A mechanic can very easily modify the special mount for the Browning,
for use against aircraft, so that it also will be adaptable for use on
the caisson.

One gun is attached to the fifth section, so that on subdivision of
the battery for action, the other gun will be with the Combat Train or
echelon, being carried in the battery wagon or the park wagon.

The second gun may be carried stored in the battery wagon or on escort
wagon. In position warfare the firing battery goes into position
usually at night. The escort wagon then goes up with tools, officers’
rolls, etc. and the machine gun with its special mount, the regular
tripod, and about 2000 rounds of ammunition. If not carried as stated,
provision must be made for carrying the gun with the firing battery.


2. Automatic Rifles.

The automatic rifles are assigned one to each section.

All eight automatic rifles should be in readiness for instant use
when on the march. They should be evenly distributed throughout the
battery, and handled by men who have had special training. At least two
magazines per gun (40 rounds) should be instantly available. While it
is difficult to bring down a plane with a machine gun or rifle, a well
directed fire will limit the action of hostile planes.

It should be borne in mind that often when in the advanced zone
friendly aeroplanes are detailed to guard a battery on the march. Great
care must be taken to make no mistakes in identifying aeroplanes.
Never shoot at a ship unless the distinctive markings on the wings are
clearly distinguished and identified. Upon subdivision for action,
the automatic rifles go with the section to which assigned. This, of
course, may be varied according to the situation.


(B.) Defense of the Position.

The machine gun emplacement should be carefully selected and
constructed. The first consideration is a good field of fire; the
second is good concealment.

Usually it is placed on a flank of the battery. Situated on the flank
of the battery, a greater field of fire is obtained for the gun.
Moreover when firing against hostile airplanes, the position of the
battery will not necessarily be disclosed. In case the battery is
shelled, the position of the machine gun on the flank renders it less
liable to be hit.

The emplacement for a machine gun at a battery position differs from
those generally built by the infantry in that it is designed primarily
for anti-aircraft shooting.

There can be no overhead cover, all protection being provided by well
constructed concealment. Camouflage must be arranged for and so placed
that it can be instantly thrown aside for firing.

The plans for close defense of the battery should include the
assignment of positions and sectors of fire for the automatic rifles.

The methods of fire and the technical points involved, in firing
against hostile airplanes, will be considered elsewhere. A sentinel
equipped with a pair of field glasses must be on duty in the
emplacement at all times. The members of the machine gun squad are
detailed for this duty by roster.


Types of Anti-Aircraft Mounts.

The Ordnance Department furnishes no anti-aircraft mount, but
improvised mounts can be easily made.


BROWNING MACHINE GUN—MODEL 1917.

The Browning Machine Gun, Model 1917, is water-cooled and is chambered
for caliber .30 U. S. Standard Rifle Ammunition. The gun is classed as
a heavy water-cooled gun, recoil operative and belt fed.

The water jacket holds about 7 pints of water and is perfectly smooth
on its interior. The steam escape tube is in the top of the water
jacket, and is made up of two tubes. They slide one upon the other, the
outer one being a little shorter than the inner one. This allows the
outer tube to slide toward either end and uncover the highest steam
escape hole. The force of recoil is utilized to perform the various
mechanical operations of feeding in the cartridges, loading, cocking,
firing the gun and ejecting the empty shells through the bottom.

The several cams of the gun make each moving part of the gun have a
positive motion.

The feed belt is made of woven fabric and has no metal parts to cause
feed jams and to add extra weight to the piece. Also the metallic
disintegrating links are used with the aeroplane gun. The fibre belt
usually contains from 250 to 500 rounds. The metallic belts can be made
to contain any number of rounds desired.

The gun has very few screws and springs. It is composed of about forty
parts which may be taken down in the field. There are a few parts which
can be assembled incorrectly and it cannot be determined that they are
so assembled until the gun is ready to be put into action. At this
point the gunner will find that the gun will not operate, therefore
great care should and must be used in the study of a quick and positive
assembling.

The weight of this gun is about 30 pounds without water. This weight
makes it necessary to use the gun on a tripod or other suitable mount.


General Data.

  Weight of the gun—no water                   30 lbs.
  Weight of the gun filled                   36.75 lbs.
  Weight of the belt, 250 rounds                15.25 lbs.
  Length of the barrel                          24 in.
  Weight of the belt, empty                     7.5 oz.
  Sight graduated to                            2800 meters.
  Rate of fire (shots per minute)               400-525.
  Aimed shots per minute                        120.
  Calibre of  bore                              .30 in.
  Weight of  bullet                             150  grs.
  Weight of  cartridge                          394  grs.
  Chamber pressure lbs. per sq. in.             47,000-50,000.
  Muzzle velocity (ft. per sec., theoretical)   2700.


THE BROWNING AUTOMATIC RIFLE.


General Description.

The Browning Automatic Rifle, Model of 1918, is chambered for the
United States standard ammunition. This rifle is classified as a light
automatic rifle commonly referred to as the “Light Browning.” It has
been fired 148 shots per minute, semi-automatic, while marching, and
110 shots per minute, semi-automatic, from the shoulder while in prone
position. The rates of fire, which give the best results are from 80 to
100 rounds per minute, semi-automatic marching fire and 50 to 60 shots
per minute, semi-automatic aimed fire.


Operation.

Expanding powder gases furnish the energy for the operation of the
gun. After the gun is fired and the bullet has passed the gas port in
the barrel, the live powder gases expand through the gas port into the
gas cylinder and impinge against the head of the piston. This sudden
blow forces the piston to the rear, compressing the recoil spring
and storing up energy for the return movement. The various lugs and
cams actuate the feeding, firing, extraction and ejection, and also
control the operation of the gun. The feeding is accomplished through
a magazine holding 20 or 40 rounds in double rows. It is held between
the sides of the receiver, in front of the trigger guard. This magazine
is composed of a rectangular tube and a round wire spring wound to fit
the tube. Also there is a bottom plate which slide in the bottom and
forms the rest for the spring. On top of the spring is a follower,
which forces the cartridge up against the lips of the magazine tube and
which holds it in place until stripped out by the lug on the bottom of
the bolt. The automatic action of this gun is not disturbed by holding
it in any position whatever. The magazine can be inserted while the
mechanism of the gun is in either the cocked or forward position.

All parts of the gun are designed so as to impose a minimum of shock
and strain upon them. They are also made strong enough to hold up under
the maximum amount of work that they can be made to perform. There
are few parts that can be assembled incorrectly but the gun will not
function unless these parts are assembled correctly. The dismounting
and assembling of the rifle can be accomplished without the aid of
a single tool unless the barrel and gas cylinder are removed which
necessitates the use of a special spanner wrench provided in the kit.


General Data.

  Weight of gun                               15 lbs. 8 oz.
  Weight of Magazine, empty (20  rounds)      7 oz.
  Weight of Magazine, filled (20  rounds)     1 lb. 7 oz.
  Length of barrel                            24 inches.
  Sights graduated up to                      1,600 yards.
  Calibre bore                                0.30 inch.
  Gas port form muzzle                        6 inches.
  Rate of fire                                500 shots p’m.
  Aimed shots per minute, semi-automatic      60 shots p’m.
  Weight of bullet                            150 grains.
  Weight of Powder                            47 grains.
  Weight of Cartridge (total)                 395.5 grains.
  Chamber pressure, pounds per square
      inch                                    47,000 to 50,000.
  Muzzle velocity                             2,682 ft. p’s.
  Habitual type of fire                       semi-automatic.


Cooling System.

It has no special cooling system or device, the barrel merely being
exposed to the air and the hand of the firer being protected on the
under side of the barrel by a large wooden forearm. Since the barrel
soon becomes very hot, care must be taken to avoid touching it during
firing or for five or ten minutes thereafter.




CHAPTER XVII.

MOTORS.


RECONNAISSANCE CAR.

The reconnaissance car as supplied to regiments of 155-mm howitzers,
motorized, consists of two units: Reconnaissance body, model 1918;
1-ton truck chassis, White, T E B-0.

Further information concerning these units will be found in Ordnance
Handbooks “Reconnaissance Body, Model 1918;” “1-Ton Truck Chassis
White, T E B-0” (No. 1972).


Weights and Dimensions.

  Rated load capacity (body allowance plus
      normal load)                            1 ton—1,040 kg.
  Body weight allowance                       1,500 lb.—862 kg.
  Chassis only                                3,850 lb.—1,750 kg.
  Oil, water and gasoline                     190 lb.—86.5 kg.
  Chains                                      69 lb.—31.5 kg.
  Tool kit                                    37 lb.—16.8 kg.
  Chassis weight on front tires (without
      load)                                   54%.
  Chassis weight on rear tires (without
      load)                                   46%.
  Gross weight (capacity load)                7,150 lb.—3,250 kg.
  Load weight on front tires                  0.78%.
  Load weight on rear tires                   99.22%.
  Gross weight on front tires                 27%.
  Gross weight on rear tires                  73%.
  Overall length of chassis (without body)    205 in.—5,220-mm.
  Overall width of chassis (at widest part)   61 in.—1,550-mm.
  Chassis wheel base                         140 in.—3,560-mm.
  Permissible loading space back of driver’s
      seat                                   97 in.—2,470-mm.
  Width of frame (outside dimension, widest
      part)                                  34 in.—865-mm.
  Height of rear end of frame from ground
      (empty)                                33.75 in.—856-mm.
  Diameter of turning circle (right)         60 ft.—18.3 meters
                             (left)          45 ft.—13.7 meters.
  Tread of wheels                            56 in.—1,422-mm.
  Road clearance under front axle (lowest
      point)                                 10.75 in.—273-mm.
  Road clearance under rear axle (lowest
      point)                                 10 in.—254-mm.
  Length of reconnaissance body, overall     160 in.—4,072-mm.
  Width of body                              59.875 in.—1,522-mm.
  Height of body, overall (including top)    62.125 in.—1,580-mm.
  Weight of body (without equipment)         1,180 lbs.—536 kg.


Brief Description.

The reconnaissance car is provided with a special steel body, mounted
on a 1-ton truck chassis, White Model T E B-0. Four seats are built
into the body. The two front seats are placed back to back. The two
rear seats have a space between them of about 2 feet and are also
placed back to back. There is a compartment between the two pairs of
seats. The floor boards at the back end are extended to form a foot
rest for the rear seat. The car is protected by a canopy top and roll
curtains. A full set of tools is carried on the car. Also five chests
are provided in which are carried all the special equipment assigned
to the car. One chest slides into the body compartment under the rear
front seat, one into the compartment between the rear seats, and the
other three under the rear seat.

The chassis used is similar to that used with the Staff Observation car
on page 95. A complete description and directions for care, operation,
and maintenance are contained in the “Handbook of the Reconnaissance
Car, Model of 1918.” Ordnance pamphlet No. 1972.


ARTILLERY TRACTOR, 5-TON MODEL OF 1917.


Weights and Dimensions.

  Overall length (armored)                133.5 in.—3,400-mm.
  Overall width                           63 in.—1,605-mm.
  Height (armored, to top of muffler)     72.5 in.—1,845-mm.
  Length of ground contact                91 in.—2,315-mm.
  Ground clearance                        11 in.—280-mm.
  Weight (complete with full equipment)   9,200 lbs.—4,180 kg.
  Ground pressure (9 and 11 inch
      treads)                             5.6-4.5 per sq. in.
                                          —0.394-0.316 kg. per sqcm.
  Weight of each  track                   545 lbs.—548 kg.
  Weight of each track shoe (9-in.)       12 lbs.—5.45 kg.
  Width of track shoes                    9-11 in.—299-280-mm.
  Tread of tracks (center to center of
      tracks)                             48.875 in.—1,243-mm.
  Diameter of turning circle (overall
      clearance)                          176 in.—4,425-mm.
  Engine, number  of  cylinders           4
      Bore                                4.75 in.—220.8-mm.
      Stroke                              6 in.—152.5-mm.
      Horsepower at 1,200 revolutions
          per-min                         56.
      Oil reservoir capacity              3.25 U. S. Gal—12.22 liters.
  Road speed-gear used (per hour)
      Low speed at 1,200 rev. per minute
          of engine                       1.94 miles—3.12 kilos.
      Direct speed at 1,200 rev. per
          minute of engine                3.92 miles—6.31 kilos.
      High speed at 1,200 rev. per
          minute of engine                7.37 miles—11.85 kilos.
      Reverse speed at 1,200 rev. per
          minute of engine                1.41 miles—2.27 kilos.
  Capacity of main gasoline tanks
      (two) combined                      24 U. S. Gal.—90.5 liters.
  Capacity of auxiliary tank under
      armor                               10 U. S. Gal.—37.85 liters.
  Capacity of transmission case           3 U. S. Gal.—11.3 liters.
  Capacity of track oiler tank            2.5 U. S. Gal.—9.43 liters.


Brief Description.

The 5-ton artillery tractor, Model 1917, is a self-propelled road
vehicle of the “Track laying” type; that is, the power is transmitted
to the ground through a flexible endless chain which acts as a track
and is composed of steel links and shoes cast integral and connected by
hardened steelpins. The advantage of this type of tractor as compared
with the usual type of wheel tractor or truck, is its ability, due
to very low unit ground pressure, to negotiate very soft and uneven
surfaces, impassable to the usual type of self-propelled vehicle except
under the most extreme difficulties.

The general design and construction of the 5-ton tractor does not
differ materially from that of the modern truck except in the method of
transmitting the power from the transmission unit to the ground. It
is used solely as a power vehicle for hauling howitzers carriages and
caissons. Each carriage and carriage limber are drawn by one tractor
and each pair of caissons are drawn by one tractor.

A complete description and instructions for care, maintenance, and
operation are contained in the “Handbook of 5-Ton Artillery Tractor,
Model of 1917.” (No. 1996).


Outline Specifications.

=Engine.=—Four cylinder, four cycle, valve-in-the-head type. Bore
4.74”. Stroke, 6”. Cylinder case in pairs. Horsepower 56 at 1,200
revolutions per minute.

=Radiator.=—Honey-comb tubular type. Eight separate headers.

=Ignition.=—Eisemann, Model G-4, high tension magneto with automatic
impulse starter.

=Carburetor.=—Model A Schebler carburetor with Stewart vacuum feed
system; 1.5”.

=Governor.=—Centrifugal flyball type mounted on special shaft and
driven off camshaft gear.

=Master Clutch.=—Dry plate multiple disk type.

=Transmission.=—Selective sliding gear type. Three speeds forward, one
reverse. Direct drive on second. Stepped up on high.

=Drive.=—From transmission through bevel gears to steering clutch shaft
through steering clutches to spur pinions, which mesh with intermediate
spur gears, thence through outside gears, encased, to sprocket drive
sleeve and drive sprockets.

=Steering Clutches.=—Two used of dry plate multiple disk type.

=Steering.=—By means of steering clutches operated from hand steering
device and brake bands operated by foot pedals, which act on outside of
steering clutch drums.

=Control.=—Steering gear located on the right hand side. Change gear,
master clutch operating lever, and brake lever, left of steering gear,
left to right respectively. Spark and throttle levers operate on sector
clamped to steering column. Steering clutch pedals right and left at
bottom of, and in front of steering column.

=Brakes.=—One set. External contracting type. Raybestos, or equal,
lined. Operate on steering clutch housings.

=Gasoline Tank.=—Terneplate tanks. Two independent duplicate tanks each
of 12 gallon capacity. Auxiliary terneplate tank under armor, 10-gallon
capacity.

=Main Frame.=—Cast in one piece-open hearth steel.

=Roller Frames.=—Four frames steel channel, joined by oscillating
shaft. Two frames right and left front. Two frames right and left rear.

=Truck Rollers.=—Six on each side of tractor, fitted with roller
bearings, turned on steel gudgeons, flanked to follow track rail.

=Track.=—Made up of malleable iron track shoes with track links.
Integral, fitted with space blocks, and 1.25” pins.

=Track Drive Sprockets.=—Two. Teeth mesh with opening in tracks.

=Blank Sprockets.=—Two. Fitted with roller bearings which turn on steel
gudgeons. Used to adjust track tension.

=Track Supporting Rollers.=—Four on each side of tractor, two mounted
on brackets attached to front roller frame channel, and two in the rear
mounted on spring bracket which is bolted to main frame.

=Springs.=—Four double coil springs at rear, two on each side between
rear roller frame and bracket on main frame and four—two on each side
of equalizing bar at front.

=Equalizing Bar.=—Spring supported on front roller frame sections.


AMMUNITION TRUCK.

The ammunition truck supplied to regiments of 155-mm howitzers, model
of 1918, motorized, consists of two units: Ammunition truck body, model
of 1918; 2-ton truck chassis, Nash model 4017-A and 4017-L.

Further information concerning those units will be found in the
Ordnance Handbooks. “Ammunition truck body, model of 1918” (No. 2002);
“2-ton truck chassis, Nash model 4017-A and 4017-L.”


Weights and Dimensions.

  Weight of body                1,200 pounds.
  Overall length of body        120 inches.
  Overall width of body         56 inches.
  Overall height of body        54 inches.
  Width of floor (inside)       43 inches.
  Length of floor (inside)      114 inches.
  Height of sides (inside)      36 inches.


Brief Description of Ammunition Truck Body.

The ammunition truck body, model of 1918, consists of a box-type steel
body opening only at its rear end. The body is designed to accommodate
original packing cases of any type of ammunition. When this vehicle is
used near the front lines all four sides and its floor are lined with
detachable heavy cocoa matting to prevent undue noise. A tarpaulin
cover attaches to the body, and so protects its contents.

[Illustration: AMMUNITION TRUCK.]

In addition to the designation of “ammunition truck,” as explained
the ammunition body with various loads is designated when mounted
on chassis models as follows: “Wireless,” “Telephone,” “Tanks,”
“Personnel,” “Baggage,” and “Ration.”

The chassis and bodies for the above are identical for all purposes.
The differences in chassis and body equipment and the load carried when
the truck is used for different purposes are noted under tables of
equipment on page 161. All of the above bodies are mounted on a 2-ton
Nash truck chassis.


Outline Specifications of all 2-Ton Chassis, Nash Models

  Rated load capacity                          4,000 lb.—1,820 kg.
  Body weight allowance                        1,200 lb.—546 kg.
  Weight of chassis only                       6,700 lb.—3,030 kg.
  Maximum gross weight (including
      chassis, body and load)                  11,900 lb.—5,420 kg.
  Percentage of chassis weight on front tires
      (without load)                           66.66%
  Percentage of chassis weight on rear tires
     (without load)                            33.33%
  Percentage of load weight on front tires     30.00%
  Percentage of load weight on rear tires      70.00%
  Percentage of gross weight on front tires    45.00%
  Percentage of gross weight on rear tires     55.00%
  Overall length of chassis (without
      body)                                    202.50 inches—5,100-mm.
  Overall width of chassis (at widest
      part)                                    78.50 inches—1,950-mm.
  Chassis wheelbase                            124.00 inches—3,155-mm.
  Length of frame back of drivers seat         117.13 inches—2,980-mm.
  Width of frame (outside dimensions)          38.13 inches—968-mm.
  Height of rear end of frame from
      ground loaded                            35.50 inches—890-mm.
  Height of rear end of frame from
      ground unloaded                          38.50 inches—980-mm.
  Diameter of turning circle                   50.00 feet—15.25 meters.
  Tread of front wheels                        60.50 inches—1,540-mm.
  Tread of rear wheels                         60.50 inches—1,540-mm.
  Road clearance under front axle
      (lowest point)                           14.75 inches—374-mm.
  Road clearance under rear axle
      (lowest point)                           14.75 inches—374-mm.


Brief Description, Models 4017-A, 4017-L, and 4017-F.

The chassis of all these models is of 124-inch wheel base and is fitted
with a Buda model H-U four-cylinder engine, dry disk clutch, four
speed transmission, and a drive to all four wheels through shafts and
internal gearing. Although the greater number of units in all three
chassis are alike, there are certain structural differences which
exist, mainly in the model 4017-F chassis as against the other two. The
4017-F is a two wheel steer chassis, while the others have four wheel
steering. All of them use four wheel drive and braking. The models
4017-A and 4017-L are fundamentally the same, differing only in certain
details of equipment. Model 4017-L has an acetylene generator and
searchlight, and oil side and tail lamps, both speedometer and odometer
and an impulse starter on the magneto shaft, while the 4017-A has no
impulse starter, uses a Bijur electric generator, storage battery and
electric lamps, and is fitted with an odometer only. Aside from the
two wheel steering and the necessary changes brought about by it,
models 4017-F and 4017-L are practically the same, though a few slight
differences exist in the dash, the brake cross shaft and rods and the
wheel universals as described in detail in the Ordnance Handbook No.
1999.

The engine is a standard design L-head, Buda model H-U using force-feed
lubrication, pump cooling, and fitted with a Stromberg carburetor
feeding through cored passages in the cylinder block, and Eisemann
magneto, and on the model 4017-A only, with a Bijur generator.

The clutch is of the dry plate type and the drive from it is through an
open two-joint propeller shaft to a four speed sliding jaw-clutch type
transmission. From the latter extend two-joint propeller shafts, one
forward and one rearward, to internal gear-drive axles. The live member
has exposed axle shafts extending from it, and the ends of these shafts
are fitted with a universal joint and a spur pinion, the latter meshing
with an internal gear bolted to a disk steel wheel. All the wheels
are interchangeable and are all driving and steering wheels in models
4017-A and 4017-L, while in the model 4017-F only the front wheels
steer.

A complete description of the 2-ton truck chassis, models 4017-A,
4017-L, and 4017-F, with instructions for care, maintenance, and
operation, is given in the “Handbook of the 2-ton Chassis Nash Models
4017-A, 4017-L and 4017-F,” Ordnance Pamphlet No. 1999.


HOW TO DRIVE.

Before starting an engine the driver should see that the gear shift
lever is in neutral position and that the emergency brakes are set. The
spark lever should be set at the proper position. If battery ignition
is used it is best to have the lever in full retard position, as the
spark will occur no matter how slow the engine is cranked. If magneto
ignition is used the lever should be advanced slightly as a hotter
spark is obtained in the advanced position than in the retarded. There
is less probability of a kick back when starting on magneto since
it is necessary to turn the engine at a fairly high rate of speed,
approximately 100 R. P. M. to generate sufficient current to produce a
spark.

The position of the throttle hand control should be set so that the
throttle will be slightly open. In case the carburetor is equipped with
an air-choking device this should be closed to cause a rich mixture for
starting.

The ignition switch should be turned on and the engine cranked by
pulling up quickly on the crank handle a quarter turn at a time. If an
electric cranking motor is provided depress the starting button and
advance the spark. If magneto ignition is used it is best to spin the
engine. Crank the engine with the left hand if possible and stand in
such a position that if the engine should kick back the crank will not
cause injury.

After the engine has started release the choke on the carburetor
advance the spark and close the throttle to a position which will
prevent racing. If a special dash adjustment is provided for regulating
the mixture allow this to remain in a position to cause a rich mixture
until the engine warms up.


To Start the Car.

Allow the engine to warm up sufficiently to overcome missing and to run
smoothly. When satisfied that the engine is running properly release
the emergency brake. In case the car is on a grade apply the foot
brake to prevent the car from moving. Press the clutch pedal all the
way down and move the gear shift lever to first speed position. The
clutch should be allowed to engage gradually and at the same time the
throttle should be opened sufficiently to prevent stalling, but not
cause racing of the engine. If the foot brake has been employed it
should be released as the clutch is engaged. After the clutch has been
fully engaged the throttle should be opened sufficiently to accelerate
the car to change to the next higher speed. The throttle should be
controlled by the foot accelerator pedal. Once the car is in motion the
driver must at all times keep his eyes on the road in the direction in
which the car is moving or about to move when changing direction.


To Shift Gears (Increasing Speed).

Before starting a driver should practice moving the gear shift lever
to the different positions and getting his feet and hands accustomed
to the location of the foot pedals and hand levers. Then it will not
be necessary to look away from the road in order to shift gears or in
any other way to control the operation of the car. To change gears the
clutch pedal should be depressed (it may not be necessary to push it
all the way down against the floor boards) and the foot removed from
the accelerator pedal at the same time. Move the gear shift lever from
first to neutral position, pausing if necessary and then move to second
speed position. Engage the clutch immediately and open the throttle
with either hand or foot control as soon as the clutch is engaged.
The process of changing from second to third or third to fourth is
identical. Bear in mind that before each change is made the speed of
the car should be accelerated. Care should be taken when changing from
lower to a higher speed that the car is moving at a sufficient rate of
speed so that an undue strain will not be put on the engine. Practice
alone in driving the particular apparatus will acquaint the driver with
the necessary speed required to change from one gear ratio to another.


To Shift Gears (Decreasing Speed).

When it is desired to change from a higher to a lower gear ratio
release the clutch and allow the hand or foot throttle control to
remain open far enough so that the engine will speed up. Move the gear
shift lever to the neutral position and again engage the clutch for an
instant. Release the clutch immediately and quickly move the gear shift
lever from neutral to the next lower speed position and engage the
clutch immediately, opening the throttle by hand or foot control.

Another method of shifting to a lower gear ratio is to leave the
throttle open and release the clutch just enough to allow it to slip
and the engine to speed up. The gear shift lever should then be moved
through neutral directly to the next lower speed position and the
clutch engaged. This method does not require as much practice but is
objectionable since it wears or burns the clutch facing.


To Stop the Car.

To stop the car, the throttle should be closed, the clutch released,
and the brakes applied, all being performed at the same time. The
amount of pressure applied at the brake pedal depends upon the distance
in which the driver desires to stop the car. Before allowing the clutch
to engage after the car has stopped, move the gear shift lever to the
neutral position. If the car is to stand apply the emergency brakes.
If the engine is to be stopped speed it up by opening the throttle
just before turning the ignition switch to the position “off.” If the
weather is cold use the choke when stopping the engine or set dash
adjustment to give a rich mixture. This will make starting easier if
the engine is started in a reasonable length of time.


Driving Suggestions.

In operating a car it is always best to alternate the service and
emergency brakes rather than to use one continuously, to equalize the
wear on them. When approaching a very steep down grade it is safest
to move the gear shift lever to a lower speed position, closing the
throttle and permitting the car to drive the engine. When the grade
is not excessively steep the engine can be used as a brake with the
position of the gear shift lever remaining unchanged. This will save
the brakes and tend to cool the engine. The brakes should never be
applied suddenly enough to slide the driving wheels except in cases of
emergency. When a stop is to be made apply the brakes soon enough so
that the motion of the car will be gradually diminished and brought to
a stop at the point desired.

To avoid accidents on the road all rules and regulations governing the
driving of motor vehicles on the road should be observed. When turning
corners or approaching cross-roads warning should be given to avoid
collision with other vehicles which may be hidden from the view of the
driver. Before backing the machine the driver should be sure that the
road is clear. In manipulating the car the front wheels should never be
turned by moving the steering wheel when the car is not in motion. This
puts undue strain on the steering apparatus and will cause lost motion
in the steering gear. If it becomes necessary to move the front wheels
of a car while it is standing still, they should be moved by applying
force not only to the steering wheel but also by pulling the front
wheels around.

When a car skids, the tendency is for an inexperienced driver to apply
the brakes and turn the front wheels in the opposite direction to that
in which he is skidding. This should not be done as it only accentuates
the skidding and the car may be ditched or skid into another vehicle or
the curbing. When the machine starts to skid turn the steering wheel
in the direction in which the car is skidding and partially close the
throttle but not entirely, or it will have the same effect as applying
the brakes. When the car straightens out the power may again be applied
gradually, and the machine brought back to the center of the road.
When skidding on narrow roads it is best to apply the power and steer
to the center of the road. This will aggravate the skid for a moment
but brings the machine around at an angle with the front wheels in the
center of the road. The momentum of the car will cause the rear wheels
to climb back onto the road again.


ENGINE TROUBLES.

If the machine will not start the trouble, can only be located by a
systematic search. It is always best to look over the ignition system
first, then see if there is any gasoline in the carburetor. It will
often take some time to find the trouble. However, if the engine once
starts there is little difficulty in locating the trouble as there will
always be an indication which should point to the source of trouble.
The great difficulty with inexperienced drivers is that they do not
reason out the matter carefully before attempting to remedy it. Also an
inexperienced man usually looks for trouble in the same place no matter
what the indication may be. Nearly all difficulties arise from one of
three sources, ignition, carburetion, or engine. These are outlined in
the following table. The trouble is located by the trouble it gives the
driver.


=I. Engine misses=:

 A. Ignition.

  1. Plugs.

   a. Short circuit. b. Broken porcelain. c. Too large a gap.

  2. Cable.

   a. Broken. b. Grounded.

  3. Instrument.

   a. Dirty carburetor. b. Interrupter points on magneto.

 B. Carburetor.

  1. Water in carburetor. 2. Dirt in the line. 3. No pressure or no
  gas.

  4. Too lean a mixture.

 C. Engine.

  1. Cold.

  2. Valves sticking.


=II. Back Fires Through Carburetor:=

 A. Ignition

  1. Wired wrong.

  2. Timed wrong.

 B. Carburetor.

  1. Water in carburetor.

  2. Dirt in line.

  3. No pressure or no gas.

  4. Too lean a mixture.

 C. Engine.

  1. Valve sticking (Inlet).


=III. Engine Knocks:=

 A. Ignition.

  1. Retarded spark. Spark too far advanced.

 B. Engine.

  1. Carbonized cylinders (pre-ignition).

  2. Overheated engine.

  3. Loose bearings.

  4. Loose pistons.


=IV. Engine Lacks Power:=

 A. Ignition.

  1. Retarded spark.

 B. Carburetor.

  1. Too rich a mixture.

 C. Engine.

  1. Exhaust valve not seating.

  2. Carbon in cylinder.

  3. Overheated engine.

  4. Lack of lubrication.

  5. Governor connections sticking.

 D. Brakes.

  1. Dragging.

 E. Clutch.

  1. Slipping.


=V. Engine Overheats.=

 A. Ignition.

  1. Retarded spark.

 B. Carburetor.

  1. Rich mixture.

 C. Engine.

  1. Cooling system.

   a. Fan belt off.

   b. No water.

   c. No circulation.

   d. Anti-freezing mixture.

  2. Carbonized cylinder.

  3. Lack of lubrication.


=VI. Engine Stops:=

 A. Engine and car stop gradually.

  1. Trouble with fuel.

 B. Engine and car stop suddenly.

  1. Mechanical trouble.

 C. Engine stops suddenly, car gradually.

  1. Trouble with ignition.


=VII. Engine Won’t Stop:=

 A. Ignition.

  1. Cable.

  2. Switch.

 B. Pre-ignition.

  1. Carbon in cylinders.

  2. Overheated engine.

Consider how each of these indications may differ so that it is
possible to locate the exact source of trouble without first
investigating. If the car has been on the road for some time and the
engine misses it will either miss regularly in one or more cylinders
or irregularly in all cylinders. If the former, the miss is due to
ignition. The cylinder in which the miss is occurring can be easily
determined by short circuiting each plug with a screw driver. This is
done by allowing the screw driver to touch the central electrode of the
plug and also the engine. When a plug is short circuited and it does
not affect the operation of the engine, it shows there was no spark
jumping across the electrodes of the plug. If the cable to this plug is
disconnected and held a short distance from the electrode of the plug
from which it was removed, a spark will or will not jump this gap. If
it does jump the gap it shows that the plug is short circuited. Then
the plug is either carbonized or the insulator is broken. If a spark
does not occur place the cable near the engine and if a spark occurs it
shows that the gap was too large at the electrodes of the plug. If no
spark occurs it shows that the trouble is not in the plug but at some
point ahead of this. If the engine is firing on all but one cylinder
the trouble must be some place between the distributor rotor and the
plug. First see if the distributor is dirty and then check up the cable
to see if it is broken or grounded. One point to be remembered is that
the parts of the magneto or the battery ignition system incorporated
in the instruments will affect the operation on all the cylinders and
there is no need of looking for the trouble there if only one cylinder
misses. If every other cylinder to fire misses and magneto ignition is
used, it is often due to the time lever housing being jammed over to
one side so that the interrupter points are opened only by one cam. In
no case is it necessary to file the interrupter points to overcome a
miss, for the interrupter affects the operation on every cylinder and
not on one.

If the miss is irregular it is due to carburetor or to fuel trouble. To
locate the trouble open the pet cock at the bottom of the carburetor
and if there is any water in the carburetor it will run out. This
operation also shows whether or not the gas runs freely. If it does not
there may be dirt in the line or no gasoline supply. After everything
else has been tried to overcome the trouble, adjust the carburetor to
compensate for too lean a mixture.

When an engine is first started it will often miss. This is due to the
engine being cold. Under no circumstances should time be wasted to
overcome missing until the engine is warm. If an exhaust valve sticks
it will cause the engine to miss as the gases will be forced out on the
compression stroke. This is difficult to locate as it is a regular miss
but usually results from an overheated engine.

If an engine backfires when first started and does so continuously it
is best to check up on the wiring and timing of the ignition system. If
the engine is running smoothly and suddenly starts to backfire through
the carburetor it is possible that the magneto coupling has slipped.

If there is water in the carburetor it may suddenly shut off the supply
of gasoline and cause so lean a mixture that backfiring results. Dirt
in the line or running out of gasoline would have the same effect. If
backfiring in the carburetor is experienced in addition to the missing
of the engine it is probably due to too lean a mixture. Backfiring also
results from the inlet valve sticking or not seating properly.

If the engine suddenly develops a knock while in operation it may be
due to the ignition being too far advanced for the condition for which
the car is operating and the spark lever should be retarded. This will
be noticed mostly when the car is under a hard pull such as on hard
hills or going through sandy roads. If the engine develops a knock,
after having been run for a short while, which can not be overcome
by retarding the spark it may be due to carbon in the cylinders or
an overheated engine, both of which would cause pre-ignition of the
charge. By pre-ignition is meant that the incoming charge when under
compression is ignited due to the heat in the cylinder regardless of
when the ignition spark takes place. Loose bearings and loose pistons
will knock but these should be easily distinguished from ignition
knocks as they are present at all times.

If the engine shows a lack of power it may be that the ignition system
is too far retarded due to the coupling driving of the magneto having
slipped. If too rich a mixture is used it will cause a loss of power
but can easily be distinguished by the black smoke which is given off
at the exhaust pipe. Every precaution should be taken to locate the
trouble when an engine shows a lack of power as it may be caused from
the valve not seating properly, carbon in the cylinders, overheated
engine, lack of lubrication, or the governor connection sticking.
If lack of lubrication is causing the trouble it will soon lead to
mechanical trouble such as scoring the cylinder walls or burning out
the bearings. An engine will often give an apparent indication of a
lack of power due to the brakes dragging or the clutch slipping.

If an engine overheats it is best to check up and see whether or not
the car is being operated on a retarded spark or if the mixture is
too rich. The usual trouble of the engine overheating are troubles
experienced with the cooling system. Fan belts often break or slip,
the water may have leaked out somewhere in the cooling system, or the
circulation may be stopped up in some way. If anti-freezing mixtures
are allowed to remain in the cooling system in warm weather they will
cause overheating of the engine due to their low conductivity of
heat. Carbon in the cylinder causes the cylinder to overheat and is
detrimental to its operation. If the engine is not lubricated properly
it will overheat due to the additional friction of the parts.

If after the car is in operation the car and engine slow down gradually
the trouble is without doubt due to lack of fuel or some trouble with
the fuel system or the carburetor. When the car stops under these
conditions the engine usually backfires into the carburetor just before
the car stops.

If the car and the engine stop suddenly it is an indication of some
mechanical trouble such as a frozen bearing, broken connecting rod, or
some other part which suddenly puts a brake on the movement of the car.

If the engine suddenly stops operating and the car continues to coast
the trouble can be traced to the ignition system. A disconnected or a
broken wire usually causes the trouble.

If the engine will not stop when the ignition switch is thrown to the
“off” position it is possible with magneto ignition that the cable
between the switch and the magneto is broken or disconnected. That is,
the switch does not connect the primary of the magneto to the ground.
If the engine is overheated, due to lack of proper cooling or carbon
in the cylinders, the engine will continue to operate due to the
pre-ignition.




APPENDIX “A”

GUNNERS’ EXAMINATIONS.


PREPARATION.

In the preparation for the gunners’ examination men should pay
particular attention to the following points.


Setting the Panoramic Sight.

Before starting to use the panoramic sight, the peep sight should be
turned as far as possible to the right or left. This should be done to
make it easier for the gunner to look through the panoramic sight and
also to prevent him from looking through the peep sight.

Men should get in the habit of working from the top of the sight
down, performing their duties _always in the same order_—this is very
important. In other words in indirect laying he sets the deflection,
applies the deflection difference, levels the cross level bubble and
then lays for direction. In direct laying, he sets the deflection,
sets the range, levels the cross level bubble, and lays the piece for
direction and range. In setting the range on the sight shank the gunner
should place his eye _on a level_ with the index so that the range can
be set exactly. If a range of over 500 yards is given, the fast motion
of the scroll gear should be used. As soon as he has laid his gun he
will call “Ready” and step clear of the piece. After he has called
“Ready” _under no circumstances will he attempt to finish any of his
duties_. If he does he will lose that trial.

All scales should be set rapidly. In order to do this, men must not try
to make any mathematical calculations. The setting of sights should be
absolutely mechanical. The gunner should know exactly in what direction
to turn the knobs, wheels and cranks in order to increase or decrease
the settings and to move the bubbles in any particular direction. A
list of reasons for disqualification are given in the Regulations for
Gunners’ Examination.

It is most important in indirect laying that the gunner be assisted by
TRAINED chiefs of sections and No. 2’s. Men should be picked for this
during the earlier part of the course and trained for that work. A
great deal depends on the ability of these men.


Setting the Peep Sight.

In using the peep sight in direct laying the panoramic sight head
should be turned to either flank so that there will be no chance of
the gunners looking through the panoramic sight. The gunner in looking
through the peep sight should keep his eye about six inches from it.


Setting the Quadrant.

Candidates should get in the habit of performing the required duties
in the following order: (1) Setting the site with his =right= hand.
(2) Setting the range with his left hand as prescribed for No. 1
(Instruction Memorandum No. 11—5th hour, 1st week). (3) Centering the
cross level bubble with his right hand. (4) Leveling the range bubble
with his right hand. The candidate should be sure to look and see where
the bubble is before he starts to turn the elevating crank handle. He
should turn the handle quickly. After leveling the range bubble he
calls “Set” and steps clear of the wheels.


Fuse Setting.

Candidates in setting the bracket fuze setter should stand immediately
in rear of it and should crouch down. The corrector should be set
first and the range next, both scales being set with the =right= hand.
His assistant should stand immediately to the left and should pass the
round to the candidate who is being examined, as No. 5 passes the round
to No. 4 in percussion fire. The candidate after setting the scales
rises up, grasps the projectile and inserts it in the fuze setter. He
then sets the fuze and calls “Ready.” The assistant should hold the
projectile so that the lug on the time ring is at 10 o’clock (vertical
clock face). The candidate when he inserts the round in the fuze setter
should place it so that the lug on the time ring falls just to the left
of the rotating pin notch. This is done so that the two shall engage as
soon as possible.

In setting the fuze with the hand fuze setter, the candidate takes
the position prescribed for No. 3 in the service of the piece, his
assistant takes the position of No. 5 when the hand fuze setter is
used. The candidate must be sure to press down on the hand fuze setter
while setting the fuze.

Candidates must be cautioned to remember all necessary data. They
cannot ask the examining officer for any. It must be impressed on them
also that under no circumstances can they start to set the scales
before the instant prescribed by the Regulations for the Gunners’
Examinations.


Drill of the Gun Squad.

Candidates should be familiar with the following paragraphs of the
D. and S. R. F. A.: Formation of the gun squads (135, 138); to form
the gun squad (170-173); to tell off the gun squad (174); post of the
gun squads (175-177); to post the gun squad (178-179); post of the
cannoneers, carriages limbered (180-182); to mount the cannoneers
(183-185); to dismount the cannoneers (186-187); to change posts
(189-190); to move by hand the carriages limbered (191-192); to
leave the park (204); action front (199); posts of the cannoneers,
carriages unlimbered but not prepared for action (188); limber front
and rear (202); action rear (200); limber rear (203); to move by hand
the carriages unlimbered (937); prepare for action (938); march order
(942); posts of the cannoneers, carriages unlimbered and prepared for
action (941); duties in detail of the gunner (845-869); duties in
detail No. 1 (807-891); duties in detail of No. 2 (892-901); duties in
detail of No. 3 (902-911); duties in detail of No. 4 (913-918); duties
in detail of No. 5 (919-924); methods of laying (985-988); and methods
of fire (995-1008).

The questions will only cover the important points covered in the
paragraphs above.


Materiel.

Candidates should be familiar with the following (Handbook of the
3-inch Materiel): Nomenclature of harness and of the parts and
accessories of the wheeled materiel; use of oils; method of cleaning
and lubricating parts and mechanisms; method of cleaning cylinder
oil and of emptying and filling cylinders; use of tools; the kinds
of projectiles, of fuses, and of powder actually issued for use,
and their general purpose and effect, omitting questions as to
construction, weight, manufacture, and technical description; the care
and preservation of saddle and harness equipment in use. Description
of: breech mechanism to dismount, to assemble, elevating screws, to
dismount; to assemble; hub liner, to remove, to assemble; brakes, piece
and caisson, to adjust; wheel, to remove, to replace.


REGULATIONS FOR THE EXAMINATION OF GUNNERS.

A record of marks will be kept during the examination, and at the
conclusion thereof it will be submitted directly to the commander
ordering the examination. The mark received by each man in each subject
will appear opposite the man’s name and the appropriate totals will be
carried out. The tabular list, upon approval by the commander ordering
the examination, will be published in orders.

Men, to be classified as expert first class gunners, must attain an
average of not less than 85% in each of the subjects which follow: to
be classed as first class gunners, a general average of not less than
85% with an average in each subject of not less than 75%; to be classed
as second class gunners, a general average of not less than 75%, with
an average in each subject of not less than 65%.

Examinations will include the following:

                           Value of Subjects.
         Subject.           Gun Batteries.
  Direct laying                   24
  Indirect laying                 24
  Laying for range                18
  Fuse setting                    18
  Drill of the Gun Squad           8
  Materiel                         8

The following general rules will govern the Examining Officers:

1. The conditions of examination will be made, as nearly as possible,
the same for all of the men.

2. Setting of scales will be considered correct if any part of the
index is coincident with any part of the line of the graduation of the
setting ordered.

3. Settings ordered will always be even divisions of the scale, and not
fraction thereof. When a number greater than five is used, it will be a
multiple of five, except in settings of the angle of site and corrector
scales.

4. The man may select any of the assistants authorized.

5. The man is permitted to traverse the piece to the middle point of
traverse before each trial at direct laying.

6. The sight, quadrant, or fuse setter, etc., will be in the position
in which it would be in service before the command for trial with it is
given; the scales will be set at readings different from those to be
given for the trial.

7. The trials for direct laying will be with different deflections and
ranges; for indirect laying with different deflections and deflection
differences; for laying for range, with different angles of site and
ranges. The trail will be shifted in three trials at direct laying.

8. Changes in setting of scales required of men will not exceed the
following: Deflection scale of peep sight, 15 mils; of panoramic sight,
200 mils; deflection difference scale, 30 mils; corrector scale, 10
mils; angle of site scale, 10 mils; range scales, 800 yards. At direct
laying the deflections announced will be between 6370 and 30. At direct
laying the cross level of the tangent sight will be thrown out of level
by the examiner for the trials requiring shifting of the trail.

In time trials, time will be taken from the word at which the candidate
is instructed by this order to commence his trial to the candidate’s
“Ready,” or to the last word of any announcement required. No credits
will be allowed if the candidate performs any part of the trial after
this interval or if the time taken exceeds the maximum given in the
appropriate table of those shown hereinafter.

Should any trial be vitiated through the fault of an examiner, of an
assistant, of the sight or other instrument used, that trial will be
void and the candidate will be given immediately another trial of the
same nature.


Direct Laying.

12 trials: Six with the peep sight and six with the panoramic sight.

The target will represent a shielded gun and caisson and will be
placed, as nearly as practicable, at a distance of 1,000 yards from the
gun used in the trials.

The candidate being seated on the gunner’s seat, an officer of the
battery commands, for example:

1. Target, that gun.

2. Deflection, 10.

3. 2400.

At the indication of the target, the candidate causes an assistant at
the trail to point the piece in its general direction; =at the last
word of the last command= he sets off the deflection and the range
ordered; corrects for difference of level of the wheels; operates the
elevating and traversing apparatus so as to bring the line of sight
upon the target; calls “Ready,” and steps clear.

No credits will be given in the following cases:

(1) If the sight is incorrectly set for deflection or range.

(2) If, when the bubble of the cross level is accurately centered, the
line of sight is found not to be on any portion of the target.

If the piece is found to be correctly laid within the limits
prescribed, credits will be given as follows

  Time in seconds, exactly,
      or less than           16   18   20   21   22   23
                             ————————————————————————————

  Credits                    2.0  1.9  1.7  1.5  1.4  1.3

Indirect Laying.

12 trials.

Two aiming points will be selected, one toward the front and one toward
the rear. They should be of the type used in actual firing and, for
the purpose of this examination, should be about 2 mils in width, well
defined, of such height as readily to be brought within the field of
view, and about 1500 yards distant. They should be clearly pointed out
to the candidates.

All of the guns of the battery will be placed in the order in battery
and a candidate will be assigned to each.

For all trials the board will assume a situation in the conduct of fire
for adjustment by battery, commencing with the first salvo, that will
require commands involving a shift of the trail for this first trial,
and, for all trials, such deflection and deflection difference settings
and changes of settings of scales, not exceeding the limits prescribed
in paragraph 5 of this order, as may reasonably be expected in service.

When the aiming point is in rear the candidate will be allowed an
assistant who, from a position in front of the axle, signals to a man
at the end of the trail to move it, if necessary, so as to bring the
aiming point within the field of view of the sight. When the aiming
point is in front, an assistant at the end of the trail is allowed.

The candidates being seated on the gunners’ seats, an officer of the
battery commands, for example:

1. Aiming point, the chimney on that white house.

2. Deflection, 440.

3. On No. 2 close 10.

At the last word of command for the deflection each man sets off
the deflection; applies the correction for deflection difference
appropriate for his piece; causes the trail to be shifted until the
sight is directed upon the aiming point; corrects for difference of
level of the wheels; raises or lowers the panoramic sight until the
field of view will include the aiming point; traverses the piece until
the vertical hair is on the aiming point; calls “Ready” and steps clear.

The trial being completed and the men again being seated, the officer
commands for example, in continuance of the assumed situation:

1. Right, 120.

2. On No. 4, close 5.

At the last word of command for the deflection, each man operates the
sight and, if necessary, the trail as before; traverses the piece until
the vertical hair is on the aiming point; calls “Ready” and steps clear.

The third and fourth trial is similarly conducted.

No credits will be given in the following cases:

1. If the sight is incorrectly set for the deflection or deflection
difference.

2. If, when the bubble of the cross level is accurately centered, the
vertical cross hair is found not to be on the aiming point.

3. If, at any time during the trial, the man has operated the elevating
device.

If the piece is found to be correctly laid within the limits
prescribed, credits will be given as follows:

  Time in seconds, exactly,
      or less than           18   20   21   22   23   24
                             ————————————————————————————

  Credits                    2.0  1.9  1.7  1.5  1.4  1.3


Laying for Range.

Six trials, using the range quadrant.

The man being seated on the seat on the right side of the trail, an
officer of the battery commands, for example:

1. Site, 280.

2. 3400.

At the last word of the command, the man sets off the angle of site;
sets the quadrant for range; corrects for difference of level of
wheels; turns the elevating crank so as to center the range bubble;
calls “Ready” and steps clear.

No credits will be given in the following cases:

1. If the quadrant is incorrectly set for angle of site or range.

2. If no part of the bubble of the cross level is between the middle
two lines on the glass tube.

3. If there be found to be an error of more than 50 yards in laying for
any range less than 1,500 yards or more than 25 yards for any equal
range to or exceeding 1,500 yards.

If the piece is found to be correctly laid within the limits
prescribed, credits will be given as follows:

  Time in seconds, exactly,
      or less than          14   16   18   19   20   21
                            ———————————————————————————

  Credits                   3.0  2.3  2.6  2.4  2.2  2


Fuse Setting.

12 Trials: 6 with the bracket fuse setter, 6 with the hand fuse setter.

Drill cartridges with fuses in good order set at safety are placed as
in service. An officer of the battery commands, for example:

1. Corrector, 24.

2. 2700.

At the last word of the command for the corrector, in trials with the
bracket fuse setter, the man sets the fuse setter at the corrector,
and, as the data are received, at the range ordered, receives the
cartridge from an assistant, inserts its head in the instrument, sets
the fuse and calls “Ready.”

At the =last word of the command for the corrector=, in trials with the
hand fuse setter, the candidate sets the fuse setter at the corrector,
and, as the data are received at the range, ordered; with the aid of an
assistant, sets the fuse, and calls “Ready.”

No credits are given in the following cases:

1. If the fuse setter is incorrectly set for corrector or range.

2. If the candidate fails to obtain a correct fuse setting within
one-fifth of a second.

If the fuse setter is found to be correctly set and is properly
operated, credits are given as follows:

  Time in seconds, exactly,
      or less than           8    9   10   11   12   13
                            ————————————————————————————

  Credits                   1.5  1.4  1.3  1.2  1.1  1.0


Drill of the Gun Squad.

The subjects will embrace such parts of the following exercises (D.
and S. R. F. A.) as will thoroughly test the candidate’s familiarity
with the service of the piece: Formation of the gun squad (135, 138);
to form the gun squad (170-173); to tell off the gun squad (174);
post of the gun squads (175-177); to post the gun squad (178-179);
posts of the cannoneers, carriages limbered (180-182); to mount the
cannoneers (183-185); to dismount the cannoneers (186-187); to change
posts (189-190); to move by hand the carriages limbered (191-192); to
leave the park (204); action front (199); posts of the cannoneers,
carriages unlimbered but not prepared for action (188); limber front
and rear (202); action rear (200); limber rear (203); to move by hand
the carriages unlimbered (937); prepare for action (938); march order
(942); posts of the cannoneers, carriages unlimbered and prepared for
action (941); duties in detail of the gunner (845-869); duties in
detail of No. 1 (870-891); duties in detail of No. 2 (892-901); duties
in detail of No. 3 (902-911); duties in detail of No. 4 (913-918);
duties in detail of No. 5 (919-924); methods of laying (985-988); and
methods of fire (995-1008).

The questions will only cover the important parts covered in the
paragraphs above.


Materiel.

The examination of each candidate will be sufficiently extended
to test his familiarity with the use and care of the materiel of
his organization, and will be theoretical. The examination will be
conducted by questions on the following subjects: Nomenclature of
harness and of the parts and accessories of the wheeled materiel; use
of oils; method of cleaning and lubricating parts and mechanisms;
method of cleaning cylinder oil and of emptying and filling cylinders;
use of tools; the kinds of projectiles, of fuses, and of powder
actually issued for use, and their projectiles, of fuses, and of powder
actually issued for use, and their general purpose and effect, omitting
questions as to construction, weight, manufacture, and technical
description; the care and preservation of saddle and harness equipment
in use. Description of: breech mechanism, to mount, to assemble;
elevating screws, to dismount, to assemble; hub liner, to remove, to
assemble; brakes, piece and caisson, to adjust; wheel, to remove, to
replace.

Chevrons will be issued to those candidates who qualify and will be
worn as prescribed in orders.


=DON’TS FOR CANNONEERS.=


=Don’ts for All Cannoneers:=

  —Sacrifice accuracy for speed.
  —Guess at the data.
  —Expose yourself.
  —Let your attention be distracted.
  —Make unnecessary moves.
  —Talk.


=Don’ts for Chief of Section:=

 —Forget that you are responsible for the work of your squad.

 —Fail to assist the gunner in laying on the aiming point.

 —Say “Muzzle Right (left),” merely move your hand in the direction you
 desire the trail shifted.

 —Write down the data.

 —Forget your proper pose, covering No. 3 opposite the float.

 —Forget to extend your arm vertically, fingers joined, after the
 gunner has announced “Ready.”

 —Fail to caution “With the Lanyard” for the first shot.

 —Fail to look at both gunner and executive.

 —Command “Fire;” merely drop your arm.

 —Fail to designate who shall assist No. 2 when he is unable to shift
 the trail.

 —Forget to announce “Volley Complete.”

 —Forget to select the individual Aiming Points for the gunner.

 —Forget to announce “No. (so & so) on Aiming Point,” in reciprocal
 laying.

 —Ever say “Range 3000,” merely “3000.”


=Dont’s for Gunner:=

 —Forget to place the sight bracket cover in the left axle seat.

 —Forget to put the sight shank cover in the trail box.

 —Forget to close the panoramic sight box, and fasten it with your left
 hand.

 —Forget to clamp the panoramic sight in its seat.

 —Forget to close the ports in the shield.

 —Forget to put your weight against the shoulder guard while laying.

 —Touch any adjustment after calling “Ready.”

 —Forget to move your head from the panoramic sight after calling
 “Ready.”

 —Lean against the wheel.

 —Fail to take up lost motion in the proper direction.

 —Fail to watch the executive after calling “Ready.”

 —Signal with your hand for movements of the trail.

 —Fail to identify Aiming Points or Targets.

 —Fail to secure hood on sight bracket.

 —Say “Whoa” to No. 2 while the trail is being shifted. Say “Trail
 Down.”

 —Fail to lower the top shield at once at the command “March Order.”

 —Forget to relay vertical hair on A. P. at completion of sweeping
 volley.

 —Forget to set range 1000, deflection zero in “Fire at Will.”

 —Forget to say “Ready” just loud enough for the chief of section to
 hear.

 —Forget to chalk up the deflection on the main shield in reciprocal
 laying.

 —Forget to set site and level bubble (British).

 —Forget to release the brake in trail shifts (British).

 —Forget to count “1001, 1002” to preserve proper firing interval.


=Dont’s for Number 1:=

 —Touch the firing handle until you announce “Set.”

 —Fire the piece with the right hand.

 —Try to throw the drill cartridge over the float by jerking the breech
 open.

 —Slam the breech.

 —Fail to level bubbles.

 —Fail to set and release brake in trail shifts.

 —Fail to look squarely at the scales of the quadrant.

 —Fail to take up lost motion properly.

 —Forget to close the quadrant box.

 —Fire the piece until the command is given.

 —Lean against the wheel.

 —Forget to keep up with the range in direct laying.

 —Forget to lower the top shield immediately at “March Order.”

 —Talk.


=Dont’s for Number 2:=

 —Throw the breech cover on the ground.

 —Fail to engage the handspike.

 —Slam the apron.

 —Put feet on the float.

 —Wait for the command in shifts of 50 mils or more.

 —Move the trail in a series of shifts.

 —Fail to mark off 11 lines 50 mils apart at once on taking your post.

 —Fail to secure the breech cover.

 —Fail to secure the handspike in “March Order.”

 —Run between carriages.

 —Fail to throw empty cartridge cases out of the way of the cannoneers.

 —Forget the tow and waste.

 —Talk.


=Dont’s for Number 3:=

 —Run between the carriages.

 —Throw the muzzle cover on the ground.

 —Throw the front sight cover on the ground.

 —Slam the apron.

 —Fail to see that fuze is set at safety at “March Order.”

 —Fail to look directly down at the fuze setter while adjusting scales.

 —Take right hand from the corrector worm knob and left from the range
 worm crank, during drill.

 —Forget to set range zero in “Fire at Will.”

 —Cross your legs.

 —Forget to set each announced range regardless of the kind of fire
 being used.

 —Talk.


=Dont’s for Number 4:=

 —Throw the fuze setter cover on the ground.

 —Slam the apron.

 —Forget to set the fuze at “Safety” in “March Order.”

 —Fail to glance into the bore to get the alignment.

 —Touch a round after inserting it in the breech.

 —Fail to completely set each fuze.

 —Forget to take the round from No. 5 from beneath in percussion fire
 and from the top when the hand fuze setter is used.

 —Forget to say, “3200, 2, last round,” only loud enough to reach the
 chief of section.

 —Forget to secure the cover on the fuze setter.

 —Attempt to move the caisson with the door open.

 —Forget to set and release the caisson brake (Model 1902).

 —Turn the round to the left after setting.

 —Talk.


=Dont’s for Number 5:=

 —Slam the apron.

 —Attempt to move the caisson with the door open.

 —Forget to put your left elbow on the outside of your left knee in
 using the hand fuze setter.

 —Forget to set the brake on the 1916 caisson.

 —Throw the waterproof caps under your feet.

 —Talk.


TRAINING GUN CREWS.

This article is not intended to cover all of the work of the gun crew,
it is intended merely to cover certain points sometimes lost sight of.
References are to the 3” gun, but any crew efficient in serving that
excellent weapon will have little trouble in mastering any other.

All refinements taught have but one prime object, that is accuracy of
fire. It is of no value to make atmospheric and velocity corrections
if still greater variations are constantly introduced by poor service
of the piece. The foundation of battery efficiency is well-trained
gun crews. Officers may be able to lay out orienting lines with the
greatest facility, may know the range tables in the dark, but it will
avail little if they cannot train men to apply properly and accurately
the data determined.

The safety of our own infantry and the effectiveness of our fire are
absolutely dependent on the continuous training of gun crews, and the
resultant precision and sureness with which they perform their work.
This can only be obtained by constant drill from the day the recruit
joins until the day of his discharge; not by long drills in which
he grows tired and loses interest, but by short periods broken by
instruction in other subjects; not by many hours one week and none the
next, but by a short period every day of the week. The best gunners
grow rusty in a very few days; constant short drills will give results
and are the secret of success. Every man must get instructions every
day, be he raw recruit or expert gunner.

Cannoneers should be taught that the greatest crime that can be
committed in laying the piece is to make an error—the only crime for
which there is no punishment. An error or mistake in the correct
service of the piece should not be punished, but it should be carefully
explained how the efficiency of the battery depends on each member,
and to insure that crime is not committed again, additional hours of
instruction beyond that required for the rest of the crew will be
necessary.

Every man must be on his toes from the time he comes in sight of his
gun, every movement at the piece must be at a run. Slow and sleepy
motions of one man will kill all the snap and energy of every other
member of the crew. Do not, however, confuse speed of performing any
given motion with hurry in execution of detail. For example, the gunner
must move with snap and energy in getting his eye back to the sight
and his hand on the traversing handwheel after the piece is fired,
but he must never be hurried in getting the vertical wire exactly on
the aiming point, or in making the ordered changes in the deflection
setting. Stop watches should not be used. They are a fruitful cause
of errors. Speed comes from continual practice and it cannot be
artificially attained by stop-watch timing. Do not understand that
speed is not desirable, it is highly desirable, but practice alone will
give it and it will nearly always be found that the best-trained crew
is the fastest crew. Competitions between crews must be for accuracy,
not speed. If every motion is made with a snap and at a run the results
as regards speed will be satisfactory.

The accuracy of fire is affected by brakes not being adjusted for equal
tension, by direction of recoil not being in line with the trail, by
No. 2 sitting on the handspike and shifting his weight after the gunner
has called “Ready;” by No. 1 jerking the firing handle; by the gunner
not keeping his shoulder against the guard; by elevating cranks not
being properly assembled; by sights and quadrants not being properly
adjusted or locked with means provided (this subject deserves several
pages); by variations in the amount of oil in the cylinder; by improper
adjustment of the gland; by the gunner coming on to the aiming point
sometimes from the right, sometimes from the left; by the No. 1
centering the bubble sometimes from front to rear, sometimes from rear
to front.

You may have stood behind a battery firing and noticed how one or
two guns jump violently in recoil, while others would hardly disturb
the proverbial glass of water on top of the wheel, although all guns
of equal service. This was due almost entirely to the lack of proper
adjustment of some of the parts mentioned above.

Every member of the crew must know his duties so well as to make his
motion automatic; the direction to turn the various handwheels, milled
heads, and gears to obtain the desired result, and he must always do
these things in the same way. The effect of small differences in laying
may be graphically shown the gun crew by firing sub-caliber ammunition
at a small arms steel target which rings a bell when a bull’s-eye
is made. Erratic shots means poor adjustments of equipment or poor
training of the gun crew. Pleas that worn material or lost motion, or
defective ammunition are the causes of erratic shooting are largely
excuses for ignorance, laziness, and lack of proper instruction. Worn
materiel requires more makeshifts, takes longer to lay and more careful
watching, so that fire cannot be so rapid, but except for wear in the
bore of the gun it is possible to do almost as accurate shooting with
worn materiel, especially if the new materiel has not been thoroughly
worked in.

Among the more important duties of the men may be mentioned in the
following:

=Chief of Section.=—Must teach his men to have pride in the gun they
serve, and the reputation of the section. He shows each member how the
accuracy of firing is dependent on him, and that one man may ruin the
best efforts of all the others. He must keep his materiel as clean as
when it left the makers hand, every part functioning properly, every
screw and nut tightened, no burred nuts or bolts, or missing split
pins. He helps each member to take a pride in keeping the part for
which he is responsible as clean as a new pin and in perfect condition.
He sees that the various canvas covers and sponge and rammer never
touch the ground where they will gather dirt. He knows the proper use
of his tools, and the correct adjustment of the firing mechanism. He
must be able to assemble and disassemble blindfolded the firing lock
and breech mechanism. In firing he knows the settings of all scales
without reference to a data book.

=The Gunner.=—Knows that turning the levelling screw clockwise moves
cross bubble to the right; that turning scroll gear clockwise increases
the range; that turning the peep sight screw clockwise increases
deflection, and so on with all handwheels, etc., that he operates and
must know these things so well that he operates them in the proper
direction automatically. Must always bring vertical wire on aiming
point from the left to take up any play in traversing mechanism. He
verifies that he is on the aiming point after the breech is closed
and if there is any delay, again immediately before firing. He gets
his eye back to the sight and relays _immediately_ the gun returns to
battery. He knows his scale readings at all times. He keeps his sight
scrupulously clean, never permits his finger to touch the objective
prism when turning the rotating head, nor wipes off eye piece with
hand. He keeps his shoulder against the guard at all times.

=The Number 1.=—He knows his site and range scale readings without
having to look at them. In centering the bubble he brings it always
from front to rear to take up play in the elevating mechanism. He
centers the bubble so accurately that it is not the thickness of a
sheet of tissue paper nearer one graduation than the other, and what is
most important he sees that it stays there until he fires the pieces,
when he promptly recentres it. (The latitude allowed in centring the
bubble by our gunners’ examination is responsible for 20 per cent. of
our field probable error.) He must not fire the piece with a jerk but
with a constant even pressure, else he may destroy all his accuracy of
levelling. The same principle applies if he uses the lanyard. He keeps
his quadrant free from any sign of dirt and assures himself that it is
in perfect condition. If the gunner fails to keep his shoulder against
the guard when the piece is fired he reminds him of it. In centring
the bubble or setting the scales he gets his eye squarely opposite the
scale or bubble.

=The Number 2.=—He knows the width of the spade, float, etc., in mils,
and is able to make any shift under two hundred mils, within 5 mils. He
shifts the trail so as to bring the direction of recoil in line with
it (except for moving targets). In receiving empty cases he should not
permit them to strike the trail or throw them against each other, as
they must then be resized before they can be again used. If he sits on
the handspike he must not shift his weight after the piece is laid.

=The Number 3.=—He knows that turning the corrector worm knob clockwise
decreases the setting; turning the range worm crank clockwise increases
the range. In making these settings he keeps his eye squarely over the
scales. He knows his scale settings at all times. He is taught to keep
his fuze setter and its cover clean, and is shown how a small pile of
dirt or wax behind the stop pin or in the rotating pin notch can throw
out his settings and ruin the reputation of his section. Gum from the
fuze often collects in these places. The surest way is to keep a match
stick handy and clean out these places whenever there is a lull in the
firing.

=The Number 4.=—If necessary to reset the fuze he must turn the
projectile until it brings up against the stop pin, then cease all
turning movement and draw the projectile straight out of the fuze
setter. If he continues the turning motion unconsciously he can easily
alter the setting by a fifth of a second. In loading he is careful not
to strike the fuze against the breech and so alter the fuze setting.

=The Number 5.=—He knows where the rotating pin notch is in the fuze
setter, and where the corresponding pin is on the fuze. He places the
fuze so that the pin is seated in the notch with little or no turning
movement and turns rapidly but with no more force than required. He is
careful to set all fuzes with the same force, that is, not turn one
with a violent twist and the next barely up to the stop.




APPENDIX “B”—Comparative table of guns used in World’s War.


  ——————————————————————————+—————————+—————————+—————————+—————————
                            |         |         |         |   Gt.
                            | Austria,| France, | Germany,| Britain,
                            |   1905  |  1897   |   1906  |  1917
  ——————————————————————————+—————————+—————————+—————————+—————————
  Caliber, inches           |    3.01 |    2.95 |    3.03 |    3.3
  Weight of shrapnel, lbs.  |   14.72 |   16.00 |   15.00 |   18.00
  Muzzle velocity, f. s.    |   1640  |   1750  |   1760  |   1680
  Muzzle energy, ft. tons   |    275  |    335  |    242  |    340
  Weight of gun             |    700  |   1000  |    766  |    880
  Weight of gun and         |   2000  |   2650  |   1860  |   2600
    carriage                |         |         |         |
  Weight of g., c. and      |   3750  |   4150  |   4200  |   4100
    limber                  |         |         |         |
  Maximum elevation         |     18  |     18  |     16  |     33
  Total traverse, degrees   |      8  |      6  |      8  |      8
  Length of recoil, inches  |    51.5 |     47  |     44  |  28-48
  Height of wheels          |    4’3” |     4’  |    4’5½”|   4’3”
  Independent line of sight |    No.  |   Yes.  |    No.  |   Yes.
  Sights, goniometric,      |         |         |         |
    telescopic, panoramic,  |     P.  |     G.  |   T. G. |  O. P.
    ordinary                |         |         |         |
  Breech block, wedge       |         |         |         |
    swinging, eccentric     |     W.  |   E. S. |     W.  |     S.
    screw.                  |         |         |         |
  Traverse, axle or pintle  |     P.  |     A.  |     P.  |     A.
  Recuperation, spring or   |         |         |         |
      hydro-pneumatic       |     S.  |     H.  |     S.  |     H.
  Length of gun, calibers   |     30  |     36  |    27.3 |    28.0
  Width of track, inches    |     60  |     60  |     60  |     66
  Range, maximum            |   6400  |   7550  |   7600  |   9000
  ——————————————————————————+—————————+—————————+—————————+—————————

  ——————————————————————————+—————————+—————————+—————————+—————————
                            |         |         |   U.    |   U.
                            |  Italy, | Russia, | States, | States,
                            |   1912  |  1903   |  1902   |  1916
  ——————————————————————————+—————————+—————————+—————————+—————————
  Caliber, inches           |    2.95 |    3.   |    3.   |    2.95
  Weight of shrapnel, lbs.  |   14.3  |   14.41 |   15.00 |   16.00
  Muzzle velocity, f. s.    |   1510  |   1930  |   1700  |   1600
  Muzzle energy, ft. tons   |    224  |    273  |    300  |    311
  Weight of gun             |    690  |    785  |    710  |    765
  Weight of gun and         |   2260  |   2075  |   2230  |   3000
    carriage                |         |         |         |
  Weight of g., c. and      |   3350  |   3850  |   3730  |   4400
    limber                  |         |         |         |
  Maximum elevation         |     65  |     16$ |     16  |     53
  Total traverse, degrees   |     52  |     5½  |      8  |     45
  Length of recoil, inches  |  18-53  |   42.5  |     50  |  18-46
  Height of wheels          |    4’3½”|   4’4”  |   4’8”  |   4’8”
  Independent line of sight |   Yes.  |    No.  |    No.  |   Yes.
  Sights, goniometric,      |         |         |         |
    telescopic, panoramic,  |  T. P.  |  O. P.  |  O. P.  |  O. P.
    ordinary                |         |         |         |
  Breech block, wedge       |         |         |         |
    swinging, eccentric     |     W.  |  S. B.  |  S. B.  |     W.
    screw.                  |         |         |         |
  Traverse, axle or pintle  |     P.  |     A.  |     A.  |     P.
  Recuperation, spring or   |         |         |         |
      hydro-pneumatic       |     H.  |     S.  |     S.  |     S.
  Length of gun, calibers   |     30  |     30  |    29.2 |    30.8
  Width of track, inches    |     58  |     60  |     60  |     60
  Range, maximum            |   8850  |   7800  |   6500  |   9650
  ——————————————————————————+—————————+—————————+—————————+—————————




APPENDIX “C”


TABLE OF EQUIVALENTS.

  1 mil.                  3.37 minutes.
  1 meter (m)            39.37 inches.
  1 centimeter (cm)        .3937 inch.
  1 millimeter (mm)        .03937 inch.
  1 kilogram (kg)         2.2046  pounds.
  1 dekagram (dkg)         .3527  ounce.
  1 gram                 15.432 grains.
  1 liter                 1.05671 quarts (U.S.).
  1 inch                  2.54 centimeters.
  1 foot                   .3048  meter.
  1 yard                   .9144  meter.
  1 square inch           6.452 square centimeters.
  1 cubic inch           16.39 cubic centimeters.
  1 cubic foot             .02832 cubic meter.
  1 cubic yard             .7645 cubic meter.
  1 ounce                28.35 grams.
  1 pound                  .4536 kilogram.
  1 quart (U. S.)          .9463 liter.
  1 degree               17.777 mils.
  1 kilogram (kg) per    14.223 pounds per
      square centimeter      square inch.




INDEX


  Abatage, French 75-mm, 95

  Action of Recoil Mechanism, 3-inch Gun, 70

  Aiming Circle, 274

  Air and Liquid Pumps, 155-mm Howitzer, 189

  American 75, 105

  Ammunition, 199

  Ammunition 3-inch Gun, 214

  Ammunition, Definition of, 11

  Ammunition Marking, 233

  Ammunition Truck, 334

  Angle of Site Mechanism, American 75, 127

  Anti-Aircraft Guns, 60

  Armament, Modern, 46

  Army Artillery, 57

  Artillery, Definition of, 11

  Artillery Tractor, 330

  Assembling 3-inch Gun, 76, 242

  Assembling American 75, 133

  Automatic Pistol, 315

  Automatic Rifle, 322, 325

  Axles, Discussion, 44


  Ballistics, Definition of, 11

  Battery Commander’s Telescope Model 1915, 270

  Biblical References to Artillery, 16

  Bicarbonate of Soda, 239

  Bore, Definition of, 11

  Borax, 238

  Bracket, Fuze Setter, 283

  Breechblock, 4.7-inch Gun, 156

  Breechblock, British 75, 150

  Breechblock, French 75, 87

  Breechblocks, Discussion of, 31

  Breech, Definition of, 12

  Breech Mechanism 3-inch Gun, 63

  Breech Mechanism, American 75, 106

  Breech Mechanism, G. P. F., 162

  Breech Mechanism, 155-mm Howitzer, 173

  British 75, 147

  Browning Automatic Rifle, 325

  Browning Machine Gun, 323

  Built-up Guns, Discussion of, 29


  Caisson 3-inch Gun, 74

  Caisson, Definition of, 12

  Caliber, Definition of, 12

  Camp Telephone, 286

  Canvas Buckets, 241

  Care of 3-inch Gun, 242

  Care and Cleaning of Cloth, 252

  Care and Cleaning of Leather, 249

  Care and Cleaning of Metal, 252

  Care and Inspection of Sights, 267

  Care and Preservation, French 75, 101

  Care of Guns During Firing, 253

  Care of 155-mm Howitzer, Notes on, 194

  Care and Preservation of Materiel, 236

  Carriages, Gun, 3-inch, 65

  Carriage, Gun, Definition of, 12

  Carriage, American 75, Description, 111

  Carriage 4.7-inch Gun, Description, 154

  Carriage 155-mm Howitzer, Description, 179

  Cartridge Case, Care of, 219

  Cartridge, Case, Definition, 12

  Charge, Definition, 12

  Classification of fuzes, 224

  Cleaning Material, 236

  Cleaning Schedule, 254

  Clock Oil, Use of, 237

  Cloth Equipment, Care of, 252

  Coal Oil, Use of, 237

  Combination Fuzes, Tables of, 232

  Cannoneers’ “Don’ts”, 360

  Conventional Signals, 301

  Corps Artillery, Discussion, 55

  Cradle, Definition of, 12

  Cradle, American 75, Description, 118

  Cradle, G. P. F. Description, 162

  Cradle 155-mm Howitzer, Description, 181

  Cradle 3-inch Gun, Description, 66

  Cylinders 3-inch Gun, Care of, 244

  Cylinders 155-mm Howitzer, Description, 181

  Cylinders, Outer, Discussion, 31


  Detonating Fuzes, Tables of, 229

  Detonators, Discussion, 199

  Dismounting American 75, 133

  Dismounting French 75, 101

  Dismounting 3-inch Gun, 76

  Divisional Artillery, 47

  “Dont’s” for Cannoneers, 363


  Elevating Gear, 3-inch Gun, 66

  Elevating Mechanism, American 75, 129

  Elevating Mechanism, British 75, 150

  Elevating Mechanism, Definition, 13

  Elevating Mechanisms, Discussion, 37

  Elevating Mechanism 4.7-inch Gun, 157

  Elevating Mechanism, 155-mm Howitzer, 185

  Engine Oils, Use of, 238

  Engine Troubles, Motors, 345

  Equalizing Gear, American 75, 127

  Equivalents, Tables of, 371

  Explosives, Discussion, 199

  Extractor, French 75, 87


  Faults, Common in Telephones, 297

  Field Glasses, 283

  Filling American 75 Cylinders, 145

  Filloux 155-mm Gun, 160

  Fire Control Equipment, Definition, 13

  Fire Control Instruments, 260

  Firing Mechanism, American 75, 110

  Firing Mechanism, French 75, 89

  Firing Mechanism, Definition, 13

  Firing Mechanism, 4.7-inch Gun, 156

  Firing Mechanism, 3-inch Gun, 64

  Firing Mechanism, 155-mm Howitzer, 175

  Fireworks, Signalling, 304

  Fixed Ammunition, 203

  Flags, Signalling, 285

  Floats, American 75, 114

  French 75, 84

  Front and Rear Sights, 3-inch Gun, 260

  Fulminates, 199

  Fuzes, 221

  Fuze Classification, 224

  Fuze, Definition, 13

  Fuze Setter, 3-inch Gun, 283

  Fuze Setters, Definition, 13


  General Service Code, 301

  Gribeauval, Reference to, 20

  G. P. F. (Grande Puissance Filloux), 160

  Gun, Definition, 13

  Gun Crews, Training of, 367

  Gun Carriages, Discussion, 33

  Gun Carriage, 3-inch Gun, 65

  Gunners Examinations, 352

  Guns, Care of in Firing, 254

  Guns Used in World War, 370

  Gustavus Adolphus, Reference to, 18


  H and H Soap, Use of, 239

  Hand Fuze Setter, 284

  Heavy Field Gun, Discussion, 58

  Heavy Field Howitzer, Discussion, 59

  High Explosives, 202

  History and Development of Materiel, 16

  Hollingshead Soap, Use of, 239

  How to Drive Motors, 340

  Howitzers, 155-mm, Care of, 194

  Howitzer, 155-mm, Model 1918, 167

  Howitzer, Definition of, 13

  Hydroline Oil, Use of, 239


  Independent Angle of Site, 111

  Initial Velocity, Definition of, 13


  Lamps, Signalling, 298

  Lanterns, 242

  Lavaline, Use of, 238

  Leather, Care of, 249

  Light Gun and Howitzer, Discussion, 48

  Light Slushing Oil, Use of, 237

  Limber, Definition of, 14

  Limber, 3-inch Gun (Caisson), 72

  Line Sights, 258

  Louis XIV, Reference to, 20

  Liquid Pumps for 155-mm Howitzer, 189

  Lubricating Oil, Use of, 236

  Lye Powdered, Use of, 238


  Machine Gun, Browning, 324

  Machine Guns, Use of, 321

  Marks on Ammunition, 233

  Materiel, Definition of, 14

  Medium Gun and Howitzer, 55

  Metal, Care of, 252

  Modern Armament Discussion, 46

  Monocord Switchboard, 288

  Motors, 328

  Mortar, Definition of, 14

  Motorization, 50

  Muzzle, Definition of, 14

  Muzzle Velocity, Definition of, 14


  Naphthaline, use of, 238

  Neats-foot Oil, Use of, 237

  Nitrogen Compounds, 203


  Observing Instruments, 270

  Obturation, 204

  Ogive, Definition of, 14

  Ordnance, Definition of, 14

  Outer Cylinders, Discussion of, 31


  Paint, Rubberine, 238

  Panels, Signalling, 305

  Panoramic Sight, Model 1917, 260

  Panoramic Sight, Model 1915, 263

  Paulins, 242

  Percussion Primers, 208

  Petrolatum, 237

  Picket Ropes, 242

  Piece, Definition of, 14

  Pistol, Automatic, 315

  Polish, Gibson’s Soap, 238

  Powder Bags, 206

  Preparation for Gunners Examinations, 349

  Pressure Gauge, 155-mm Howitzer, 192

  Primers, 206

  Primer, Brown Enamel, 238

  Primer, Definition of, 14

  Primer, Pressing, 208

  Projectile, Definition of, 14

  Projectile, Shape and Nomenclature, 209

  Projectors, Signalling, 298

  Propelling Charges, 201

  Pumps, Air and Liquid, 189


  Quadrant, Gunners, Definition of, 14

  Quadrant, Range 3-inch Gun, 265

  Quadrant, Sight 155-mm Howitzer, 192


  Radio, SCR 54 and 54a, 307

  Railway Artillery, Discussion, 60

  Range Finder, 278

  Range Quadrant 3-inch Gun, 265

  Recoil Mechanism, Definition of, 14

  Recoil Mechanism, Discussion, 39

  Recoil Mechanism, 3-inch Gun, 68

  Recoil Mechanism, American 75, 120

  Recoil Mechanism, British 75, 150

  Recoil Mechanism, French 75, 99

  Recoil Mechanism, 4.7-inch Gun, 156

  Recoil Mechanism, G. P. F., 162

  Recoil Mechanism, 155-mm Howitzer, 182

  Reconnaissance Car, 328

  Regulations for Gunners’ Examinations, 352

  Rifle, Definitions of, 14

  Rifling, Definition of, 15

  Rounds, Definition of, 15

  Runners, 285


  Sal Soda, 239

  Schedule, Cleaning, 254

  Semi-fixed Ammunition, 204

  Semaphore, 306

  Separate Ammunition, 204

  Shell, Definition of, 15

  Shell Fillers, 201

  Shields, Discussion of, 43

  Shrapnel, Definition of, 15

  Sights, 258

  Sights, Care of and Inspection, 267

  Sights, Discussion of, 43

  Sights, Front and Rear, 258

  Sights, Line, 258

  Sights, Panoramic, 260

  Signals, Conventional, 301

  Signal Equipment, 285

  Small Arms, 315

  Soap H and H, 239

  Soap, Castile, 239

  Soap, Saddle, 239

  Spades, American 75-mm, 114

  Spare Parts 3-inch Gun, 240

  Sperm Oil, Use of, 237

  Swabbing Solution, 239

  Switchboard, Monocord, 288


  Table of Equivalents, 371

  Table of Explosives, 202

  Table of Fuzes, 232

  Telephone, Camp, 286

  Telephone Faults, 295

  Telescope, B. C. Models, 1915 and 1917, 270

  Tools and Accessories 3-inch Gun, 239

  Training Gun Crews, 364

  Trail, 3-inch Gun, 66

  Trail, American 75, 114

  Trail, British 75, 150

  Trail, 4.7-inch Gun, 157

  Trail, G. P. F. Gun, 165

  Trails, Definition of, 15

  Trails, Discussion of, 45

  Traversing Mechanism 3-inch Gun, 66

  Traversing Mechanism, American 75, 133

  Traversing Mechanism, British 75, 153

  Traversing Mechanism, 4.7-inch Gun, 156

  Traversing Mechanism, G. P. F., 165

  Traversing Mechanism, 155 Howitzer, 187

  Traversing Mechanism, Definition of, 15

  Traversing Mechanisms, Discussion of, 36

  Tubes, Discussion of, 27

  Twist, Discussion of, 29

  Type SCR 54 and 54a Radio, 307


  Vacuum Tube Detector, 311

  Vaseline, 237

  Variable Recoil, American 75, 126


  Weights and Dimensions 3-inch Gun, 62

  Weights and Dimensions 4.7-inch Gun, 154

  Weights and Dimensions American 75, 105

  Weights and Dimensions British 75, 147

  Wheels, Care of, 248

  Wheels, Discussions of, 44

  Wheels, 3-inch Gun, 65

  Wheels, 4.7-inch Gun, 157

  Wheels, G. P. F., 165

  Wig-Wag, 306

  Wire-Wrapped Guns, Discussion, 28




  Transcriber’s Notes

  pg 8 Changed: Harley-Davidson motorcicles
                to: Harley-Davidson motorcycles

  pg 9 Changed: Gun Carriage, Ear View
                to: Gun Carriage, Rear View

  pg 23 Changed: which could best be handled to manuever
             to: which could best be handled to maneuver

  pg 24 Changed: we fined the now famous long range
             to: we find the now famous long range

  pg 34 Changed: If the guns were rigidily attached
             to: If the guns were rigidly attached

  pg 35 Changed: The leverages with which the overturning
             to: The leverage with which the overturning

  pg 46 Changed: little more than phyrric victories
             to: little more than pyrrhic victories

  pg 57 Changed: and the concensus of opinion
             to: and the consensus of opinion

  pg 63 Changed: Breezh recess.
             to: Breech recess.

  pg 100 Changed: (2) The diaphram with its hollow rod
              to: (2) The diaphragm with its hollow rod

  pg 100 Changed: may communi?ate freely with the air
              to: may communicate freely with the air

  pg 101 Changed: Canoneer Dismountings.
              to: Cannoneer Dismountings.

  pg 110 Changed: forced over horiztonal shoulders
              to: forced over horizontal shoulders

  pg 124 Changed: (b) Flood slides with oil,
              to: (c) Flood slides with oil,

  pg 131 Changed: by means of the elevating haulwheel
              to: by means of the elevating handwheel

  pg 135 Changed: Remove lower splint pin
              to: Remove lower split pin

  pg 194 Changed: which the levling mechanism is operated
              to: which the leveling mechanism is operated

  pg 217 Changed: The shell is always issued filled and fuxed
              to: The shell is always issued filled and fuzed

  pg 232 Changed: Will be abanonded by French
              to: Will be abandoned by French

  pg 236 Changed: materiel may funtion easily
              to: materiel may function easily

  pg 239 Changed: Water, 4 oz. or 1/4 pnt
              to: Water, 4 oz. or 1/4 pint

  pg 245 Changed: results from firing of two two kinds
              to: results from firing of two kinds

  pg 250 Changed: have been in contact with meta
              to: have been in contact with metal

  pg 269 Changed: for the same angle of site (roughtly estimated
              to: for the same angle of site (roughly estimated

  pg 272 Changed: To set up the tesescope.
              to: To set up the telescope.

  pg 272 Changed: and sphercial aberration
              to: and spherical aberration

  pg 276 Changed: is set up and horiontal
              to: is set up and horizontal

  pg 276 Changed: turn the teslecope until
              to: turn the telescope until

  pg 278 Changed: Substracting one reading from the other
              to: Subtracting one reading from the other

  pg 280 Changed: and the verticle spindle
              to: and the vertical spindle

  pg 285 Changed: reliable means of communition
              to: reliable means of communication

  pg 289 Changed: connecting by independant wires
              to: connecting by independent wires

  pg 291 Changed: pivot at one to press against the shutter
              to: pivot at one end to press against the shutter

  pg 292 Changed: tip spring and the anvil are then contact
              to: tip spring and the anvil are then in contact

  pg 292 Changed: equipment also inculdes a night bell
              to: equipment also includes a night bell

  pg 297 Changed: station instrument will be imparied
              to: station instrument will be impaired

  pg 298 Changed: particularily in an advance
              to: particularly in an advance

  pg 303 Changed: The Very pistol cartrdiges
              to: The Very pistol cartridges

  pg 309 Changed: adjust the crustal detector
              to: adjust the crystal detector

  pg 312 Changed: kept in a clean contion
              to: kept in a clean condition

  pg 313 Changed: Scratching noises in the telepone
              to: Scratching noises in the telephone

  pg 314 Changed: evidenced by the fact that the condeser
              to: evidenced by the fact that the condenser

  pg 323 Changed: differs from those generaly built
              to: differs from those generally built

  pg 336 Changed: differing only in certin details
              to: differing only in certain details

  pg 341 Changed: may again be applied graually
              to: may again be applied gradually

  pg 354 Changed: maximum given in the appropropriate
              to: maximum given in the appropriate

  pg 361 Changed: completion of sweeping voley
              to: completion of sweeping volley