CHARACTERISTICS OF INFANTRY WEAPONS

CONTENTS

CHAPTER	DESCRIPTION	PARAGRAPH
I	Grenades, Pistol, Carbine, Smoke	1 - 5
II	The Light machine Gun	6 - 8
III	The 60-mm Mortar	9 - 11
IV	Caliber .30 Machine Gun (Heavy), and 81-mm Mortar	12 - 13
V	Guns and Howitzers and the Caliber .50 Machine Gun	14 - 17

CHAPTER I

GRENADES, PISTOL, SMOKE

1. Introduction. Infantry is the arm of close combat. It is required to advance for considerable distances under fire; to use its weapons in conjunction with the supporting fire of the other arms to beat down the hostile fire; to close with the enemy and drive him from his position; to exploit success; and to hold ground which has been gained. The accomplishment of these missions requires varied types of action. Accordingly, the infantry is armed with a number of different weapons of widely different characteristics. Some of them are designed for fire action, others for shock action, and some for both. Several deliver flat-trajectory, grazing fire and a solid projectile; others a high, curved trajectory and a projectile which bursts on impact.

One characteristic, however, is common to all; they must be able to accompany and support the infantry soldier in all phases of action. This essential common characteristic exercises a great restrictive influence on infantry armament, since it definitely limits the weight of our weapons, and consequently their range and power.

Because of their wide difference in characteristics, the combined employment of infantry weapons requires skillful teamwork. This teamwork is obtained by grouping the weapons and their operators in a basic combat unit, the infantry battalion, under the control and coordination of the battalion commander. Those weapons not organically a part of the battalion, such as the 75-mm howitzer and the 105-mm howitzer, operate in close coordination with, or actually become temporarily a part of, the battalion when it is committed to action.

2. Grenades.

a. General. Grenades arc classified generally as those which are propelled by hand (hand grenades) and those which are propelled by the rifle (rifle grenades).

b. Hand grenades.
(1) Characteristics and tactical use.
The hand grenade (Plate 1) is a curved-trajectory weapon complementary to the rifle and bayonet of the individual soldier. It is used against an enemy sheltered behind cover to cause casualties or force him into the open. The grenade is hand thrown. Its radius of effect is from 15 to 30 yards, depending on the type of grenade. Small particles capable of inflicting serious wounds may travel as far as 100 yards from the point of detonation. Its short range (30 to 45 yards) prevents the use in open warfare of grenades having a wide radius of effect.

The difficulty of supply and distribution, together with the weight of the projectile. limit, the number which can be carried by the soldier and restricts its offensive use. The difficulty of supply largely disappears in the defense. Special types of grenades are used for lachrymal or irritating gases. Grenades are issued as required to individual infantrymen before entry into combat.

(2) Types.
Hand grenades are divided into the following three general types:

1.	Fragmentation grenades, containing an explosive charge in a body designed to fragment with the action of the bursting charge.
2.	Grenades containing a chemical filler.
3.	Grenades designed for training or practice.

(3) Grenade fillers.
The filler is tbe substance contained in the body of a grenade. It may be a powerful explosive, as in the case of the fragmentation grenade, or a gas or smoke-producing substance. Those used are:

EC (explosive company) blank fire smokeless powder. This is a commercial type, granulated nitrocellulose powder, generally pink or yellow in color. It is less powerful than TNT and is exploded by ignition rather 1han detonation. Grenades loaded with this material can be issued fuzed and ready for use and are, in general, not susceptible to mass detonation.


PLATE 1 - Hand Grenade MK II.

Ttinitrotoluene (TNT). TNT is rather stable in character, but unlike blank fire powder it explodes by detonation. Grenades filled with TNT are not stored or issued with the fuze assembled. TNT-filled grenades arc no longer manufactured but may be issued until the stock is exhausted. TNT in block form is used for demolition work, such as destroying certain grenade duds, and can be used in making improvised grenades.

Chloracetophenone (CN). This is a lachrymatory (tear) gas which produces a severe burning sensation in the eyes, causing intense weeping. In one type of irritant hand grcnade, CN is combined with diphcnylamincchlorarsine.

Diphenylaminechloranine (DM). DM is a gas which causes a burning sensation in the nose and throat and a heavy or tight feeling in the chest. There is also a nauseating effect. the degree of which depends on the concentration of the gas and the length of exposure. Grenades filled with chemicals, because of their small capacity, arc no considered suitable for war use, but are very effective in riots, civil disorders, etc.

(4) Grenade components.

(a) Time fuse. Time fuse, or safety fuse, is a cord containing a slow-burning powder train. The time fuse issued to the service is known commercially as Dickford fuse and burns at the approximate rate of 15 inches per minute. Time fuse should always be tested before using to determine its rate of burning. The time fuse in most of the grenade firing mechanisms is cut to burn for 5 seconds.

(b) Detonators. A detonator is a metal capsule filled with a detonating explosive such as fulminate of mercury. Commercial detonators come in 10 sizes, numbered 1 to 10. The higher numbered sizes arc larger and contain increasing amounts of the detonating mixture. No. 6's and No. 8's are the ones used in grenades. Detonators are sensitive to heat, shock, and friction and should be handled carefully at all times.

(c) Fuzes. The fuze is the mechanism that fires the grenade. All grenade fuzes are time and automatic. Time means that the grenade is fired after a certain Lapse of time and not on percussion. Automatic means that the fuze begins to function automatically as it leaves the hand, providing the safety cotter pin has been removed, thus providing a safety factor by eliminating the necessity of starting the action of the mechanism before the grenade is on its way. As to their final action, fuzes may be classified as detonating or igniting.

A detonating fuze contains a detonator (i.e. a small quantity of violent and comparatively sensitive explosive) which sets off the more inert explosive charge, in the case of a fragmentation grenade, or which bursts the case and liberates the filler, in the case of some chemical grenades. Igniting fuzes arc those that contain a small quantity of black powder, or a powder pellet that ignites the filler as though a lighted match were applied.


PLATE 2 - Fragmentation Hand Grenade, MK II (Sectional View).

(5) The fragmentation hand grenade.

this is the grenade generally thought of fragmentation, Mk II" (see Plate 2). When the term "hand grenade" is used. Officially it is designated "Grenade, hand", The body of this grenade is made of cast iron and is about the size of a large lemon. The outside surface is deeply serrated horizontally and vertically to assist in forming uniform fragments when the grenade explodes. The bursting charge is 0.74 ounce of EC blank fire powder, and the grenade is fuzed with the M1O igniting fuze. This grenade should never be thrown unless cover is at hand behind which the operator and friendly troops may secure shelter. Fragments may By over 200 yards. An older type filled with TNT and shipped unfuzed, may still be issued although no longer standard.

The practice grenade, designated officially "Grenade, hand, practice, Mk II", is similar in appearance to the fragmentation grenade, but it is loaded with a light charge of black powder pressed into pellet form and contained in a paper tube. After the fuze is assembled in the grenade, this charge is inserted in the filling hole which is closed with a cork. This grenade is safe for training purposes as it does not fragment. The light black powder charge blows out the cork, giving a light report and a puff of smoke.

(6) The gas grenades. These grenades are of the same general type, the variations being in the filler. They are:

Grenade, hand, gas, irritant, CN-DM, M6 (sec Plate 3).
This grenade has a cylindrical body made of tin plate. The body contains perfora. tions or vents which are covered with squares of adhesive tape. When the grenade functions these patches arc blown or burnt off and the gas escapes. The chemical filler is composed of a mixture of CN-DM and a small amount of blank fire powder. Two seconds after the primer is fired the grenade begins to generate a gas having a pungent odor. One second later the gas reaches full volume and the grenade functions for 25 to 35 seconds.

Grenade, hand, gas, irritant, CN, M7.
This grenade is similar to the M6 grenade but is filled with CN only instead of with the CN-DM mixture,


PLATE 3 - Irritant Gas Grenade.

(7) Throwing technique.

(a) Importance.
Grenade throwing is the most important phase of hand grenade training. The thrower must always follow accurately the prescribed method of arming and throwing so that in the latter stages of training these operations will be performed mechanically. Perfection of throwing form, accuracy, and range are the desired factors in grenade throwing. Accuracy and range are attained by practicing the prescribed throwing form. Due allowance may be made, however, for an individual's conformation.

(b) To hold grenade (Plate 4).
The grenade should be held in the right band with the safety lever firmly pressed by the palm. The forefinger of the left hand is inserted through the safety-pin ring. (A left-handed man may hold the grenade in his left hand.) In this position the safety pin can be removed without altering the grip for throwing. The thrower must take every precaution after the safet:y pin has been withdrawn not to release his grip on the lever until the grenade is thrown. The thumb and forefinger of the right hand should be around the upper-horizontal serration of the fragmentation hand grenade, Mk II. The grenade should not be gripped directly under the fuze head because this will result in inaccuracy, tumbling of the grenade in flight, and reduction of the range. The fuze head has, on occasion, been caught by the fingers of the thrower, causing the grenade to drop immediately upon leaving the band.

(c) General rules for throwing.
The grenade is thrown by a combination of a shot put and baseball catcher's peg motion. The biceps muscle of the throwing arm should be contracted just before throwing. The grenade is released just before the arm is fully extended. It is given a spinning motion by being released over the tips of the fin! efs l\S it leaves the hand so that it will rotate around its longer axis, fuze to the rear, during its flight to the target.

The maximum range is obtained when the grenade leaves the hand, traveling at an upward angle of 45°, The hand being at the shoulder, to execute the throw, carry the right band forward and upward without twisting the wrist. The left arm always counterbalances the movement of the right arm. If the grenades are striking to the right or left of the target the entire body should be shifted to the left or right. For the first practice no attempt should be made to throw over 20 yards as the throwing arm might be injured. Thirty-five yard, is considered a good range after the first 100 grenades have been thrown at an average rate of 30 or 40 grenades a day for 3 or more days. A 5O-yard range is above average.


PLATE 4 - Method of Holding the Grenade.

(d) To throw from standing position (Plate 5).
The thrower facing the target, the commands and manner of execution are as follows:

Stand. Face to the right. Move the left foot 1 ½ to 2 feet toward the target, with the toe pointing in the general direction of the target. Assume a well-balanced and easy position. With the hands down and in front of the center of the body, grasp the grenade in the prescribed manner. When dummy grenades are used the left forelinger grasps the right thumb to stimulate the grasping of the safety-pin ring.


PLATE 5 - To Throw from a Standing Position.

Pull pin. Pull out the safety pin with a twisting-pulling motion, holding the bands as nearly as practicable in front ot the center of the body. When dummy grenades are used simulate this movement.

Prepare to throw. Quickly bring the right arm into position, the elbow at the height of and on line with the shoulders, palm of the hand up, and near or touching the shoulder. At the same time extend the left arm, palm of the hand down, in the direction of the target. The weight of the body is on the right foot. The body is bent to the right, right knee bent, eyes sighting over the left hand to insure direction and then fixed on the target, If throwing from a trench or throwing pit, the eyes should be fixed on the parapet or top of pit.

Throw. Quickly move the right arm upward and to the front without twisting the wrist and release the grenade just before the arm is folly extended, being sure to impart a spinning motion. At the completion of the throw the left foot and right toe are on the ground.

Recover. Resume the position of Stand.


PLATE 6 - To Throw form Kneeling Position.

(c) To throw from kneeling position (Plate 6).
The thrower, facing the target, executes the commands in the following manner:

Kneel. Face to the right, kneel on the right knee, right leg to the rear, left leg and foot pointing in the general direction of the target. The weight of the body is on the right knee.

Pull pin. The execution is the same as for the standing position. Prepare to throw. The execution is the same as for the standing position except that the weight of the body is on the right knee.

Throw. The execution is the- same as for the standing position except that the body is brought to rest by the chest coming in contact with the left knee and upper leg at the completion of the throw.

Recover. Resume the position of Kneel.

(f) To throw from prone position (Plate 7).

The thrower, facing the target,executes the commands in the following manner:

Lie down. Assume a prone position, as shown in Plate 7. The body is on a line approximately in prolongation of the target, so that when the position Prepare to throw is taken it will be unnecessary to shift the feet or left knee. Either check is near or on the ground. Hold grenade as described in paragraph 2b (7) and as shown in Plate 4, but in front of the head, as shown in Plate 7.

Pull pin. Hold the grenade in front of the head and pull the pin in the same manner as described for the standing position.


PLATE 7 - To throw from Prone Position.

Prepare to throw. Draw back the hands and arms so that the hands arc near the shoulders, left hand and forearm flat on the ground, right forearm and wrist only on the ground; shove the body upward, pivoting the weight of body on the left knee; straighten the right leg and extend it straight to the rear. Hold the body upright. Do not push up with the hand holding the grenade. Keep this hand clear of the ground. Continue until a kneeling position is assumed. Being now in a kneeling position, kneeling on the left knee, assume the same positions for the hands, arms, body, and eyes as given for the standing position.

Throw. The execution is the same as for the standing position. Stop the forward motion of the body by placing the right hand on the ground after the throw, permitting the body to continue to the ground. This position will leave the right hand near the head and the left band near the waist on the left side. The left hand can be used to carry another grenade to the right hand for the next throw.

Recover. Place the left hand ne%t to the right in front of the head. Resume the position of Lie down.

(g) To throw from prone position (Advancing) (Plate 8). The body of the thrower can be advanced about 2 feet at each throw if this is desired. The commands and movements are the same as for the prone position except in Prepare to throw. As the hands arc brought back advance the left knee as far as possible. The distance that the left knee is advanced is the distance that the body will be advanced for each throw.


PLATE 8 - To Throw from Prone Position (Advancing).

3. Pistol. a. General. The automatic pistol is not employed in collective action by the infantry. It is an arm of emergency, intended for individual defense at close quarters by personnel not armed with more effective weapons such as the rifle or the automatic rifle. The automatic pistol is a recoil operated, magazine-fed, self-loading hand weapon. The gas generated in a cartridge fired in the pistol, in addition to propelling the bullet, is used to perform the functions of extracting and ejecting the empty cartridge case, cocking the hammer and reloading. The pistol is designed to fire the ball cartridge, caliber .45 Ml911. The magazine holds seven cartridges. The pistol fires once with each squeeze of the trigger and when the last cartridge in the magazine has been fired the slide remains open. By depressing the magazine catch the empty magazine falls out, permitting the insertion of. a filled magazine and making seven more shots immediately available. Rate of fire is limited by the dexterity of the operator in inserting new magazines and his ability to aim and squeeze the trigger.

The pistol is about 8.6 inches long and weighs (with magazine filled) approximately 2.4 lbs. A filled magazine weighs about .5 lb. Maximum range is approximately 1,600 yards (at an angle of elevation of 30 °) but the effective range is actually about 75 yards. Two models of the automatic pistol are issued, M1911 and M1911Al. The latter model embodies some slight but rather effective improvements in general design, but for all practical purposes there is no difference.

b. The mechanism of the automatic pistol (Plate 9) is best learned by disassembling and assembling. This is performed in the following sequence:

(1) Disassembling, (see Plate 9.)

Remove the magazine by pressing the magazine catch. Press the recoil spring plug inward, and turn the barrel bushing to the right until the recoil spring plug and the end of the recoil spring protrude from their seat, releasing the tension of the recoil spring. As the recoil spring plug is allowed to protrude from its scat, the finger or thumb should be kept over it so that it will not jump away and be lost or strike the operator. Draw the slide rearward until the smaller rear recess in its lower left edge stands above the projection on the thumb piece of the slide stop; press gently against the end of the pin of slide stop which protrudes from the right side of the receiver above the trigger guard and remove the slide stop. This releases the barrel link, allowing the barrel with the barrel link and the slide to be drawn forward together from the receiver, carrying with them the barrel bushing, recoil spring, recoil spring plug, and recoil spring guide.

Remove these parts from the slide by withdrawing the recoil spring guide from the rear of the recoil spring and drawing the recoil spring plug and the recoil spring forward from the slide. Turn recoil spring plug to right to remove from recoil spring. Turn the barrel bushing to the left until it may be drawn forward from the slide. This releases the barrel which with the barrel link may be cirawn forward from the slide and by pushing out the barrel link pin the barrel link is released from the barrel.

Press the rear end of the firini pin forward until it clears the firing pin stop which is then drawn downward from its scat in the slide; the firing pin, firing pin spring, and extractor arc then removed from the rear of the slide. The safety lock is readily withdrawn from the receiver by cocking the hammer and pushing from the right on the pin part or pulling outward on the thumb piece of the safety lock when it is midway between its upper and lower positions. The cocked hammer is then lowered and removed after removing the hammer pin from the left side of the receiver. The mainspring housing pin is then pushed out from the right side of the receiver which allows the mainspring housing to be withdrawn downward and the grip safety rearward from the handle. The sear spring may then be removed. By pushing out the sear pin from the right to the left side of the receiver, the sear and the disconnecter are released.


PLATE 9 - Automatic Pistol, Caliber .45 M1911 A1. Sectional View.

To remove the mainspring, mainspring cap, and housing pin retainer from the mainspring housing, compress the mainspring and push out the small mainspring cap pin. To remove the magazine catch from the receiver, its checkered left end must be pressed inward, when the right end of the magazine catch will project so far from the right side of the receiver that it may be rotated one-half turn. This movement will release the magazine-catch lock from its scat in the receiver, when the magazine catch, the magazine catch lock, and the magazine catch spring may be removed.

With the improved design of magazine catch lock (M-l911 Al) the operation of dismounting tl1e magazine catch is simplified. When the magazine catch has been pressed inward the magazine catch lock is turned a quarter turn to the left by means of a screw driver, or the short leaf of the sear spring. The magazine catch with its contents can then be removed. The improved design will be recognized from the fact that the head of the magazine catch lock is slotted.

The trigger can then be removed rearward from the receiver. The hammer strut or the long arm of the screw driver can be used to push out all the pins except the mainspring cap pin, lanyard loop pin, and ejector pin. The slide stop plunger, the safety lock plunger, and the plunger spring may be pushed to the rear out of the plunger tube.

The magazine should not be disassembled except for cleaning or to replace the magazine follower or magazine spring. To disassemble proceed as follows:

Push the magazine follower downward about one-fourth inch; this compresses the magazine spring. Insert the end of a drift through one of the small holes in the side of the magazine to hold the magazine spring, then slide out the magazine follower. Hold hand over end of the magazine before removing drift from hole to prevent magazine spring from jumping away.

(2) Assembling.
Proceed in the reverse order. It should be noted that the disconnecter and sear are assembled as follows: Place the cylindrical part of the disconnecter in its hole in the receiver with the flat face of the lower part of the disconnecter resting against the yoke of the trigger. Then place the sear, lugs downward, so that it straddles the disconnecter. The sear pin is then inserted in place so that it passes through both the disconnecter and the sear. The sear, disconnecter, and hammer being in place and the hammer down, to replace the sear spring, locate its lower end in the cut in the receiver with the end of the long leaf resting on the sear; then insert the mainspring housing until its lower end projects below the frame about one-eighth inch, replace the grip safety, cock the hammer, and replace the safety lock; then lower the cocked hammer, push the mainspring housing home, and insert the mainspring housing pin.

In assembling the safety lock to the receiver use the tip of the magazine follower or the serew driver to press the safety lock plunger home, thus allowing the seating of the safety lock. It should be remembered that when assembling the safety lock the hammer must be cocked.

When replacing the slide and barrel on the receiver care must be taken that the barrel link is tilted forward as far as possible and that the barrel link pin is in place. c. Functioning.
(1) Method of operation. A loaded magazine is placed in the receiver and the slide drawn fully back and released, thus bringing the first cartridge into the chamber. (If the slide is open push down the slide stop to let the slide go forward.) The hammer is thus cocked and the pistol is ready for firing. If it is desired to make the pistol ready for instant use and for firing the maximum number of shots with the least possible delay, draw back the slide, insert a cartridge by hand into the chamber of the barrel, allow the slide to close, then lock the slide and the cocked hammer by pressing the safety lock upward and insert a loaded magazine. The slide and hammer being thus positively locked, the pistol may be carried safely at full cock and it is only necessary to press down the safety lock (which is located within easy reach of the thumb) when raising the pistol to the firing position.

The grip safety is provided with an extending horn which not only serves as a guard to prevent the hand of the shooter from slipping upward and being struck or injured by the hammer, but also aids in accurate shooting by keeping the hand in the same position for each shot and, furthermore, permits the lowering of the cocked hammer with one hand by automatically pressing in the grip safety when the hammer is drawn slightly beyond the cocked position. In order to release the hammer, the grip safety must be pressed in before the trigger is squeezed.

(2) Safety devices.

It is impossible for the firing pin to discharge or even touch the primer except on receiving the full blow of the hammer. The pistol is provided with two automatic safety devices. They are, first, the disconnecter, which positively prevents the release of the hammer unless the slide and barrel are in the forward position and safety interlocked. This device also controls the firing and prevents more than one shot from following each squeeze of the trigger.

Second the grip safety which at all times locks the trigger unless the handle is firmly grasped and the grip safety pressed in. In addition, the pistol is provided with a safety lock by which the closed slide and the cocked hammer can be positively locked in position.

(3) Detailed /functioning.

The charged magazine is inserted in the receiver and the slide drawn once to the rear. This movement cocks the hammer, compresses the recoil spring, and when the slide reaches the rear position the magazine follower raises the upper cartridge into the path of the slide. The slide is then released and being forced forward by the recoil spring carries the first cartridge into the chamber of the barrel. As the slide approaches its forward position, it encounters the rear extension of the barrel and forces the barrel forward; the rear end of the barrel swings upward on the barrel link, turning on the muzzle end as on a fulcrum. When the slide and barrel reach their forward position they are positively locked together by the locking ribs on the barrel and their joint forward movement is arrested by the barrel lug encountering the pin on the slide top. The pistol is then ready for firing.

When the hammer is cocked the hammer strut moves downward, compressing the mainspring, and the sear under: action of the long leaf of the sear spring engages its nose in the notch on the hammer. In order that the pistol may be fired the following conditions must exist:

The grip safety must be pressed in, leaving the trigger free to move, The slide must be in its forward position, properly interlocked with the barrel so that the disconnecter is held in the recess on the under side of the slide under the action of the sear spring, transmitting in this position any motion of the trigger to the sear. The safety lock must be down in the unlocked position so that the sear will be unlocked and free to release the hammer and the slide will be free to move back.

On squeezing the trigger, the sear is moved and the released hammer strikes the firing pin which transmits the blow to the primer of the cartridge. The pressure of the gases generated in the barrel by the explosion of the powder in the cartridge is exerted in a forward direction against the bullet, driving it through the bore, and in a rearward direction against the face of the slide, driving the latter and the barrel to the rear together, The downward swinging movement of the barrel unlocks it from the slide and the barrel is then stopped in its lowest position. The slide continues to move to the rear, opening the breech, cocking the hammer, extracting and ejecting the empty shell, and compressing the recoil spring until the slide reaches its rearmost position when another cartridge is raised in front of it and forced into the chamber of the barrel by the return movement of the slide under pressure of the recoil spring.

The weight and consequently the inertia of the slide augmented by those of the barrel are so many times greater than the weight and inertia of the bullet that the latter has been given its maximum velocity and has been driven from the muzzle of the barrel before the slide and barrel have recoiled to the point where the barrel commences its W'llocking movement. This construction therefore delays the opening of the breech of the barrel until after the bullet has left the muzzle and therefore practically prevents the escape of any of the powder gases to the rear after the breech has been opened. This factor of safety is further increased by the tension of the recoil spring and mainspring, both of which oppose the rearward movement of the slide.

While the comparatively great weight of the slide ot the pistol insures safety against premature opening of the breech, it also insures operation of the pistol because at the point of. the rearward opening movement where the barrel is unlocked and stopped the heavy slide has attained a momentum which is sufficient to carry it through its complete opening movement and makes the pistol ready for another shot.

When the magazine has been emptied, the pawl-shaped slide stop is raised by the magazine follower under action of the magazine spring into the front recess on the lower left side of the slide, thereby locking the slide in the open position and serving as an indicator to remind the shooter that the empty magazine must be replaced by a loaded one before the firing can be continued, Pressure 1,1pon the magazine catch quickly releases the empty magazine from the receiver and permits the insertion of a loaded magazine.

To release the slide from the open position, it is only necessary to press upon the thumbpiece of the slide stop, then the slide will go forward to its closed position, carrying a cartridge from the previously inserted magazine into the barrel and making the pistol ready for firin1 again.

d. Care and cleaning.

To clean the pistol rub it with a rag which has been lightly oiled and then clean with a perfectly dry rag. Swab the bore with an oily flannel patch and then with a perfectly dry one. Dust out all crevices with a small, clean brush. Immediately after cleaning, to protect the pistol swab the bore thoroughly with a flannel patch saturated with sperm oil, wipe over all metal parts with an oily rag, applying a few drops of light oil (sperm oil) to all cams and working surfaces of the mechanism.

After cleaning and protecting the pistol, place it in the pistol rack without any covering whatever. The use of canvas or similar covers is prohibited, as they collect moisture and rust the metal parts. After firing, do not oil the bore until it has been thoroughly cleaned. This must be done not later than the evening of the day on which the pistol is fired. Thereafter it will be cleaned and oiled each day for at least the next three succeeding days. To clean the bore after firing, first remove the slide and barrel, insert the muzzle of the barrel in a vessel containing hot water and issue soap, hot water alone, or cold water; the cleaning rod with a cloth patch assembled is inserted in the breech and moved forward and back for about 1 minute, pumping the water in and out of the bore.

When the bore is wet, a brass or bronze wire brush, if available, should be run all the way through the bore, then all the way back three or four times. Water should again be pumped through the bore. Them wipe the cleaning rod dry, remove the barrel from the water, and using dry, clean flannel patches thoroughly swab the bore until it is perfectly dry and clean. Examine the bore carefully for metal fouling. Saturate a clean flannel patch with sperm oil and swab the bore and chamber with the patch, making certain that the bore and all metal parts of the pistol are covered with a thin coat of oil.

4. Carbine. The carbine has been recently adopted for use by certain infantry personnel. Data on this weapon is not available at this printing.

5. Smoke.

The tactical use of smoke is to provide a screen which will prevent enemy observation and aimed fire. Smoke may be used, on either the offensive or the defensive, to reduce the effectiveness of the enemy's weapons or to hide movements of our own troops. Screening smokes ( as distinguished from the toxic smokes used by the chemical warfare service) are produced by three mediums. These are:

Sulphur trioxide solution (FS).
This is a liquid used in airplane spray and artillery or mortar shell. It changes to a dense white smoke on contact with the air. While not injurious, it renders food and water unfit for use and, where moisture is present, has an active corrosive effect on metal.

HC mixture.
This is used in smoke pots or candles for training. An acrid white smoke is produced by burning the munition.

White phosphorus (W. P.).
From the infantry standpoint, this is the only really important smoke-producing agent. It is used in shell, primarily for the screening smoke produced, but it also has a casualty-producing effect as the particles scattered by the shell burst produce severe burns. Loaded in artillery or mortar shell and dispersed as a solid, it changes to flame and white smoke on contact with the air.

Organically the infantry is equipped with only one smoke-producing weapon, the 81-mm mortar when firing shell loaded with white phosphorus. The smoke pot, H .C. M-1, which replaced both the smoke-producing hand grenade and the smoke candle for in fan try use, may be issued as required when the necessity for screening our own position arises. However, the infantry unit commander may call upon more effective smoke-producing agencies. These are: The artillery, which is provided with smoke shell of all calibers; the chemical warfare service, which is equipped with mortars that are highly effective for producing smoke screens; and the air corps, which is the most rapid and effective agency for screening large areas.

Smoke is a tactical weapon which must be employed with caution. Generally, the indiscriminate use of smoke must be prevented, and this will normally be accomplished by restricting its use to the battalion and higher units. The reason for this is that a squad, or platoon, using smoke to conceal a small maneuver, may accomplish this result very effectively but might at the same ti.me obscure the target of all the machine guns of the battalion.

QUESTIONS

1	What common characteristic exercises a restrictive influence on infantry weapons?
2	How are grenades classified generally?
3	What are the three general types of hand grenades used in our service?
4	Describe the Mk II hand grenade.
5	What are the general characteristics of grenades?
6	What is the tactical use of the hand grenade?
7	Describe the automatic pistol.
8	What is the tactical use of the automatic pistol?
9	What is the tactical use of smoke?
10	What three mediums are used to produce screening smoke?
11	With what organic smoke-producing weapon is the infantry equipped?
12	What other smoke-producing agencies are available on call by the infantry commander?

CHAPTER II

THE LIGHT MACHINE GUN

6. Characteristics.

a. General. The infantry light machine gun is the Browning Machine Gun, caliber .30, H.B. M-l919 A4. (The letters HB in this official designation mean "Heavy Barrel"). It must not be confused with the modified Browning automatic rifle, which has been used as a substitute light machine gun and which is retained in the armament of the infantry platoon. The A4 light machine gun (see Plate 10) is recoil-operated, belt fed and air-cooled.

b. Principle of operation. In recoil operation the rearward force of the expanding powder gas (kick) is utilized to perform mechanically the operations of unlocking the breech, extracting and ejecting the empty cartridge case and feeding in a new round, as well as cocking, locking and firing. The receiver mechanism of the light machine gun is identical, for all practical purposes, with that of the heavy Browning Machine Gun M-1917.

c. Cooling system.
The M-l919 A4 gun is provided with a heavy barrel which is exposed to the air. In other words, it is "air cooled", Remember this for comparison later with the heavier water-cooled machine gun, as this characteristic i.e., a less efficient cooling system, makes the light machine gun less capable of rapid, long sustained fire. The-air cooled heavy barrel will keep the A4 gun at operating temperature for about 30 minutes at a rate of fire of about 60 rounds per minute. A rate of 150 rounds per minute can be maintained for about 15 minutes, but fire at faster rates can be maintained only for short periods.

d. Belt.
Woven fabric belts of a capacity of 150 rounds per belt and with brass strips at each end to facilitate loading are normally used with the light machine gun. e. Sights.
The front sight is of the post and blade type. It can be folded down, for convenience in packing. The rear sight is of the conventional leaf type, somewhat similar to that used on the Springfield rifle. However, both the elevation and windage adjustments are provided with a mil click device.

f. Mounting.
The infantry light machine gun is mounted on the light machine gun tripod M2. This simple tripod provides a stable mount and gives maximum strength and rigidly consistent with desired light weight. The M2 tripod consists of three tubular steel legs articulating for a tripod head, the two trail legs being joined and supported by a traversing bar, forming a simple A-truss and serving as a rear support for the mounted gun. The tripod head and short front Leg provide the front support.

g. General data.

Number	Characteristics	Data
1	Weight of gun	28 pounds
2	Weight of gun, with pintle and elevating mechanism	31 1/4 pounds
3	Weight of tripod mount, M2	14.11 pounds
4	Length of barrel	24 inches
5	Cyclic rate of fire ( rounds per minute)	400-550
6	Maximum usable rate of fire ( rounds per minute)	150
7	Sight graduated to (yards)	2,400
8	Muzzle velocity (M2 ball cartridge) in feet per second	2,700

PLATE 10 - The Light Machine Gun in Firing Position.

7. Powers and Limitations.
The light machine gun is relatively mobile. Its crew can maintain the march rate of a rifleman but cannot move at the high speed of the individual rifleman. It delivers a large volume of fire rapidly and accurately. The capacity of the gun on its ground mount for overhead, indirect fire, and antiaircraft fires is limited. Its characteristics fit it for use in the attack for the close support of the smaller infantry units by flanking action; in defense, to supplement the action of heavy machine guns. Within midrange its accuracy is about that of the heavy machine gun. Like other crew served \v'capons these guns and their ammunition are transported by motor carriers or pack animals but require man-handling in combat. The motor carriers keep ammunition as close to the guns as practicable.

8. Tactical Use.

a. General.
The light machine gun is a rifle company weapon. The light machine gun section is part of the weapons platoon. It consists of a head quarters and two light machine gun squads, each composed of a corporal and four privates. The squad operates one light machine gun. The corporal is the squad leader and the four privates are assigned as gunner, assistant gunner and ammunition carriers. When che gun is moved by hand the gunner carries the tripod and one chest of ammunition; the assistant gunner carries the gun, a pair of asbestos mittens and one chest of ammunition; one ammunition carrier carries a spare barrel with extension, a spare parts chest and one chest of ammunition; the second ammunition carrier carries two chests of ammunition.

This gun is a direct fire weapon, designed to deliver automatic fire at close and mid ranges. As it is a supporting weapon it must be kept well forward so that the gun crew can see both their targets and the location of their own front line. The flat trajectory fire of infantry, and particularly that of the automatic weapons, is highly destructive against unsheltered personnel, and if wel1 directed it will inflict severe losses on exposed troops and pin them to the ground or drive them to cover. Against troops under cover the Bat trajectory fire of light machine guns has little effect except to neutralize their fire and to keep them under cover.

b. Light machine guns in attack.
During the attack, light machine guns are employed to fire through gaps in depth across the front of their own company or elements thereof, or to fire from a flank across the front of adjacent companies. If no suitable mission of this nature presents itself, they are held ready to make a rapid advance to positions from which they can deliver flanking fire.

The light machine guns of a company are transported by one of the weapons carriers assigned the weapons platoon as far forward as the battalion assembly area. Until this area is reached the carrier usually moves with the battalion transport. On the approach march the weapons carrier may continue to move with the battalion transport, or it may accompany the weapons platoon. If the terrain is broken or rugged, forcing motor vehicles to move slowly, the carrier may move with the foot elements, but on level ground it is usually best to have it follow the foot elements by bounds. When action appears imminent, light machine guns and ammunition are removed from the carrier and are transported by hand under direction of the section and squad leaders.

In combat, the section leader directs the fire of the section and assigns targets or sectors of fire and position areas, and regulates the displacement of the weapons. The squad leader is charged with fire control and fire discipline, the preparation and occupation of positions, the movement of the squad to designated position areas, entrenchment, and camouflage.

In the attack the company organizes a base of fire. The light machine gun section is assigned a sector of fire or target or targets and an initial position area or it is assigned positions from which it will prepare to advance with the attacking echelon.

Where tanks lead an attack, the section is assigned a sector of fire and an emplacement in accordance with the battalion plan of supporting fires. When an open field of fire is available on the flank of the company base of fire, the section is ordinarily assigned a target or targets, or a fire sector. When the company occupies a position to the rearward of an adjacent company, the light machine guns are assigned initial positions in the adjacent zone for the delivery of flanking fire on targets assigned or which may develop in the course of the advance 0£ rifle platoons.

The action of the section may be regulated by the assignment of a line of advance in support of the attacking echelon; or it may be held in a position of readiness to await the development of a situation which will permit its employment for the delivery of flanking fires.

Effective use of the light machine guns demands that the section leader be constantly in touch with the situation on the flanks of the company. When a position no longer affords an effective field of fire and other factors of the situation permit, the section leader effects a displacement of his unit.

The state of ammunition supply has an important bearing on the decision of the section leader to effect a displacement. With a depleted ammunition supply, it is better to effect replenishment before moving into an area where combat conditions make resupply impracticable.

c. Light machine guns in defense.
The close defense of a position is based largely upon the reciprocal flanking fire of machine guns. Except for the limitation on duration of fire imposed by the relatively inefficient cooling system, the light machine gun is almost as effective as the heavy machine gun for this purpose. Light machine guns, like other rifle company weapons, open fire when the enemy arrives within ranges which compel him to lift the fuc of his artillery to avoid hitting or endangering his own infantry.

When a defensive position is occupied at the conclusion of an attack or of an approach march, the light machine guns are located on a base of fire by the company commander and the section assigned sectors of fire covering the front of the position. Fire missions are assigned by the company commander.


QUESTIONS

1	How is our present light machine gun designated officially?
2	What is its principle of operation? Describe.
3	What is the cooling system?
4	What effect does the method of cooling have on the rate of fire and the time fire can be maintained?
5	With what type of front sight is the light machine gun equipped?
6	Give the weight of the gun? The tripod?
7	What arc the powers and limitations of the light machine gun?
8	What is this gun's place in the infantry organization?
9	For what tactical use was the light machine gun designed?
10	Describe the general employment (mission) of light machine guns in attack.
11	What is the principal function of light machine guns in defense?
12	When do defensive light machine guns open fire?

CHAPTER III

THE 60-MM MORTAR

9. Characteristics.

a. General.
The 60-mm mortar (M2) (Plate 11) is a smooth bore, muzzle-loading, high-trajectory weapon. The mortar consists of a barrel, base cap and firing pin, all assembled into one unit (see Plate 11). The mount consists of two units, the bipod and the base plate. The barrel is bored smooth and carefully finished in interior dimensions and surfaces. Clamp position marks are painted on the barrel to indicate the position of the mortar clamp for different elevations. The base cap screws on to and closes the breech end of the mortar. A spherical projection provides a locking device for securing the barrel to the base plate. The base cap is bored and threaded axially to receive the firing pin, which, when in place, is stationary with its point protruding into the tube.

The barrel is attached to the base plate by inserting the spherical projection into the base plate socket and then closing the locking lever.

The bipod consists of the legs, the elevating mechanism and the traversing mechanism. The right leg contains no moving parts but the left leg assembly is provided with an adjusting screw which will lengthen or shorten the leg as required on uneven ground to keep the traversing screw in a horizontal position.

The M4 sight, which is also the standard sight for the 81-mm mortar, is of the collimator type, i.e., its basic laying device is an opaque sighting tube containing a vertical white line with a zero deflection setting. This line establishes a vertical plane in the field of view parallel to the plane of fire. The line of aim is established by aiming stakes, which are improvised as required, or by an aiming point if it is impossible to use stakes.

The ammunition for this mortar consists of shell, somewhat similar in appearance to an airplane bomb. A high explosive (Plate 12) and a practice shell are authorized for issue. The shell is propelled by the gas generated by the firing of an ignition cartridge, which is fitted into the base of the shell, and the combustion of bundles of sheet powder attached to the base of the shell between the blades of the fin. The powder bundles are ignited by the ignition cartridge. The full propelling charge consists of four equal powder increments. When the full charge is not required, one or more of the increments are removed. The shell weighs approximately three pounds (2.96, lbs.)


PLATE 11 - The 60-mm Mortar in Firing Position.

The shell is exploded upon ground impact by its detonating fuze, which is prepared for firing by removing the cotter pin (safety wire.)

b. General data.

Weights:

Mortar ..... . .... . . .. . .. . . ... ........ pound ... 42
Mount ........................... .... ......... do ... .. 29.2
Bipod ...................... ... .... .......... do ... .. 16.4
Base plate ... . ................ . . .......... do ... .. 12.8
Overall length ...................... . ........ inches . . 28.6
Elevations,- approximate .......... ...... .. .. degrees .. 40 to 85
Mortar clamp position A .... . ...... ... ...... do . . . . 40 to 65
Mortar clamp position B . . . .. ....... . ..... do .. . .. 45 to 70
Mortar clamp position C ..... . ..... . .. . ... do . . ... 50 to 85
Traverse, right or left, approximate .. . . . .. mils ..... 70
One turn of handwheel, approximate ..... . . . . do . ..... 10

Rate of fire:

Maximum rounds ........... . ......... . . . ... per minute .. 30 to 35
Normal rounds ............ . .. .. . . . ..... . do .......... 18

Range, approximate:

Shell, HE	yards 100 to 1935
Shell, Practice

10. Powers and Limitations.

The 60-mm mortar is designed to carry out all the high-angle-fire missions of the rifle company. Because of its high, curved trajectory it is particularly effective against targets which arc defiladed from the fire of rifles and machine guns, and because of this curved trajectory it is adapted to fire from masked positions, and is not restricted by the safety precautions imposed on flat trajectory weapons when firing over the heads of friendly troops. Thus the mortar can render close and effective support by firing over the heads of attacking platoons until the riflemen ate close enough to the hostile position to deliver the final assault.

It is accurate enough to engage effectively enemy machine guns that have been definitely located. The maximum effective range is 1,000 yards, and the distance from the mortar to our own front line troops should not exceed 500 yards. Accuracy of fire diminishes as the range increases. Because of its low relief the 60-mm mortar is easy to conceal and requires little cover. It is light and correspondingly mobile. However, mortar ammunition is heavy, difficult to supply in combat, and must be economized in offensive operations. The effective bursting radius of the shell is about 15 yards; casualty producing fragments carry much farther.


PLATE 12 - Shell, HE, M49A1 .

11. Tactical Use.

(a) Organization of the 60-mm mortar section. Like the light machine gun, the 60-mm mortar is a crew served weapon of the rifle company. The 60-mm mortar section of the rifle company weapons platoon consists of a headquarters and three mortar squads, Each mortar squad is composed of a corporal and four privates.

The corporal is squad leader, number 1 is gunner, number 2 is assistant gunner, and numbers 3 and 4 carry ammunition. Each squad serves one 60-mm mortar, The mortar section has the use of one of the two ½-ton weapons carriers (trucks) furnished the weapons platoon, Sixty rounds of ammunition per mortar are transported on the weapons carrier which is also provided with one Browning automatic rifle for antiaircraft defense. Additional ammunition is carried on the ammunition trains of higher echelons.

b. The 60-mm mortars in attack,
The 60-mm mortars of the weapons platoon are transported during the advance and approach march as described for the light machine guns in the previous chapter, The section leader receives his orders and instructions from the platoon leader who selects the position area. The squad leaders reconnoiter and select the exact position for their mortars.

The location of firing positions is influenced by many factors, including the location, if targets and friendly front-line troops, requirements of cover and observation, fire missions, assigned by the platoon leader, and facility of ammunition supply. In all cases the mortar positions must be within effective range of the targets and afford observation of the targets and friendly front-line troops. Effort should be made to keep the mortar as close to the leading echelon as the terrain and the situation permit; Wherever practicable, mortars fire from fully defiladed positions. On flat terrain, however, the occupation of open positions is sometimes necessary to bring the mortars into proper relation to their targets and the front-line troops. The low relief of the piece permits it to utilize the cover afforded by minor terrain features such as shell holes, ditches, hillocks, small rises. Wherever permitted by the foregoing considerations, the mortar emplacements should be within voice or arm-and-hand signaling distance from the company command post.

Positions permitting covered approach from the rear greatly facilitate ammunition supply and increase the value of the mortar as a supporting weapon, This consideration, however, must not be given precedence over the requirement of proper location with reference to the target and the front-line troops.

In locating the mortar position, advantage is taken of natural vegetation to conceal the piece from observation. Natural or artificial means are employed to camouflage the weapon and its emplacement. Where the situation indicates a prolonged occupation of its position, alternate mortar emplacements are selected.

The squad leader controls the fire of his mortar from an observation post at or near the firing position of the piece. The section or platoon leader exercises immediate fire direction and concentrates or distributes the fire by assignment of targets or sectors of fire.

The principal duty of the section leader is to observe closely the rifle troops and regulate the movement and positions of the mortar squads in accordance with the action and changing situation of the rifle elements. Prior to displacement, a sector of fire of target area is assigned to each squad; the squad leaders take as primary targets those included in their assigned target areas or sectors and as secondary those appearing outside their sectors or target areas. They regulate their fires in accordance with the situation and the needs of the attacking echelon.

The advance of the mortars is so regulated as to enable them to respond instantly to the needs of the riBe platoons and place prompt and effective fire on targets of opportunity. Their fire allows the riflemen to maneuver more freely, advance close to the enemy, and prepare for assault. They are accurate enough to put hostile automatic weapons out of action and neutralize isolated resistance. Thus they constitute the companies most effective supporting weapon in the attack.

c. The 60-mm mortar in defense.
In defense each mortar squad is assigned a primary target area and may be assigned secondary target areas. Target areas are usually about 50 by 50 yards. They cover gaps in the final protective lines of machine guns in the company defensive sector or defiladcd approaches to the positions not covered by artillery or by the battalion supporting weapons. Fire is opened on signal prescribed by the company commander or on orders of the rifle platoon leader. On signal for the opening of final protective fires, mortars fire on their primary· target areas. When not actually engaged in firing or in preparing to fire on another target, the mortar is laid to fire on its primary target area. A supply of mortar ammunition is usually dumped in a covered location convenient to the mortar positions. From this location it is carried to the mortar by the ammunition carriers of the squad.

Mortar emplacements should be within arm-and-hand signaling distance of the post of the commander under whose direction the mortars are operating (rifle platoon or weapons platoon commander).

QUESTIONS

1	Give the three distinguishing characteristics of infantry mortars.
2	What are the component parts of the mortar? Of the mount?
3	Describe the 60-mm mortar shell.
4	What is the range? Weight of projectile? Rate of fire?
5	For what combat function was the 60-mm mortar designed?
6	What arc the powers and limitations of this mortar?
7	Describe the organization of the mortar section.
8	How is the mortar transported in combat?
9	Describe a satisfactory mortar position.
10	Who selects the exact firing position for each mortar?
11	State generally the actions of the mortar squad in attack.
12	Discuss the actions of the mortar squad in defense.

CHAPTER IV

CALIBER .30 MACHINE GUN (HEAVY), AND 81-MM MORTAR

12. The Cal. .30 Machine Gun (Heavy).

a. Description. The Browning machine gun, caliber .30 Ml917, (Plate 13) now usually referred to as the heavy machine gun, is recoil operated, belt fed and water cooled. Its operating principles are practically identical with those of the light machine gun described in Chapter II, the cssentid difference, being in the cooling system. Whereas the light machine gun depends for cooling on the heat radiation of a comparatively heavy barrel, in the heavy gun the barrel is surrounded by a water jacket which holds about seven pints of water. The water prevents the barrel from becoming overheated during prolonged firing at a rapid rate. The feed belt of woven fabric is similar to the light machine gun belt, but it contains 250 rounds.


PLATE 13 - Browning Machine Gun, Caliber .30 M1917 (Water Cooled).

b. Sights. The front sight is of the conventional blade type. The leaf rear sight (Ml) is adjustable for windage, and drift is automatically compensated for by the construction of the sight, as in the rear sight of the Springfield rifle. The sight is graduated in yards, for range, and in mils for windage or deflection. The latter system of graduation provides a means of laying off small angles.

c. This machine gun is mounted on the M1917Al tripod; larger, heavier and much more stable than the mount of the light machine gun. This tripod consists of a central socket, to which arc attached three legs which may be clamped independently in various positions to compensate for uneven or sloping ground. Adjustment of the rear leg, which is the longest, establishes the height of the gun. A traversing dial, seated on top of the socket, provides for the accurate measurement of any angle in the 6400 mils of the azimuth circle. The assembly includes a cradle mounting for the gun which permits large changes in elevation to be made rapidly. The elevating and traversing mechanism, housed in the rear end of the cradle frame, provide mechanical means for chan&ing elevation and deflection in single mil increments.

d. Genera / data.

Weight, gun with water jacket empty, (pounds) 33½
Weight, gun with water jacket. filled, (pounds) 40¾
Weight, tripod (pounds) 51
Weight, bdt, filled, in chest (pounds) 20½
Length of barrel (inches) 24
Sight graduated to (yards) 3400
Maximum rate of Ii.re (shot per min.) 400-525
Muzzle velocity (theoretical) (fc.et per second) 2700
Usable range (yards) 3500

e. Powers and /imitations.

The machine gun is a crew operated weapon. Because of its characteristics of a stable mount and an effective cooling system, it is capable of delivering a great volume of accurate, sustained small-arms fire. Its cyclic rate, that is, the rate of fire which results if the trigger is held back and the gun permitted to fire continuously, averages about 450 rounds per minute. However, effective lire is delivered in bursts of 6 to 20 rounds; with manipulation and frequent re-aiming of the gun, and as a result its maximum effective rate of fire is about 250 rounds per minute. Its stable mount permits it to be laid for the accurate delivery of fire in darkness, fog, or smoke; or for fire over the heads of friendly troops and at targets which are invisible &om the gun position. Although its weight is considerable it has the essential basic characteri5tics of all infantry weapons, that is, it can be broken down into one-man loads, or "manhandled" by three men, to accompany and support the rifleman.

Its most favorable target is personnel in the open, but it is used effectively against lowBying hostile aircraft. With the armor-piercing bullet it is effective against Lightly armored vehicles. It may be used against enemy tanks at close and mid range for harassing purposes. It is easily concealed, and, while the characteristic sound of its firing is instantly recognizable, it is hard to locate.

f. Tactical use.
The heavy machine gun squad consists of: 1 corporal; 3 privates, composing the gun crew; 3 privates as ammunition and water carriers, and l private as chauffeur. The gun crew consists of the minimum number of men required to operate the weapon- 1 gunner, 1 assistant gunner, and 1 ammunition and water carrier. In addition to its one machine gun the squad is equipped with 4 water chests, 1 chest of spare parts, and 27 ammunition chests each containing a belt of 250 rounds. This makes a total weight load (gun and equipment) of approximately 758 pounds. One ½-ton truck, designated as the weapons carrier, is provided for the transportation of the gun and equipment. AlI members of the squad arc armed with a pistol, except the chauffeur, who carries a rifle.

Two squads and a section headquarters constitute a section. The machine gun platoon of the heavy weapons company of the infantry battalion (rifle) is made up of a platoon headquarters and two sections. The student should bear in mind the fact that the cal. 30 heavy machine gua is a battalion weapon, in distinction to the light machine gun, which is a company weapon primarily. The machine gun, with ammunition and equipment, is normally transported on its weapons carrier. When the carrier moves with its squad, only the chauffeur rides on the vehicle. Normally the foot and motor elements of a command march separately in route column. In marching with the foot elements the carrier may either move with the assembled motor transportation at the rear of the foot column and advance by bound, rorh one covered position to another; or it may move in the column with its unit. Where terrain or the road net permits, carriers and foot clements may move in close parallel columns. In an uncovered advance a deployed formation will usually be necessary. In this situation the company may move as a unit with its transport under company control. Carrier, may either move assembled immediately behind the foot clements or move with their squads.

The platoon transport corporal is in charge of the weapons carriers of his platoon and supervises the antiaircraft lire of the carrier guns. At the present time one Browning Automatic Rifle, caliber 30, Ml918A2, is provided each section of trucks for antiaircraft defense. The gunners of the machine gun squads operate these guns during route and approach march.

In the absence of motor transportation or during approach marches with observation or fire from the enemy position, the gun and its ammunition and equipment may be transported manually by the crew. The position of the squad may be varied because of terrain, hostile observation, or enemy fire. When advancing in conjunction with rifle troops, the unit should adopt the same formations as the riflemen, in order to conceal its identity as a machine gun unit.

The chauffeur remains with the weapons carrier at all times. In the attack the heavy machine guns execute long range overhead fires and antiaircraft missions and protect the Banks of advancing rifle units against counterattack. Advancing by echelon, they extend in depth the fire power of the attacking riflemen. Io the defense, the heavy machine guns arc distributed throughout the position. Those sited for close defense of the main line of resistance are usually located from 50 to 200 yard, in rear thereof. Machine guns covering the main line of resistance open fire when the enemy arrives within ranges which compel them to lift the fire of his artillery to rearward areas. If the enemy succeeds in effecting a close approach to the main line of resistance, all machine guns fire, the rear guns firing overhead fire. Machine gun crews take cover against the attack of tanks, but open fire with armor-piercing ammunition againsL lightly armored vehicles.

13. 81-mm Mortar. (Plate 15.)

a. Characteristics. The 81-mm mortar is the big brother of the 60-mm mortar previously described, and is one of the most important and probably the most powerful weapons used by the infantry. It is a smooth bore, muzzle-loading, high-angle-fire weapon, very similar, except as to size, to its smaller contemporary. It is assembled in three parts- mortar, bi-pod and base plate. The mortar is composed of a barrel, (tube), base cap aod firing pin. The bi-pod consists of the leg assembly and the elevating and traversing mechanism assemblies. The base plate is one solid unit. When the mortar is set up for use the mortar itself is attached to the bi-pod by means of a mortar clamp, and locked to the base plate by injecting the spherical projection of the base cap into one of the three base plate sockets and rotating the mortar 90°.

The barrel is smooth bored and carefully finished in interior dimensions and surfaces. A flat surface is formed on the muzzle end of the barrel as a scat for a quadrant. Clamp position marks arc painted on the barrel to indicate the position of the mortar clamp relative to elevation.

The base cap is hollowed and threaded to screw on the barrel, thereby closing the breech end of the mortar. It terminates in a spherical projection, flattened on two sides, which fits into and locks in the socket of the base plate. The base cap is bored and threaded axially to receive the firing pin which, to prevent gas leakage, is screwed tightly into the base cap against a shoulder. When in place, the firing pin is held stationary with its point protruding through the base cap into the tube. The mortar serial number is on the base cap.

The bi-pod leg assembly consists of tubular steel legs mounted on the trunnions of tl1e gear case by a compass joint. The legs terminate in feet with spikes. The spread of the legs is limited by an adjustable chain fastening. A spring is interposed between the right-hand end of the chain and the right leg to relieve the legs of shock during firing.

The left leg carries a cross-leveling mechanism which consists of a sliding bracket connected with the guide tube by a connecting rod. A movement of the sliding bracket up or down is transmitted to the mortar through the connecting rod, the elevating mechanism assembly, and the traversing mechanism assembly, causing a corresponding movement of the mortar. Thus the mortar may be cross-leveled by moving the sliding bracket. The leveling process can be completed accurately by rotating a knurled adjusting nut on the upper part of the leg. When accurately cross-leveled, the movable pans of the cross-leveling mechanism arc locked in position by rotating the fluted locking nut.

The right leg contains no moving parts. The shock absorbers arc designed to stabilize the mortar and mount during firing. They permit movement between the yoke and the clamp assembly and arc countered by the resistance of the coil compression springs which arc mounted in the shock absorber retainers of the saddle.




PLATE 14 - The 81-mm Mortar.

The mortar clamp, by means of which the barrel is clamped to the bi-pod, is in two sections. The lower section, called the saddle, consists of the lower half of the clamping collar and two shock .absorber retainers with locking screws. The upper section consists of the upper half of the clamping collar. The two halves of the clamping collar are hinged and can be locked tightly together by the clamp bolt. When so secured about the barrel of the mortar, they lock it firmly to the bi-pod.

The base plate consists of a pressed steel body to which are welded, a series of ribs and braces, a front flange, three loops, two handle plates, and the socket. The socket carries three seats for the spherical end of the base cap of the mortar. These seats are placed vertically with respect to the axis of the bore when the mortar is mounted.

The 81-mm mortar is aimed by means of aiming posts and the sight. The weapon is provided with posts of two sizes: the MS, 2 feet long, and the M6, 6 feet long. The sight, M4, includes a collimator (an op.ique sighting tube containing a vertical white line), elevating and lateral deflection mechanisms, and longitudinal and cross levels. These are supported by a bracket with a dovetailed base which fits into a slot in the mortar yoke and latches in place.

General data.

Weight:

Mortar and mount ................. ..........	(pounds) ...	136.0
Mortar ........................... ... ......	do .. . ....	44.5
Mount ........................... ... . ... .	do . . . ...	91.5
Bipod .......................... .... .. ...	do .. . ....	46.5
Base plate ....................... ... . . .	do . . . ...	45.0
Over-all length of mortar ............. .. ..	(inches ) ..	49.5
Elevations (approximate) ............. ......	(degrees) ..	40 to 85
Mortar clamp positioa A ........... . . . ..	do .. . ....	40 to 70
Mortar clamp position B ........... .. .... .	do .. . ....	50 to 80
Mortar clamp position C ........... . . ... .	do . . . ...	55 to 85
Traverse, right or left (approximate) .......	(mils) .....	65
One turn of handwheel (approximate) .........	do ... .....	12

Rate of fire, rounds per minute:

Maximum . . . . . . . . . . . . . . . . . .. . . . . . . . 30 to 35 Normal . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Range (approximate).

HE Shell:

6.87 pounds .........................................	(yard,)....	1,000 to 3,290
10.75 pounds ........................................	do.........	300 to 2655
15.05 pounds ........................................	do.........	100 to 1,275
Chemical shell, 11.4 pounds .........................	do.........	300 to 2,470

b. Powers and limitations.
The 81-mm mortar combines mobility and power in greater degree than any other supporting infantry weapon. It can take advantage of deep defilade and exercise wide choice in selection of positions. Its light shell has an explosive effect comparable to that of the 75-mm artillery projectile: its heavy shell is comparable to the 105-mm artillery projectile. Range is limited by the requirements of observation rather than the ballistic properties of the weapon. The light shell is used against pers0nnel; the heavy shell against material and emplacements.

Because of its stabilizing fins, 81-mm mortar ammunition, Plate 16, even though fired from a smooth bore mortar, is stable in flight and strikes nose end first. A point detonating impact type of fuze is fitted to the nose of the shell. The propelling charge, consisting of an ignition cartridge and propellant increments, is attached to the base end of the shell.

There are three shells for use with this weapon:

a light explosive shell;
a heavy explosive shell;
and a heavy smoke shell.

The light explosive shell has a useful range of 2000 yards. The range is, however, limited by observation rather than the ballistic properties of the piece. The heavy explosive shell used against material and emplacements has a maximum range of 1500 yards. The barrel, bi-pod, and base plate each weigh approximately 45 pounds. Compared with the 60-mm mortar, the 81-mm mortar has greater power and less mobility; its ammunition is heavier; and its adjustment of fire is comparatively slow because of the long time of flight of the projectile at the longer ranges; its rate of fire after adjustment and its other characteristics are approximately the same.

Mortars can more readily engage targets of opportunity than artillery and are more suitable for use against point targets. n,.cy can fire from almost any position into almost any position. The high, curved flight of the projectile makes it particularly suitable for overhead close support fire. Mortars are easy to conceal and cover, because they can fire from defilade.

c. Tactical use.
The 81-mm mortar squad consists of :

1 corporal and 7 privates. The corporal is squad leader; number 1 is gunner; number 2 is assistant gunner; numbers 3, 4, 5, and 6, are ammunition carriers. Number 7 is chauffeur.

The mortar section of the heavy weapons company consists of a section headquarters and two squads, The mortar platoon consists of a platoon headquarters and two sections. Each mortar squad serves one 81-mm mortar. The squad is equipped with a ½-ton truck as a weapons carrier. To provide communication between the observer, who adjusts fire, and the mortar position the squad has two-sound-power telephones and two reds each containing 400 yards of assault wire.


PLATE 15 - 81-mm Light Shell and Container.

The squad leader directs the squad in action and gives the initial fire order. No. l (gunner) sets the sights, lays the mortar and gives the command to fire. Number 3 (ammunition carrier) bands shell to No. 2 (assistant gunner) who takes it in both hands. While the latter holds the round, No. 3 extracts tha cotter pin (safety wire). Upon No. l's command FIRE, No. 2 starts the shell into the muzzle of the barrel. The remaining ammunition carriers supply ammunition to No. 3. The chauffeur drives the weapons carrier. The mortar is transported on the weapons carrier whenever the situation and terrain permit. It is usually so transported during route marches and the: weapons carrier ordinarily moves with the battalion transport. The carrier may, however, move either assembled with the heavy weapons company transport in rear of the marching elements of the company, or it may move individually with its squad. When the carrier moves with its squad in route column it carries no personnel other than the chauffeur. If the vehicle carries the automatic rifle allotted to the section for antiaircraft defense it will, when separated from its squad, carry one additional man in order to operate the weapon for antiaircraft defense.

In approach march the platoon leader of the 81-mm platoon commands the platoon as a unit. When the terrain permits rapid movement of the carrier, it follows the foot elements by bounds; otherwise it moves with them. When action appears imminent, the carrier moves into a previously reconnoitered off-carrier position, under the general direction of the mortar platoon leader. Off-carrier positions are selected at the moat advanced location that affords cover for the carrier and can be reached without undue exposure to hostile fire.

The foot clements of the squad move in approach march with the platoon. Gassed areas arc detoured where possible, and heavily shelled are crossed by section rushes. When action is imminent the mortar, equipment, and ammunition arc carried by hand. They are moved in this manner from the off-carrier position to the firing position area under direction of the section leader. The squad leader makes a detailed reconnaissance for the exact location of the mortar emplacement. The subsequent displacements of the mortar may be effected by a combination of manhandling and use of the weapons carrier. The carrier must be sufficiently close at hand during attack for the transport of the mortar in case of a rapid advance by the attacking echelon. Some manhandling is nearly always required by the terrain and the situation.

In attack mortars fire on definitely located point targets defiladed from the fire of flat-trajectory weapons. Area targets requiring zone fires arc artillery targets. The necessity of conserving ammunition supply demands careful discrimination of mortar targets from those pertaining to the: machine guns on the one hand and the artillery on the other. Targets especially suited to mortar fire include road cuts, railroad embankments, reverse slopes, entrenched heavy weapons.

The employment of mortars in support of a tank advance is exceptional. The hostile antitank weapons revealing themselves by flashes or muzzle blast are appropriate targets for flat-trajectory automatic fires. Mortar fire against antitank weapons is ordinarily limited to preparatory fires in conjunction with artillery, when ample ammunition is available. Mortar fires arc for the most part fires against personnel. The heavy shell is employed in destruction fires against enemy shelters and accessory defenses. Smoke shell is used to lay down a screen or to blind observation at a particular locality in enemy territory.

Mortars may be assigned missions supplementing artillery in preparatory fires. In defense mortars arc employed to cover dead spaces in the bands of machine gun fire in accordance with the battalion fire plan, and to fire on dcfiladcd areas where hostile forces might assemble for attack. These fires are coordinated with the barrage and counter preparation fires of artillery.

Each mortar is assigned primary and secondary targets. The primary target is the target included in the battalion final protective: fires. Secondary targets are numbered and assigned priority. They arc fired on command or signal. They may include targets in the sector of the battalion or in those of adjacent battalions. Targets in a lower priority may be engaged in emergency where no signal is received and no target in higher priority is presented.

QUESTIONS

1.	What is the essential difference between the caliber .30 M.G. (heavy) and the caliber .30 light machine gun?
2.	What are the two most important characteristics of the heavy machine gun?
3.	What is the maximum effective rate of fire of the heavy machine gun?
4.	What is its most favorable target?
5.	What is the place of this weapon in the infantry organization?
6.	Describe the tactical use of the heavy machine gun in attack? In defense?
7.	What are the characteristics of the 81-mm mortar?
8.	Describe its powers and limitations?
9.	What is the range of the 81-mm mortar?
10.	What is the principal use of the light shell? The heavy shell?
11.	How is the 81-mm mortar used tactically in attack? In defense?

CHAPTER V

GUNS AND HOWITZERS

14. The 37-mm Antitank Gun, M3.

a. Characteristics.
The 37-mm antitank gun, M3, (See Plate 16) is an antitank infantry weapon. It is a crew-operated weapon of the field gun type, which fires armor-piercing and high-explosive shells. The gun has a very flat trajectory due to its high muzzle velocity. It is a single shot weapon with a drop type breech block and is mounted on a carriage of the split-trail type, equipped with pneumatic tires. The weapon is towed by a light truck, which is designated as the prime mover. The carriage is designed for high speed movement both on Ioads and cross country.


PLATE 16 - The New 37-MM Antitank Gun.

The gun is provided with wheel segments which swing on the axle and serve to raise the tires off the ground to increase the stability of the carriage when in firing position. They are locked both in the firing and traveling positions by a spring actuated plunger. The telescope sight, M6, is a non-adjustable, non-magnifying telescope with an illuminated reticle ( see Plate 17), which is graduated for various ranges -and leads. The geometric and optical axis of the reticle, corresponding to the zero range, is marked by the upper dot just inside the 5-mil circle. The dot in the center of this circle indicates a range of 600 yards; two dots, representing 10-mil and 20-mil leads, are placed on each side of the center and are connected by short lines. The 1,200-yard range is indicated by the lowest point on the circle and is not otherwise marked.

The bottom dot in the reticle indicates a range of 1500 yards. The short lines at the top and bottom of the circle mark the vertical axis and have no other significance, Illumination for the reticle of the telescope, M6, is provided by a small Mazda lamp. The lamp socket is screwed into the forward projection of the telescope mount. Light from the lamp is admitted to the reticle through a window above the lamp in the mount and a similar window in the telescope, which is also positioned above the lamp. A cable and plug assembly is furnished for plugging into the lamp socket and the socket in the battery compartment of the tool case mounted on the shield. The current for the lamp is provided by two standard tubular flashlight cells which are contained in the battery compartment of the tool case. A switch at the case turns the lamp on and off.


PLATE 17 - Reticle of the Telescope Sight M6.

The telescope, M6 (sight) is used for all firing with the 37-mm antitank gun.

General data.

Weights, ammunition:

Complete round, armor-piercing	(pounds) . . . . . . . . . . . . . . . . . .	3.41
Projectile, armor-piercing	do . . . . . . . . . . . . . . . . . . . .	1.92
Complete round, high-explosive	do . . . . . . . . . . . . . . . . . . . .	2.72
Projectile, high-explosive	do . . . . .. . . . . . . . . . . . . . . .	1.23

Breech operation	Manual
Muzzle velocity, armor-piercing (f/s)	2600
Muzzle velocity, high-explosive (f/s)	2750

Maximum limits of elevation on carriage:

level, (degrees) .. . ... . . . . .. ........ . .. . ......... . .. . .. .	From plus 15 to minus 10
Maximum traverse, right, (degrees) . . . . . . . . . . . . . . . . . . . .	30
Maximum traverse, left, (Jegrees) . . . . . . . . . . . . . . . . . . . .	30
Weight, gun and carriage, firing position (pounds) . . . . . . . . . . . .	912
Normal recoil, (inches) . . . . . . . . . . . . . . . . . . . . . . . . .	20
Rate of fire (aimed shots per minute) . . . . . . . . . . . . . . . . . .	15 to 20 rounds

b. Powers and limitations.
The 37-mm antitank gun is very accurate and has a comparatively rapid rate of fire, 15 to 20 aimed shots per minute. Its heavy weight, 950 lbs. with carriage, makes it difficult to move by hand except for very short distances, and it is normally drawn by a small truck. Its armor-piercing Shell will penetrate 1 ½ inches of armor plate at 1000 yards if the impact occurs at 90° to the surface or not more than 20° therefrom. Its high-explosive shell is directive against personnel. The gun ha~ a low silhouette and is easy to conceal until it opens fire, when the muzzle blast and sharp distinctive report make it comparatively easy to locate.

c. Tactical use.
The 37-mm gun squad consists of a corporal and 5 privates, one of whom drives the truck (prime mover) which tows the gun and carries the squad, ammunition and accessories. The squad operates one 37-mm antitank gun. The individual gun is the fire unit. Fire is opened on orders of the gun commander. In exceptional cases, fire may be opened on orders of the section leader. The firepower of, each gun being in the hands of only one man, the gunner, fire orders are easily transmitted and control is simple.

The squad leader conducts the movements of the squad, supervises the placing of the gun in firing position, and in some cases selects the position itself. He acts as squad observer and as such designates the target, issues fire orders, and controls and adjusts the fire of the gun. He keeps the section leader informed as to the status of the ammunition supply.

Two gun squads and a section headquarters constitute an antitank section. The antitank platoon consists of a platoon headquarters, one rifle squad (for local protection) and two sections. The antitank company of the infantry regiment comprises a headquarters and three platoons. The truck (prime mover) is used to tow the 37-mm gun whenever the situation and terrain permit. Because of the difficulty of cross-country movement by hand, the prime mover should tow the gun to a cover position a short distance in rear of its firing position. In occupying the cover position, every effort is made to use covered routes and to minimize. movement in the vicinity. When operating over very difficult terrain the crew should dismount prepared to assist the vehicle forward when necessary. Under certain conditions it may be desirable to uncouple the gun from the prime mover.

When two or more avenues of approach must be secured and cannot be covered from one point, the gun may be held in readiness at a centrally located position of concealment and cover. It will remain there on the alert to move quickly to meet the hostile attack at whichever point it develops. Everything possible to insure timely employment of the gun is accomplished io advance, to include selection of positions and routes thereto, effective warning, and communications service.

When the gun has been uncoupled preparatory to use, the prime mover is usually directed by the squad leader to join the other platoon transport at a previously designated point, the limber point, or to move to the nearest available cover. These points will usually be within visual signaling distance from the firing position, the distance being determined by the terrain, the situation, and the length of time it is believed the gun will remain in position. After the prime mover is placed under cover, the chauffeur removes his rifle and carries it slung over his shoulder.

Movement by hand as much as 400 yards is slow and difficult. It will be resorted to only for short distances and only when it is impossible to use the prime mover. The gun crew (corporal and 4 men) can move the gun for a short distance across nearly any type of terrain, except ditches with steep banks. This movement, however, is not only slow, but will also require additional personnel if there is difficult terrain to cross. Fire positions are occupied by the gun in action to cover assigned sectors of fire or potential avenues of approach. In attack, positions on high ground with wide fields of fire and view are sought. Trucks are kept close at hand. Cover and concealment may have to be sacrificed to provide the best field of fire and to preserve the ability to move.

In defense, locations with maximum concealment and which cover definite avenues of approach are sought. Trucks may be sent well to the rear if necessary for effective cover. If the work can be concealed, an emplacement for the gun and foxholes for the crew should be dug.

The initial location of a 37-mm platoon supporting attacking rifle units is as close to those units as the available cover permits. The advance of the attacking echelon i.e followed by the 37-mm platoon which displaces, by bounds, to successive cover positions. As a general rule, displacement forward is impracticable until the attacking units have gained a terrain feature which can be utilized as cover for the antitank guns. Upon the capture of an objective, the guns are disposed to best protect the assaulting troops against tank counterattack.

In the defense antitank guns are assigned positions from with they can cover their sectors of fire or protect a designated unit. Usually time is available for the preparation of primary alternate, and supplementary positions.

In defense, time and the situation usually permit the preparation of a cover position, a primary (firing) position, alternate (firing) position, and a supplementary (firing) position.

A cover position is one in close proximity to the primary position which provide cover and concealment. In open terrain, artificial concealment is provided, When the observer, who remains near the primary position, signals an approaching target, the gun is moved rapidly to that position and is prepared tor action. The distance between the cover and firing positions is determined by the available cover and concealment and by the situation.

A primary position is one offering the best conditions for the accomplishment of the gun's mission. The gun must be in the primary position before the enemy tanks come within effective range.

An alternate position affords the same field of fire as the primary, but is located sufficiently far away (minimum of 40 yards), to provide protection against hostile fue registered on the primary positions. The squad leader makes the decision relative to the necessity for moving from the primary to the alternate position. A supplementary position is selected near the primary position for the purpose of covering a different area or avenue of approach. The selection and occupation of supplementary positions arc usually prescribed by the platoon leader.

Withdrawal under hostile fire during a tank attack is never permitted, However, short quick changes of position or the occupation of the alternate position may be necessary to facilitate firing.

15. The 37-mm Gun, M1916.

a. Characteristics.

The 37-mm gun, M1916, is a small, accurate, breech-loading, single-shot cannon which fires an explosive projectile weighing 1 ¼ pounds, Its maximum range is about 4000 yards, but its effective range, based on the distance at which the burst of its shell can be observed, is about 2,000 yards. The bursting radius of the high-explosive shell is five yards. This gun was originally designed for use as an anti-machine gun weapon and against enemy tanks.

The heavy armor of modern tanks is proof against the comparatively low velocity shell of this gun, and its role as an anti-machine gun weapon has been taken over by the powerful and accurate new mortars. The Ml916 37-mm gun is now classified as obsolete, but it is a fairly good training weapon as a substitute for the 37-mm antitank gun until this new weapon is available in quantity. The general design and mechanical construction of the MI916 gun arc quite similar to the new antitank gun, except that it has a shorter barrel and artillery wheels.

General data.

Weight of barrel and cradle group ............. . ... . . .	pounds . .	88
Weight of trails (complete tripod mount), about ..... ...	do . .. .	86
Weight of wheels and axle .................... . . . ... .	do . . . .	166
Weight of gun and carriage, complete ......... . .... . . .	do .. . .	340
Length of barrel ............................. . . . . . .	inches ..	29.133
Length of recoil .............. : .............. . . .. ...	do . . . .	7 to 10
Maximum anile of elevation ................. .. . . . . ...	degrees . .	21
Amount of traverse to right ..................... . .. . ..	do..... .	22
Amount of traverse to left ...................... .... .. .	do . . .	16
Diameter of wheels ........................................	inches.	37.5
Over~all length of vehicle ................................	do. . . .	75
Over-all width of vehicle, trails spread ..................	do .. . .	57
Over-all width of vehicle, trails closed ..................	do. . . .	39.25
Oil capaci ty of cradle . . . . .. .. . . . . .. . . .. ...	pints . .	2.75
Weight of ammunition chest, capacity 16 rounds (empty).....	approximatdy pounds.	8
Wc:ight of 1 round, HE shell ........... .. ... . ... .. ..	do ......	1.572
Wc:ight of 1 round, LE shc:ll .... . .. . .. . . ....... ..	do . . ..	1.435
Weight of chest containing 16 rounds HE shell .. . ... . ..	do .. . .	33.15
Weight of chest containing 16 rounds LE shell .... .... ...	do . . . .	30.96
Muzzle velocity, HE shell .... .... . .... . . . .. . . ...	feet per second ..	1276
Muzzle vclocity, LE shell .. .. ...... .. . . .. . . . .. .	do . . ..	1312
Rate of fire, maximum (aimed fire) . . .. . .. .. . . . ...	rounds per minute . .	25

b. Tactical use.
The 37-mm gun, Ml916, is a training weapon, used as a substitute for the 37-mm antitank gun. When so used, its tactical employment and powers and limitations should be assumed to be the same as those of the more modern weapon.

16, Howitzers.

a. General.
The Infantry has recently adopted the 75-mm howitzer, and the 105-mm howitzer as infantry weapons. These together with the 37-mm Antitank Gun, M3, provide the principal armament of the newly created cannon company of the infantry regiment.

b. The 75-mm howitzer.
This powerful weapon has an extreme range of 9,700 yards when firing Shell, HE (high explosive) with P D fuze, M48 (semi fixed), and 7,400 yards when firing the same shell with time-and-super quick fuze, M54 (semi fixed) . The maximum effective range for both kinds of ammunition is 85 percent of the extreme range. The fuzed projectile weighs 14.6 pounds, a complete round 18 pounds, and a complete round, packed, 22 pounds. The rate of fire of this weapon is three rounds per minute in prolonged firing and six in short bursts.

c. The 105-mm howitzer.
The 105-mm howitzer when firing Shell, Ml, with P D fuze, M48 (semi fixed) has an extreme range of 12,100 yards, and 8,700 yards when the same shell with the time-and-super quick fuze is being used. The maximum effective range is approximately 85 percent of the extreme range. The fuzed projectiles weigh 32.7 pounds, complete rounds 42 pounds, and complete rounds, packed, 50 pounds. The weapon is capable of being fired at the rate of two rounds per minute in prolonged firing and four per minute in short bursts.


PLATE 18 - The Caliber .50 Machine Gun.

17. The Browning Machine Gun, Caliber .50. (Plate 18.)

a. Description.
The antitank machine gun known as the Browning Machine Gun, Caliber .50, HB (flexible), M2, Ground will probably be used as an infantry weapon for some time to come and is for that reason included in this section. The weapon is equipped with machine gun tripod mount, caliber .50, M3. It is recoil operated, belt fed, and air cooled. The weapon has a high initial velocity, with adequate armor penetration at close and mid ranges. At an angle of impact of less than 20° from normal, armor-piercing ammunition will penetrate armor of about ¾-inch thickness at a maximum range of 500 yards.

The principles of operation are similar to other Browning machine guns previously described. The back plate assembly, however, has spade hand grips, the gun is so designed that by repositioning certain parts it may be fed either from the right or left aide, and a metallic disintegrating link belt is used instead of a fabric belt as on other Browning models.

b. Sights.
The gun is provided with a conventional front and rear sight, and a mount for a telescopic sight. The leaf of the rear sight is graduated to 2,600 yards. The range dial of the telescopic sight is graduated in yards from 100 to 3,000 yards; and in mils from O to 64.

The rear sight base is provided with an adjustable dovetail groove in which the telescopic sight, T-3, is mounted. This sight has a magnification of 3.25 power. The telescopic sight gives much greater accuracy and should be used whenever possible; that is, in the delivery of fire of precision on stationary ground targets and in fue on moving targets.

c. Mount.
The mount is a tripod, very similar in general design to that of the light machine gun, although, of course, much stronger and heavier.

d. General data.

Weights:

Gun (flexible) without barrel ..... . ... . ............ .	(pounds)......	54.38
Tripod mount, M3 ........... · ........ . ...............	do. .. .. . . . .	40.50
Pintlc and elevating gear (carried attached to receiver) ..	do. . . . . . . . .	4.00
Ammunition chest, empty .. ... .. .... ..... ........... .. ..	do .... .....	4.73
Belt of ammunition, 100 rounds ... . . . ... . . .. . . ... .	do. .. .... ..	30.80
Barrel ( 45 inch) .. · ... .... ............ . .. . . . . .. . .	do. . . . . . . . .	29.50
Capacity of ammunition chest, 1 belt .... .. ... . .......... . ..	(rounds) . . . . . .	100
Muzzle velocity : ............ .. ......... . .. . .......	(feet per se_cond) . . . . . .	2,660
Rate of fire, cyclic . ......... .. ...... · ... .. . . .. . .	(rounds per mrnute)... .. .	400-500

e. Powers and limitations.
The cal. 50 machine gun has high mobility and low relief as compared with otl1er antitank weapons (but by no means as compared with the other machine guns previously described). It can be manhandled for a considerable distance and can occupy firing positions unobtrusively. Weapon and crew occupy a small area and are easily concealed. The gun employs direct fire and engages ground targets only.

The caliber .50 machine gun is capable of firing from 400 to 500 rounds per minute, but since it is an air-cooled weapon such a high rate of automatic fire cannot be maintained continuously. Normally, the gun is fired in short bursts, but may be fired by rapid single shots and either type of fire may be continued for an appreciable length of time. With a cool gun a single burst of 100 to 150 rounds can be fired without overheating the barrel. The heavy- barrel retards overheating; added cooling is secured by the circulation of air around the breech, through slots in the barrel supports. f. Tactical use.
The heavy weapons company includes a caliber .50 machine gun platoon of two sections, each of two squads. Each squad operates one gun. Although a specialized weapon, the same general considerations as to tactical employment apply to this as to other supporting weapons. In the attack the guns arc located initially to prevent a sudden onrush of hostile tanks. Usually they arc held under cover near good positions which can be occupied promptly in case of need. Their firing positions cover the probable route of advance of hostile tanks.

As the action progresses, they advance if necessary to new positions which will enable them to continue this mission. Cal. .50 machine guns employ direct fire and c11gagc ground targct only. They always occupy open fire positions. When employed by section, each piece is so emplaced as to cover the sector assigned to the other in addition to its own. In view of their limitation to close and midrange missions they should, when practicable, be emplaced near the center of the sector of fire. There should be cover in the immediate 1rear of the firing position for occupancy by the weapon and crew prior to opening fire. Artificial cover should be constructed where natural cover is not available. In hastily occupied positions, cover for the carriers at short distance from the firing positions greatly facilitates ammunition supply.

e. The gun emplacements should be separated by sufficient distance to insure against simultaneous destruction by a single projectile but close enough in each section to permit of effective control by the section leader.

As the rifle units advance to the assault, the antitank weapons should be well forward, usually within close range of the hostile position. Displacement in this phase is usually off carrier. On the delivery of the assault the weapons move into the lines of the rifle units prepared for defense against mechanized counterattack. On the capture of objectives they immediately establish antitank security on the successive bases of fire. In the defense, cal. .50 machine guns are sited for close range defense of the main line of resistance. It is to be expected that tanks will lead the hostile attack, and the cal .50 machine guns withhold their fire until the enemy tanks arrive within close range of the main line of resistance. Against heavily armored tanks, their fire is directed principally against the track assemblies, as cal. .50 hits on these parts are more likely to have effect than on the stronger turrets or bodies.

Questions

1. What are the characteristics of the 37-mm antitank gun?
2. Describe the telescope sight M6.
3. Which dot in the reticle marks the optical axis of this sight? What elevation is indicated bv this dot?
4. What range is indicated by the bottom dot in the reticle?
5. How is the breech of the 37-mm antitank gun operated?
6. What is the total weight of the gun and carriage?
7. What is the rate of fire?
8. Describe the powers and limitations of the 37-mm antitank gun.
9. What is its place in the infantry organjzation?
10. Discuss its tactical use in attack. In defense.
11. What is the extreme range of the 75-mm howitzer?
12. How much does a complete round, packed, weigh?
13. What is the maximum effective range of the 105-mm howitzer when the M54 fuze is used?
14. What is the rate of fire for the 105-mm howitzer when being fired in short bursts?