GSP 1399 Theory of SAs PDF

i CONTENTS Section Subject Page Introduction 1 CHAPTER 1 – CLASSIFICATION OF SMALL ARMS 1...

i CONTENTS Section Subject Page Introduction 1 CHAPTER 1 – CLASSIFICATION OF SMALL ARMS 1 Classes by Use 3 2 Classes by Type of Functioning Cycle 6 CHAPTER 2 – DEFINITIONS 3 Definitions Relating to Weapons 8 4 Definitions Relating to the Motion of the Projectile 11 through the Air 5 Definitions Relating to Automatic Fire 16 6 Definitions concerning Anti-Tank Weapons and 20 Projectiles 7 Miscellaneous Definitions 21 CHAPTER 3 – OPERATING FUNCTIONS 8 General 23 9 Feeding 24 10 Chambering and Locking 28 11 Firing and Unlocking 29 12 Extracting and Ejecting 31 13 Cocking 33 CHAPTER 4 – DESIGN FEATURES OF SMALL ARMS AND THEIR AMMUNITION 14 Internal Ballistics 38 15 Ammunition 41  ii Section Subject Page CHAPTER 5 – SIGHTS 16 Types of Sights 43 17 Factors Affecting Sighting 46 CHAPTER 6 – MISCELLANEOUS 18 The Effect of Ground on Fire Effect 48 19 Observation of Fire 51 20 Elementary Theory of LMG 52 ANNEX Annex A Trajectory Table 55 FIGURES Figure 1 Hand Arm Characteristics 3 2 Military Rifle Characteristics 4 3 Sub Machine-Gun Characteristics 4 4 Light Machine-Gun Characteristics 5 5 Heavy Machine-Gun Characteristics 6 6 Bullet Spun by Rifling 8 7 Relative Bore Diameter of Small Arms 9 8 Definitions 10 9 First Catch 12 10 Effect of Range on Dangerous Space 13 11 Height of the Weapon above the Ground Level 14 12 The Height of the Object Fired 14 13 The Flatness of the Trajectory 14  iii Figure Page 14 The Conformation of the Ground 14 15 Enfilade Fire 18 16 Plunging Fire 19 17 Grazing Fire 19 18 The Eight Operating Functions 24 19 Cartridge Magazine Cut-Away View 26 20 Cartridge Belt 26 21 Cartridge Clip 27 22 Straight Pull Bolt Lock 27 23 Cartridge Charger 29 24 Extractor Action 32 25 Firing Pin and Sear Fundamentals 34 26 Bolt action Cocking Elements 35 27 Browning Machine-Gun Firing Mechanism 36 28 Revolver Trigger and Hammer Mechanism at Rest 37 29 Revolver Trigger and Hammer Mechanism Cocked 37 Position 30 Cone of Fire Against a Steep Hillside 49 31 Cone of Fire Against Rising Ground 49 32 Cone of Fire on Level Ground 49 33 Cone of Fire on Reverse Slop 50 34 A Defiladed Zone 50 35 Permissible Error 51 36 Cone of Fire From the Bipod 52 37 Cone of Fire From the Tripod 53  iv Figure Page 38 Dangerous Space, Dangerous Zone and Beaten 54 Zone 39 Beaten Zone at 500 and 1000 Yards (457.2 and 54 914.4 metres)  1 INFANTRY TRAINING Volume I INFANTRY PLATOON WEAPONS Pamphlet No. 12 THEORY OF SMALL ARMS FIRE (All Arms) INTRODUCTION 1. This pamphlet is intended to provide useful information, for officers and junior leaders of all arms, on the theory of small arms fire. It does not, however, describe weapons in detail but instead lays down broad functions and principles which are common to most weapons. Information, of the type contained is necessary in order that new problems may be solved and new types of small arms understood by personnel without an undue waste of time and energy. 2. Theory of Advancement of Small Arms. The Advancement in small arms has always been triggered primarily by two major factors, which are as under:- a. Shift in choices and priority by various armies in selection of small arms. b. Development both in weaponry and ammunition through Research and Development activities or through discoveries in wars. The purpose of development has been:- (1) To reduce the weight of the soldier once he goes into the battle field. (2) To increase its effect, it is complimentary to first one. (3) Enhance the hit probability.  2 Scope 3. Chapter 1 deals briefly with the characteristics which differentiate various classes of weapons. 4. Chapter 2 deals in general with common terms which are defined and illustrated diagrammatically. 5. Operating functions, which are common to most weapons, are described in chapter 3 and these form a basis for the assimilation of working knowledge about the small arms. 6. Chapter 4 deals with the design features of small arms and their ammunition. Discussion of factors responsible for variations in the performance of a particular weapon will be found as a useful reference for study by unit instructors. 7. Sights, which have an important bearing on theory, are dealt with in chapter 5. 8. In chapter 6, effect of ground and observation on fire effect has been illustrated. Elementary theory of LMG, with particular stress on Cone of Fire, Dangerous Space, Dangerous Zone and Beaten Zone are also discussed in this part. 9. Detailed information, regarding assembling, disassembling, functioning and maintenance, peculiar to various weapons should be sought in the individual training pamphlets concerned. CHAPTER 1 CLASSIFICATION OF SMALL ARMS SECTION 1 – CLASSES BY USE Hand Arms 1. Hand arms are those weapons which are held in one hand for use or for firing. Typical examples of this type of weapon are the  3 revolver, pistol, knife and hand grenade. These weapons are also called side-arms because of the practice of securing them to the user's side. As side-arms are small, they are meant for short range and are generally used for defensive purposes only. For offensive action the soldier is provided with weapons of longer range and greater striking power. Night operations and other engagements requiring hand to hand fighting and silence to ensure surprise are usually undertaken with hand arms. 2. Figure 1 shows the characteristic features of a pre-preventative type of military hand arm. Figure 1 - Hand Arm Characteristics. Shoulder Arms 3. This class of weapons includes those which are braced against the shoulder when firing to absorb the shock of recoil and to increase the probability of hitting the target. This group includes rifles, sub machine-guns, light machine-guns and rocket launchers. Sub machine-guns may be fired either from the shoulder or while held in both hands and braced against the body. Aiming of light machine- guns, which are classified as "light" because they weigh less than  4 medium machine-guns, is facilitated by use of a bipod or muzzle rest which steadies the muzzle end of the gun while the firer, in a prone position, supports the breech end or stock with his shoulder. 4. This features which differentiate these various classes of weapons are shown in Figures 2, 3 and 4. Figure 2 – Military Rifle Characteristics. Figure 3 – Sub Machine-Gun Characteristics.  5 Figure 4 – Light Machine-Gun Characteristics. Machine-Guns 5. Machine-guns fire projectiles of approximately the same size and striking power as those of rifles. In the heavy machine-gun class, heavier missiles are projected. To maintain rapid and continuous fire, cartridges art generally fed to the gun from a belt rather than from clips or magazines. The upper limit of size between light machine- guns and medium machine-guns is determined administratively. Like many other definitions of this group, there is no hard and fast rule. Because of their weight and relatively high rate of fire, machine-guns are usually mounted on a tripod or other type of mount. The requirement for transporting the mount and the requisite supply of ammunition with the gun is solved by assigning several men, rather than an individual soldier to each machine-gun or by mounting it on aircrafts, tanks, boats or other vehicles. The mounts contain clamps, means of which the guns may be fixed in selected positions for use in indirect fire that is, fire which is directed by means of compass and clinometers setting or aiming lamp disc rather than by sights. MG1A3 when fired from a tripod is used in medium machine-gun role. The same weapon when fitted with the bipod and fired from the shoulder  6 is used as light machine-gun. General characteristics of this class of weapons are shown in Figure 5. Figure 5 – Medium Machine-Gun Characteristics. Other Types 6. There are several other groups of weapons that are not customarily included in the foregoing classification. These groups include such items like signal pistols fire signals and shot guns. SECTION 2 – CIASSES BY TYPES OF FUNCTIONING CYCLE Manual 1. A manually operated firearm is one in which the operations necessary to complete the action are performed by the firer. In most weapons of this class, there is some mechanical action to assist the gunner. For example, in rifle Number 4, the magazine spring feeds the  7 cartridges up into the path of the bolt so that they are in proper position for the bolt to push them into the chamber. The rifleman manipulates the bolt to complete various actions in the cycle of operation that is feeding, chambering, locking, unlocking, extracting and ejecting. In the revolver, the chamber with the new cartridge is rotated into alignment with the barrel by means of a mechanical linkage, yet the work is done by the firer and not by any automatic action of the revolver itself. Semi Automatic 2. A semi automatic fireman is the one in which the complete cycle of firing including cocking, extracting ejecting, reloading and locking is performed by power from cartridges without the effort of the firer except to squeeze or press the trigger. A gun action of this type reduces the firer's fatigue. The semi automatic feature prevents the firing of a continuous burst of fire with the consequent large consumption of ammunition. A semi automatic gun is a weapon in which the cycle is interrupted at the completion of each full cycle, just before firing, for example, rifle M1, rifle 7.62 mm and pistol 9 mm. Often automatic and semi automatic actions are combined to make the mechanism convertible to either type, at the will of the firer. Examples of this type are rifle G-3, LMG.303, SMG 7.62 mm and SMC 9 mm. Automatic 3. An automatic weapon is the one, which will continue to fire without interruption as long as a pressure is maintained on the trigger. The only action necessary to operate this type of weapon is to maintain a supply of cartridges in its magazine belt or feed way and to press the trigger whenever a burst of fire is desired. Automatic weapons include LMG 7.62 mm and MG1A3. Care should be exercised in the use of the term "automatic firearm" as it is commonly misapplied to weapons that are really semi automatic. Outstanding  8 examples of this usage are the so called automatic pistols and shot guns.  9 CHAPTER 2 DEFINITIONS SECTION 3 - DEFINITIONS RELATING TO WEAPONS Weapon 1. Any tool that can be used to apply or project lethal force. Actually, anything from a rolled up newspaper to a nuclear bomb can be considered as a weapon. The term "lethal weapon" is popular but is becoming redundant. Replica Firearm 2. Replica firearm means any device that is designed or intended to exactly resemble, or to resemble with near precision, a firearm, and that itself is not a firearm. Rifling 3. A barrel is said to be rifled when it has spiral grooves cut down the bore. There are “lands” between the grooves (See Figure 6). Figure 6 – Bullet Spun By Rifling. Calibre 4. Calibre is the (standard) diameter of the bore excluding the depth of the rifting grooves (See Figure 7).  10 Twist 5. Twist of rifling is the distance, measured in calibers, in which the grooves make one complete circuit of the bore. Axis of the Barrel 6. This is an imaginary line through the centre of the bore from breech to muzzle. Figure 7 – Relative Bore Diameter of Small Arms. Line of Sight 7. This is a straight line from the firer’s eye through the sights to the point of aim (See Figure 8).  11 AB. Axis of Barrel BG. Line of Departure LOC. Line of Sight BPS. Trajectory P. Culminating Point S. Point of Impact Figure 8 – Definitions. Line of Fire 8. This is the direction to the target from the muzzle of a weapon. Quadrant Elevation (QE) 9. Quadrant elevation is the angle which the axis of the bore makes with the horizon when the gun is laid before firing. Tangent Elevation (TE) 10. Tangent elevation is the angle (before firing) between the axis of the bore and the line of sight to the target. Jump 11. Jump is the angle in the vertical plane between the line of departure and the axis of the bore before firing. If the line of departure is above the axis of the bore, jump is a positive quantity; and if it is below the axis of the bore, jump is a negative quantity. Muzzle Velocity 12. It is the velocity with which a projectile leaves the muzzle of a weapon. Muzzle Brake 13. A device attached to the muzzle of a firearm which is designed to reduce the recoil of the firearm by redirecting the powder gases produced during firing. Many muzzle brakes also act as flash hiders.  12 Aperture Sight (Peep Sight) 14. A type of rear sight used on rifles and shot guns that features a thick rimmed aperture with a small opening mounted on the firearm's receiver. It is used with a flat topped blade front sight and provides a high degree of accuracy. However, it is difficult to use it in dim lighting conditions, specially if an extremely small opening "target" type aperture is used. Firearm 15. “Any instrument that projects a missile by gas pressure generated by the combustion of a propellant. Thus, air guns are not, by definition, firearms.” Or “Firearm means a barreled weapon from which any shot, bullet or other projectile can be discharged and that is capable of causing serious bodily injury or death to a person.” SECTION 4 – DEFINITIONS RELATING TO THE MOTION OF THE PROJECTILE THROUGH THE AIR Trajectory 1. The trajectory is the curved path taken by a bullet through its flight (See Figure 8). Line of Departure 2. The line of departure is the direction of motion of the projectile as it leaves the muzzle. It is tangent to the trajectory at the muzzle (See Figure 8). Vertex or Culminating Point 3. The vertex or culminating point is the highest point above the line of sight that a projectile reaches in its flight to the target. This point occurs at a little beyond half the distance which the bullet travels (See Figure 8).  13 Angle of Projection 4. Angle of projection for a given point on the trajectory is the vertical angle between the line of departure and the line of sight to that point. Angle of Descent 5. Angle of descent for a point on the trajectory is the angle between the line of arrival at that point and the line of sight to it. First Catch 6. This is the point where a projectile strikes the top of the target (See Figure 9). Figure 9 – First Catch. Point of Graze 7. The point of graze is the point at which the trajectory intersects the horizontal plane through the weapon. It is sometimes called the “ballistic point of graze” (See Figure 9). Dangerous Space 8. At a particulars range, this is the distance between the point of first catch and the first graze. Dangerous space depends upon the following factors:-  14 a. Range (See Figure 10). b. The height of the weapon above ground level (See Figure 11). c. The height of the object fired at (See Figure 12). d. The flatness of the trajectory of the weapons (See Figure 13). e. The conformation of the ground (See Figure 14). Figure 10 – Effect of Range on Dangerous Space.  15 Figure 11 – Height of Weapon above the Ground Level. Figure 12 – The Height of the Object Fired. Figure 13 – The Flatness of the Trajectory. D S R. Dangerous Space Rising Ground D S L. Dangerous Space Level Ground D S F. Dangerous Space Falling Ground Figure 14 – The Conformation of the Ground.  16 9. The dangerous space :- a. Decreases as the range increases, owing to steeper angle of descent of the bullet at the longer ranges (See Figure 10). b. Increases:- (1) The nearer the weapon is to the ground (See Figure 10). (2) The flatter the trajectory (See Figure 13). (3) The nearer the slope of the ground conforms to the angle of descent of the bullet (See Figure 14). Remaining Velocity 10. The remaining velocity is the velocity of the projectile at any projectile at any specified point on the trajectory. When it is not specified or implied by the context otherwise, it refers to the point of graze. Draft 11. It is the movement of a projectile in a lateral direction of right angle to its principal motion. It is caused by reaction between the air and the spinning projectile. It does not occur with finned projectiles. Stability 12. It is the tendency of a projectile to return to its level or balanced position. Without stability, a projectile would tumble over and over and have a very short range. Hang Fire 13. The discharge of a cartridge after an appreciable interval when its primer is struck by the firing pin. This condition can be caused by a deteriorated or defective primer or from a weak firing pin blow.  17 SECTION 5 – DEFINITIONS RELATING TO AUTOMATIC FIRE Automatic Firearm (Fully Automatic Firearm) 1. A firearm that may be discharged successively without interruption by a single actuation of its firing device until its ammunition supply is exhausted or it is deliberately stopped by its user. Generally referred to as a "machine-gun." Ammunition 2. The complete round or its components, including cartridge cases, primers, propellant powder, bullets or projectiles that are used in any firearm. Explosives 3. Any substance or article that is made, manufactured or used to produce an explosion, detonation, propulsive or pyrotechnic effect, except substances and articles that are not in and of themselves explosive. Bullet 4. The projectile(s) of bore diameter that comes out of the muzzle of a small arm. Chamber 5. That portion of a firearm in which the cartridge is placed for firing. In cannons, rifles, shot guns, single shot pistols and semi automatic pistols; it is the interior of the rearward portion of the barrel. In revolvers the chamber(s) are located in the revolving cylinder. Used as a verb (to chamber) it means to place a cartridge in a firearm's chamber in preparation for firing.  18 Dry Firing 6. The operation of a firearm without the use of ammunition, as a means of obtaining or retaining operational familiarity and technique. Dry firing must be done very carefully since the primary rule of firearm safety is that all firearms are always loaded. Semi Automatic Firearm (Self Loading Firearm) 7. A firearm that may not be discharged more than once at a single actuation of its firing device and that reloads automatically, from a self contained magazine, one round at a time, until its ammunition supply is exhausted. Burst of Fire 8. A number of rounds fired with one squeeze of the trigger of an automatic weapon is termed as a burst of fire. Cone of Fire 9. When a burst is fired, the bullets do not follow the same path. The vibration of the gun, variation in the ammunition and changing conditions of the barrel cause each trajectory to differ slightly from the other in a burst. The group of trajectories formed by a single burst is called the cone of fire Beaten Zone 10. The beaten zone is a long elliptical pattern formed by the inter- section of the cone of fire with the ground the pattern of the bullets is the thickest in the middle of the beaten zone. As the range increases, the length of the beaten zone decreases and the width increases. This is due to the increased angle of descent of the bullets. Beyond certain range, the beaten zone increases again especially laterally.  19 Dangerous Zone 11. It is the area of the beaten zone plus the dangerous space formed by the lowest bullets of the cone. Enfilade Fire 12. It is either frontal or flanking fire in which the long axis of the beaten zone coincides with the long axis of the target (See Figure 15). Notes: 1. From Position ‘A’ the Gun is Firing Frontally and thus Getting Few Kills with its Beaten Zone. 2. From Position ‘B’ the Gun is Firing on the Flank of Enemy Attacking Formation and thus its Beaten Zone Coincides with the Longer axis of the Enemy. Figure I5 – Enfilade Fire. Plunging Fire 13. It is fire in which the angle of fall of the bullets with reference to the slope of the ground is such that the dangerous space is practically confined to the beaten zone and the length of the beaten zone is materially shortened. Plunging fire is obtained when firing from high ground into low ground or firing into abruptly rising ground and also when firing at longer ranges (See Figure 16).  20 Notes:- a. From position 'A' the gun is firing from one raised ground to another, thus the beaten zone is restricted to one point. b. From position 'B' the gun is firing from a higher ground to lower ground, thus the beaten zone is restricted to one point. c. From position 'C' the gun is firing from a lower ground to higher ground, thus again the beaten zone is restricted to one point. d. In all three cases defiladed zone is created in which the enemy can be safe. Therefore the fire must be grazing or the trajectory conforming to the ground to achieve maximum effect of fire of automatic weapons. Figure 16 – Plunging Fire. Grazing Fire 14. It is the fire in which the centre of the cone of fire does not rise above the height of the standing man. An LMG/BAR fired over level or uniformly sloping ground can obtain grazing fire at ranges up to 500 metres (545 yards) (See Figure 17). Figure 17 – Grazing Fire.  21 SECTION 6 – DEFINITIONS CONCERNING ANTI-TANK WEAPONS AND PROJECTILES Rockets 1. Rockets are jet propelled weapons, consisting essentially of a warhead and a tube filled with propellant, with an opening at one end and a firm closing at the other. Stand off Distance 2. In order to get the maximum penetration effect from a projectile, based on hollow charge principle, it is necessary that the HE filling should detonate at a certain distance from the target. This distance between the HE filling and the target is known as stand off distance. This distance has been obtained by the give (hollow front portion) in all the short range anti-tank projectiles. Venturi 3. The constricted opening at on rear end of a rocket motor is known as venturi. It controls the flow of the gases from a rocket motor and it is so designed that the lateral expansion of the gases against the slopes of the nozzle gives the rocket a forward thrust. Bad Blast 4. In all the open breech anti-tank weapons when the propellant is ignited the gases and flames are blown backwards. This is known as back blast. Muzzle B1ast 5. Muzzle blast is the flame and unburnt particles of the propellant charge blown to the rear into the face of the firer after a rocket has left the launcher.  22 Ballistics 6. The study of moving projectiles. Internal ballistics deal with what happens inside of a firearm upon discharge. External ballistics is the study of a projectile's flight, and terminal ballistics is the study of the impact of a projectile. SECTION 7 – MISCELLANEOUS DEFINITIONS Ballistics 1. Ballistics, in its general sense, is the science of the motion of projectile. Internal Ballistics 2. Internal ballistics is the sequence of events which occurs between the moment the charge is ignited and the moment the projectile leaves the muzzle of the gun. External Ballistics 3. External ballistics is the sequence of events which occurs between the moment the projectile leaves the muzzle of the gun and the moment of impact or burst of the projectile. Inertia 4. It is the quality under which matter continues in its existing state of rest or uniform motion unless it is disturb by some external force. Derivatives of this basic quality are set back and rush forward forces which have been utilized in the making of modern anti-tank weapons.  23 Set Back Force 5. It is the force through which a body tends to fall back when set into sudden motion or accelerated. Falling back when a vehicle or the train moves forward is a common phenomenon. This force is utilized in arming the anti-tank projectiles. Push Forward Force 6. It is the opposite of set back force. Due to this force, a body tends to continue its motion when all of a sudden it is brought to a state of rest or it is retarded. When a vehicle stops suddenly the passengers are forced to lean forward. This is a common illustration of the same force. This force is utilized in detonating the fuze of modem anti-tank rockets and anti-tank grenades. Obturation 7. It is the locking or sealing of the breech of a weapon to prevent the leakage of gases when a cartridge is fired. Hang Fire 8. A hang fire occurs when the time interval between the releasing of the firing mechanism of a fire arm and the projectile from the chamber is longer than customary. It may be due to many causes, chief of which is faulty functioning of the primer or faulty ignition of the propellant. Cocking Oil 9. It is the self ignition of a cartridge inside an over heated chamber of a weapon.  24 Run Away Gun 10. When an automatic weapon keeps on firing against the wishes of the firer, it is termed as run away gun. CHAPTER 3 OPERATING FUNCTIONS SECTION 8 – GENERAL 1. The operations of loading, firing, and unloading a firearm are generally familiar to everyone. In a technical description of the operation of a weapon, however, it is necessary to divide the operations into elementary functions and to describe those parts of the gun which perform them. This section describes various methods which have been used to perform the individual functions. 2. It is first necessary to place a cartridge in the receiver, approximately in the back of the barrel. This function is called "Feeding." The action which moves the cartridge forward into the chamber of the gun barrel is called "Chambering." The operation of removing the cartridge or unloading the gun is divided into two parts "Extracting" or removing the cartridge or fired cartridge case from the chamber and "Ejecting" or removing the cartridge from the gun after it has been removed from the barrel. Blocking the barrel behind the cartridge and securing it so that the cartridge case will not be driven out by the high pressure or let the gases leak out and harm the firer is known as "Locking." Igniting the primer or actually firing the cartridge is called "Firing". Firing the cartridge requires the release of energy from within the gun to perform the step of unlocking or the of the breech end of the gun. Before firing another shot, it is necessary to return the firing mechanism to its original position. This action is known as "Cocking." (See Figure 18).  25 Figure 18 – The Eight Operating Functions. SECTION 9 – FEEDING 1. Feeding is the action of placing a cartridge in the receiver, approximately in the back of the barrel, ready for chambering. In its simplest form, it consists of moving a cartridge in the receiver by hand until it is approximately in back of the barrel. Some measure of complication is encountered if mouth of the magazine or feed way is not in alignment with the bore. This condition exists in shot guns which have the magaz1ne below the barrel and lifting mechanism to raise the cartridge to the axis of the barrel. A greater demand is placed upon the feeding device if the cartridge is to be withdrawn rear ward from a link or belt and then transferred to the bore axis. Machine- guns, such as the Browning type, use this action. In addition to the  26 movement of the entering cartridge, a belt-fed weapon is also required to advance the entire belt one step for each round In a magazine weapon, the magazine spring supplies this power, but in a belt-fed gun, power is taken from the force of the expanding powder gases. 2. Feeding mechanism may be simplified, if the cartridge is pushed directly forward from the link into the chamber. This type of action, with the exception of advancing the belt, approaches the simple construction of a magazine fed gun a type which was developed by the Germans and used in many of their machine-guns. 3. A magazine is a long, slender, spring-loaded container which holds the cartridges (See Figure 19). It can be inserted into the gun as a unit. Some magazines contain 3 single row of cartridges, others, a double (staggered) row. The cartridges are retained in the magazines between the magazine lips and the spring loaded follower. Being in the class of auxiliary or expendable equipment, magazines are usually made light and cheap and hence are readily damaged by rough handling. 4. Attempts have been made to relieve the dependence upon proper magazine lips by designing the mouth as a part of the weapon. For increased capacity, a drum magazine may be used. 5. To provide more rounds of continuous fire than are possible with separate box magazine, means have been devised to feed the gun with a long belt containing cartridges closely spaced. These belts are of many forms. They may be made of metal or woven fabric. If of the leather they are woven into a continuous series of pockets, as shown in Figure 20, from which the gun can extract each round in turn.  27 Figure 19 – Cartridge Magazine-Cut-Away View. 6. Metallic belts are articulated devices, which can be made to remain continuous after removal of the round as shown in Figure 20 or to "disintegrate" into individual links at that time. Belt can be classified in accordance with the way in which the cartridge is removed there from. The cartridge may be pushed directly from the belt into the chamber or may be withdrawn to the rear and then, by reverse movement, thrust into the chamber or stripped sideways from the link and then fed. Figure 20 – Cartridge Belt.  28 7. Small groups of cartridges may be loaded into a weapon by the use of a clip (See Figure 21) or a charger (See Figure 22). A clip holding 5 to 10 cartridges may be inserted into the magazine well behind the breech opening. This clip remains in the gun until all cartridges have been fed and fired, after which it is automatically ejected. Provision is usually made also for removing it from the gun at the will of the firer. A cartridge charger, sometimes also called a "clip". It is similar to the clip described above except that it usually holds only five or six rounds and is not placed in the gun with the cartridges. Instead, the charger remains out of the gun, the cartridges being stripped from it into a magazine space in the gun. Both chargers and clips are usually designed to be expendable and not reused. Figure 21 – Cartridge Clip. Figure 22 – Cartridge Charger.  29 SECTION 10 – CHAMBERING AND LOCKING Chambering 1. Chambering takes place when the bolt has stripped the new round from the feed mechanism and 1s moving it forward and the nose of the bullet contacts the bullet ramp at the rear of the barrel and guides the round into the chamber, The bolt closes on the bullet and the extractor snaps into the extracting groove around the base of the cartridge case. Locking 2. A locking device is necessary to prevent loss of gas pressure until after the bullet has left the muzzle of the barrel. The locking device, in addition to being sufficiently strong to perform this function, must also be quick and easy to operate. The complexity needed in the locking mechanism will, of course, depend on the strength of the forces developed by the cartridge which it secures. When comparing various types of gun locks, there are many features to be considered and balanced for operating efficiency and safety. However, in general, the shortest and simplest type of lock has been the most satisfactory. The type of lock employed will also be governed to a large extent by the source of power which is used to operate the weapon. 3. The bolt action type of lock is commonly used on hand- operated weapons and can also be fitted with a gas piston and actuated by gas pressure. This lock requires two distinct motions-one to move the breech block towards the barrel and obtained by engaging a lug on the head of the breech block ahead of corresponding locking surfaces on the barrel (See Figure 23). This type of lock can be used satisfactorily because it is possible to place the locking lugs near the front of the breech head, thus avoiding yielding under the firing pressure.  30 Figure 23 – Straight Pull Bolt Lock. 4. Many camming devices have been developed to permit a rotating bolt action, operated by a straight pull of the operating handle. SECTION 11 – FIRING AND UNLOCKING 1. Ignition of the primer is started when it is struck by the striker of a firing pin or hammer. The trip of the firing pin must be small in diameter so that it can strike the primer cup at the point where the primer anvil comes closest. It is believed that the primer is exploded by being compressed between these two metal surfaces. The blow struck must be delivered sharply or the entire primer assembly will be pressed into the cartridge case for it is held in position only by friction. Further, if struck slowly, the energy of the firing pin blow will be dissipated and the primer will not be ignited. 2. When the primer explodes, burning gases are blown at high pressure through the vent into the powder of the cartridge case, thereby igniting the main body of the propellant. These pressures tend to drive the primer cup out of the primer pocket in exactly the same fashion as the propellant drives the bullet out of the barrel. The primer cup is forced against the face of the breech closure. If the firing pin is too large in diameter, the breech closure will not be able to support the primer cup properly and the primer cup may be torn or ruptured, permitting gases to leak into the action of the gun. Leaking hot gases will eventually wear or erode the point of the firing pin and the firing pin itself in the bolt. As the passage becomes enlarged, it no longer  31 supports the firing pin directly in line with the primer anvil and the probability of misfire greatly increases. 3. The firing pin can take many forms. The falling hammer type employed in revolvers historically descended from the 'cock' or 'hammer' of the flintlock. It is generally used on low power weapons where the striker point of the hammer protrudes through a recoil plate of limited thickness which must support the chamber pressure. For reasons of strength, it is desirable to use long sliding pins which can be supported behind a greater thickness of metal. 4. Maximum thickness and strength are attained, of course, when the firing pin is an integral part of the breech block itself. In this type of action, the cartridge is moved forward into the chamber, being driven largely on the point of the firing pin. As the cartridge is light in weight, the firing pin does not indent the primer until the final moment of closing, when inertia of the breech drives the, striker point into the primer. This type of firing pin has been modified by supporting the firing pin upon a mechanical linkage which is activated at the last instant of closing the breech, thus driving the firing pin forward and causing it to protrude from the breech face. 5. For reasons of safety against accidental firing, it is preferred that the point of the firing pin be retracted behind the breech face except when it is deliberately moved forward to strike the primer. 6. A variation of the rotating hammer type may be used where the hammer, instead of striking directly on the primer, strikes on a long thin firing pin, permitting the use of a thick recoil plate. This design permits the driving spring and hammer release mechanism to be mounted in the receiver or frame of the gun and does not require it to be moved back and forthwith the operation of the gun action. If sufficient space is available in the moving parts of the breech block, the hammer may be dispensed with and the spring applied directly to the firing pin itself.  32 Unlocking 7. Unlocking occurs after the firing of the round. The breech block in the gun is rotated by a camming action provided by locking lugs on the breech block and the camming recesses in the receiver. Thus slow initial extraction is provided in weapons requiring this step. In recoil operated weapons, the recoiling parts move to the rear a slight distance in a locked position, before unlocking actually takes place. In sub machine-guns of the straight blow back type, there is no camming action; the cartridge is held in the chamber by weight of the bolt until pressure forces the bolt to the rear. SECTION 12 – EXTRACTING AND EJECTING 1. Proper extraction of the empty cartridge case from the chamber must be carefully timed. If the case is removed too soon after firing, the high powder pressure in the chamber will press the thin walls of the case against the walls of the barrel and an excessive effort will be required to extract it. This pressure will place heavy loads on the extractor. As there is usually not much room available to place the extractor in the mechanism, it is essential that the required dimensions be kept as small as possible. Early extraction is also undesirable because flash, smoke and carbon will be forced into the gun- mechanism, and in the face of the firer, if the case is removed while the pressure is still great. It is also possible that the case will be torn apart if the pressure holds it against the wall with excessive force. 2. On the other hand, extraction cannot be delayed unduly because the mechanism usually moves slowly until the cartridge case has been taken from the barrel and any loss of time at this phase of operation would seriously reduce the rate of fire of an automatic gun. 3. The extractor itself is a small hooked piece of metal either incorporated or supported by a spring which forces it into engagement  33 with the extracting rim of the cartridge case as shown in Figure 24. There is usually some small motion of the extractor as the case is thrown from it during the ejection operation. Figure 24 – Extractor Action. 4. Cases can also be removed from the chamber by rigidly fixed extractors. In the Browning Machine-Guns, this type takes the form of a 'T' slot. To insert the cartridge case into or remove it from the extractors of this type, it is necessary to rotate the case at right angles to the axis of the barrel. Ejecting 5. After being extracted from the chamber, the fired case must be ejected from the receiver of the gun. Ejection must take place in such a manner that the case will not fall back into the mechanism regardless of the attitude of the gun or the accelerations under which it is firing. The direction, in which the ejected case is thrown, should be planned in accordance with the use and installation of the weapon. In weapons such as rifles and pistols, it is desired, that the cases fly forward to the right so that they do not strike the firer. 6. If sufficient space exists to the rear of the weapon, it is possible to eject the case directly away from the breech, in the same direction as it was extracted. This may be accomplished by a push rod, as in revolvers, or by an air blast. In most cases, however, it is necessary to  34 eject the case through the top, bottom, or side of the receiver. If the case is withdrawn from the chamber by a single extractor holding it to the face of the breech block, it is possible to apply force at the other side of the cartridge case head or along its side which will spin it around the extractor and cause it to fly out of the gun. 7. The simplest method of performing this operation is to provide an obstruction on the inside wall of the receiver so that, as the breech block comes to the rear, the obstruction or ejector sliding in a groove in the breech block strikes the case as it is brought back. Proper location of the ejector along the side of the gun permits timing of the ejection action and throwing out of the case at the desired instant. A similar type of ejecting action may be obtained by making a spring loaded ejector into the face of the breech block. This type of ejector throws the case out of the gun as soon as the front of the case is freed from the chamber. As long as, the case is being extracted, the wall of the chamber holds it in position but afterwards, the ejector throws it out. SECTION 13 – COCKING 1. The energy which the firing pin or striker transmits to the primer is derived from the release of a spring, which must be compressed to fire the next round. This action is a part of the functioning required of an automatic weapon. Whether the firing pin is spring loaded or free and struck by spring driven hammer, it is customary to retract the firing pin behind the face of the breech block as soon as possible. This retraction prevents damaging or breaking of the firing pin if a cartridge case passes across it during feeding and also prevents accidental firing of a cartridge which might occur if the pin was protruding through the recoil plate. 2. Figure 25 shows the fundamentals of a firing pin and sear mechanism. The firing pin is contained in a breech block, which in this case, slides from left to right. The firing pin is forced to protrude from the breech block by spring pressure. As the breech block moves  35 towards the right, the sear and the compressed spring stop the firing pin, positioning it and the breech block in the relationship shown. The firing pin is released by drawing the sear downward. The tip of the firing pin will remain exposed until the breech block has completed its desired backward movement and has started to move forward again because the pin is stopped by the sear only on the forward motion. Figure 25 – Firing Pin and Sear Fundamentals. 3. The firing pin mechanism used in a bolt action rifle is somewhat similar to the one just described but includes an additional feature to retract the firing pin at the beginning of the bolt movement. Figure 26 shows that a cocking cam has been added to the rear of the bolt. In this action, the firing pin can slide but cannot rotate; consequently, when the bolt is rotated to open the gun action the cocking cam causes the firing pin to be retracted and the firing pin spring to be compressed. After the bolt has been rotated a sufficient angle, the stud on the firing pin rides completely off the inclined earn and rests on the square surface at the end of the bolt. It remains in this position until the bolt is again rotated at the conclusion of the closing  36 motion. When the bolt is finally closed, the firing pin (See Figure 26) catches on a sear and prevents the firing pin from going forward. Figure 26 – Bolt Action Cocking Elements. 4. In actions that do not use rotary bolt movement the sear may be enclosed in the breech block it self or may be attached to the receiver figure 27 shows the elements of the firing mechanism used in Browning machine-guns. All the breech block recoils to the left after firing, the top of the cocking lever, held in a cocking cam fixed in the receiver of the gun, causes the lower end of the cocking lever to move the firing pin under the sear, where it is held throughout the remainder of the recoil stroke and during the counter recoil stroke of the bolt. 5. Revolver mechanisms are entirely different from those described above. In a double action revolver, the mechanism can be cocked by pulling back or down on the hammer or by pulling the trigger. The method in which the trigger is pulled continuously to cock and fire the weapon. Is known as double action; if the mechanism can be cocked only by pulling back the hammer, it is known as "single action."  37 Figure 27 – Browning Machine-Gun Firing Mechanism. 6. The mechanism shown in figure 28 is at rest. The rear end of the trigger, when pressed or squeezed, engages under the lower end of the sear and raises sear carrying the hammer with it. At the end of the motion, the trigger slips from the sear and the hammer swings clockwise, the striker impinging on the primer of the cartridge. If the mechanism is cocked by drawing back on the hammer as shown in figure 29, the small nose on the point of the hammer, below the sear, will catch the trigger and raise the trigger as the hammer is moved. These parts are so shaped that, even though the hammer can raise the trigger, the mechanism will not return to its former position until the trigger is moved through its entire stroke. After the trigger is raised to the full extent permitted by the mechanism, the trigger will slip and engage the small notch at the lower right corner of the hammer. The position of this notch on the hammer is such that the trigger and the hammer are locked and the hammer cannot fa1l down.  38 Figure 28 – Revolver Trigger and Hammer Mechanism at Rest. Figure 29 – Revolver Trigger and Hammer Mechanism Cocked Position.  39 CHAPTER 4 DESIGN FEATURES OF SMALL ARMS AND THEIR AMMUNITION General In order to secure maximum accuracy from a weapon, it is essential that all its projectiles must leave the muzzle at the same velocity and should follow the same trajectory when fired at a certain angle of elevation. To meet this requirement, all cartridges must be uniform and the conditions of a weapon must remain the same from round to round. Experience shows that despite best efforts of the manufacturers, it is difficult to achieve 100% perfection in the weapons and their ammunition. In the succeeding sections, some of design features of weapons and ammunition have been discussed. SECTION 14 – INTERNAL BALLASTICS Sequence of Events When a Weapon is Fired 1. The Force of Explosion. When a round is fired, the propellant is ignited by the primer and thus gases are formed by the burning powder. Rate of burning is influenced by the surrounding pressure. Powder, ignited in open air, burns with a hot flame without any loud report or explosion. On the other hand, in a chamber where gases produced cannot escape and so cause a large pressure build-up, burning of powder is very rapid, taking place only in a few thousandth of a second. Under the pressure of the expanding gases, the bullet is driven out of the barrel with a tremendous force. 2. Effect of Rifling. When the propellant is ignited, within a very short period of time, the internal pressure is great enough to drive the bullet from the case, into the barrel. At the beginning of this motion, the bullet strikes the start of rifling. It cannot pass through the bore unless it is engraved and forced into the rifting. This force requires  40 some energy; so there is a slight delay in the motion of the bullet. As the powder burns, the pressure continues to rise. While the expanding gases are driving the bullet out, it is continuously guided by the lands and grooves. As a result of this, the bullet acquires a spinning motion by the time it comes out of the barrel. The more the pressure built-up in the chamber, and the rate of turn of the grooves, the greater will be the spin given to the bullet (See Figure 6). 3. Movement Due to Recoil. As the propellant charge burns inside the chamber, it is converted into gases which exert pressure with an equal force in all directions. Gases pressing against the walls of the chamber or barrel cannot produce any transverse movement. Pressure exerted towards the muzzle end drives the bullet out of the barrel. The same amount of pressure is exerted against the breech which results in the recoil. Recoil occurs when the bullet is being driven out by the expanding gases. If the breech block/bolt and barrel are rigidly fastened to the body of the weapon, it will recoil as a whole causing great force upon the shoulder of a firer. On the other hand if they are mounted loosely in the stock or receiver, they will move in relation to it thereby reducing the recoil. It may be mentioned that although the gas pressure acts only for a few thousandth of a second, it exerts several thousand pound pressure. The application of this large force tends to turn the weapon upwards and pivot it about the mount or the gunners shoulder. For example, the rifle will be more apt to remain pointed towards the target, if the stock is constructed more nearly in line with the barrel. However, due to the facts of human anatomy, raising the stock requires raising the sights a corresponding number of yards. The motion of a weapon in the vertical p1ane during the firing period is known as "Jump". As the weapon tends to move rearward due to recoil and jumps at the same instant that the bullet starts to move, it will have moved a slight distance before the bullet has left the muzzle. Any change in the direction of the gun barrel, between the time the trigger is moved and the instant the bullet leaves the barrel, will result in disturbing the aim and in changing direction in which the bullet is fired with resulting inaccuracy at the target.  41 Variations in the Performance of Weapon 4. Wet/Oily Barrel. If shots are fired with a wet or oily barrel, abnormal vibration and consequently erratic shooting will occur until the water or oil is burnt up. Bullets will normally strike high on the target when fired from a wet or oily barrel. 5. Wet/Oily Chamber or Cartridge. Should the chamber or the cartridge be oily or wet, extra back pressure will be developed on the bolt head/breech block or locking system, owing to lack of friction between the case and the chamber. This will affect vibration and erratic shooting will result. 6. Besting the Weapon. Resting a weapon at a wrong point may affect the jump, hence the shooting accuracy. The correct point is the point of balance in the case of rifles and bipod in the case of automatic weapons i.e. LMG et cetera. 7. Firing with a Bayonet or Launcher Fixed. This may affect the jump and consequently the shooting of a weapon. No two weapons shoot exactly alike when fired with a bayonet or launcher fixed. As a rough guide, it has been found that fixing the bayonet or launcher with Rifle Number 4 causes a drop in the position of the mean point of impact However, with M1 Rifle, the fixing of a bayonet does not cause any appreciable difference in the normal position of the mean point of impact. 8. Stocking up of the Weapon. It is the fitting of the fore end to the barrel and body. Any wearing of the fore end or loosening of screws or presence of and foreign body between the fore end and the barrel may cause the "Jump" and consequently the accuracy of a weapon. 9. Over Heated Chamber/Barrel. During continuous firing, tremendous amount of heat is generated inside the chamber and the barrel, as a result of which the barrel expands. Thus the bullets do not  42 get the desired frictional resistance; hence the desired velocity in an over heated barrel. 10. Heated up Ammunition. The temperature of the propellant charge before ignition has some effect on both the pressure and the velocity. A warm charge burns more quickly. 11. Wear and Tear of Chamber and Barrel. Due to chemical action of the hot propellant gasps and the mechanical abrasive action of the projectile, metal is gradually removed from the surface of the bore. This results in the enlargement of the bore which causes a gradual deterioration in the performance of a weapon. Wear and tear, near the commencement of rifting, causes decrease in muzzle velocity because the initial frictional resistance to the motion of the projectile decreases and the chamber capacity measures. Wear and tear taking place at the muzzle causes a general deterioration in consistency. 12. Variation in Ammunition. Normally ball tracer, armour piercing and incendiary rounds do not have the same muzzle velocity. This results in inconsistency in the performance of a weapon. In certain weapons where light and heavy bullets are used, it may be remembered that an increase in weight of the projectile causes a lower muzzle velocity. However, if shape, muzzle velocity and angle of the projectile are the same, the heavier bullet attains a longer range than the lighter one. For example, heavier bullet of HMG 7.62 mm having a muzzle velocity of 2770 feet per second can achieve a range of 5000 metres whereas the lighter bullet having a muzzle velocity of 2850 feet per second, when fired at the same elevation, goes only up to 3000 metres. SECTION 15 – AMMUNITION 1. Ammunition used in various closed breech small arms has the following components:-  43 a. The Cartridge Case. The case is of solid drawn brass with a groove or rim for extraction. It holds the entire assembly together i.e. the bullet at one end, the primer percussion cap at the base and the propellant charge inside the case. It is corrosion resistant thus moisture is not allowed to enter and desensitize the chemical elements contained. b. The Propellant Charge. The cartridge contains a smokeless powder in the form of small perforated grains or sticks i.e. nitrocellose or cordite sticks. When suitably ignited, it burns uniformly rapidly producing many times its own volume of gases at a high temperature and pressure. No outside agent such as oxygen is necessary for its burning. c. The Bullet. Normally the bullet is pointed and has a lead core inside a copper envelope. It is long in shape to have more ballistic co-efficient diameter of the bullet is slightly bigger than the calibre of the weapon from which it is fired for the following purposes:- (1) To allow the bullet to be engraved by the rifting of the barrel and thus cause a rotation to be given as it moves up the bore. (2) To prevent the escape of gases forward past the projectile. (3) To offer a certain initial resistance to movement which has the effect of ensuring regularity of ignition of the propellant charge and hence regularity in muzzle velocity. (4) To assist the projectile in its stabilization in the centre of the bore. d. Various types of bullets used in service are follows:- (1) Ball bullets with soft cores.  44 (2) Armour piercing bullets with hardened steel core. (3) Tracer bullets containing a compound usually similar to barium nitrate, in their rear portion. (4) Incendiary bullets containing phosphorus or other material in a steel container. CHAPTER 5 SIGHTS SECTION 16 – TYPES OF SIGHTS Open Sights 1. The most common form of sighting equipment on a weapon consists of two separate points which can be aligned with the target. This equipment normally consists of a front sight placed on the muzzle or foremost part of the weapon and a rear sight placed near the eye of the firer. Sights of this type are called open sights. For all weapons except those used for short ranges only, the near sight is made adjustable both in elevation and in deflection to compensate for the curved fight of the bullet between the weapon and the target. 2. The front sight is usually of simple construction, being a post or rod which can be seen sharply outlined against the target. It is customary to make the front sight with sharp comers so that it may show up clearly against nature objects. A hood or protector may be provided to prevent the front sight from accidental damage and to prevent a soldier from cutting himself in performing his duties. 3. Several types of rear sights are in existence. For short range firing, the rear sight does not need to be adjustable. Even in this type, it is customary to provide some means of initially adjusting the sight at the factory to compensate for manufacturing variations. For moderate ranges, a simple mechanism capable of being slid or moved  45 by thumb screws in two perpendicular directions is used. For longer ranges, the sight may be made foldable, so that the rear sight leaf may be laid down along the barrel when the gun is being transported rather than in an exposed position where it can be easily damaged. 4. The rear sight is provided with a hole or notch through which the front sight and target are viewed. The rear sight may be placed as close to the eye as practicable, in which case the eye will be automatically centred behind the aperture If the rear sight is to be placed a sufficient distance in front of the firer's eye, so that the sight may be clearly seen, then either the notch type or the aperture type may be used. 5. Several attempts have been made to provide luminous sights so that a firearm may be operated at dusk or in the dark. These sights have generally been unsatisfactory for several reasons. First, the target itself may be indistinct or invisible due to darkness; second, the luminosity level of illuminated sights has not been satisfactory to permit accurate aiming under these conditions. Extensive tests have been conducted on sight of this type, but none have been found sufficiently satisfactory for general adoption or continued use. 6. An immense amount of ingenuity has been expended on the design of various types of blade front sights and aperture rear sights. Each type has its proponents and may have some special advantages. At the present time, all military weapons of the world use sights of similar design. It may, therefore, be reasonably assumed that they represent the best all around compromise among the various types. 7. When firing against moving objects, particularly against rapidly moving aircraft, it is necessary to aim the gun in front of the target so that the bullets and the target will arrive at the same point at the same time. If the guns were aimed directly at the moving airplane, the projectiles would fall behind and below it. The distance which the gun must be aimed in front of the target is called "Lead" and may be as large as 1500 or 20. The exact amount of this lead will vary according  46 to several conditions such as range, angular elevation, course and speed of the target, and the exterior ballistic characteristics of the ammunition being fired. It is impossible to compute these conditions within small arms weapons. It is; therefore, necessary to use tracer ammunition and fire more than one small arms at a time so that the aircraft is made to pass through a net of fire. Optical Sights 8. Optical sights are provided to give the firer an enlarged view of his target. These sights are usually straight line telescopes which magnify the target approximately two to four times. Larger magnifications suffer from a lack of illumination and such enlargement of the image that any small motion of the weapon is magnified greatly, making it difficult to hold a steady aim. The field of view through a telescope decreases as the magnification increases so that large magnifying power also makes it difficult to locate and follow a target. Because of the expense of providing a satisfactory telescope which will be strong enough for use on a fireman, these sights are limited to weapons for special purposes only such as sniper rides. 9. A telescope consists usually of the following optical elements; objective, erecting system and eye lens (ocular) contained in a dust proof tube. These elements are supplemented by some, formal of reticle or scale within the telescope. This reticle, scale, or aiming post is seen by the gunner exactly as if it were on the target. By moving the aiming post or by selecting one of the various lines etched on the reticle, angular adjustment is made to compensate for range and deflection. Because of the sudden shock received by the firing of the gun, telescopes must be specially constructed for this use. 10. The objective lens forms an upside down image of the target. This image is located at the reticle. The erecting lens system turns this image right side up and this final image is enlarged by the lens.  47 11. The exposed optical elements of the telescope are delicate and should be given the utmost care and protection. Leather covers are sometimes provided to exclude dust and dirt and to cushion shocks and blows. They would be kept on the telescope whenever it is not in actual use. Particular attention should be given to the actual care of tile glass surfaces. Optical glass is a relatively soft material and is easily scratched and damaged when rubbed with common materials. Only lens paper provided for this purposes should be used. Some telescopic lenses are coated with a thin substance which increases the transmission of light through the lens. This substance can be seen when looking at the lens and appears to be a discoloured film. It has been applied there purposely, however, and must not be rubbed off. Telescopes 12. Telescopes M B4 and Number 32 are used for aiming the sniper's rifle. The telescopes are provided with elevation and windage adjustments operated by knobs. Turning of the knobs causes the reticle to move vertically and laterally. Movement of the reticle is signified by a click of the knob. A sliding sun shade is mountec1 on the objective end of the telescope and a soft rubber eye shield is attached to the eyepiece. The eyepiece can be focused by turning the focusing nut. Both instruments are operated in the same manner. They are of weather and fungus proof construction. SECTION 17 – FACTORS AFFECTING SIGHTING Elevation 1. In order to allow for the fall of the bullet, the line of departure must be directed as much above the object to be hit as the bullet would fall below it if the axis of the barrel were pointed at the target. This raising of the barrel to allow for the curve of the trajectory is termed "giving elevation."  48 2. As the target must be kept in view, a weapon is provided with sights, which enable the firer to adjust the elevation required without losing sight of his point of metal. Sighting of Small Arms Weapons 3. In sighting, an average elevation for each range has been adopted. This means that the sight graduations of each weapon give the average elevation required by many thousands of weapons. In addition each weapon is carefully tested at short range before issue and is sighted to hit within certain close limits of the point aimed at. There are, however, in each weapon small manufacturing variations which cannot be avoided in large-scale production. Further variations are produced by the wear of parts and by the slackening or tightening of screws. These inequalities produce individuality in each weapon which shows itself in a slight variation of the sighting elevation required. Everyone must, therefore, study the shooting peculiarities of the weapon with which he is armed. Sight Graduation 4. For ranges up to.545 yards (500 metres), each man should find out any error in sighting that may exist in his weapon and set his sights accordingly. At the longer ranges, the graduations on the back sight should be regarded as the best possible guide under all conditions. Wind 5. The effect of a side wind on the path of the bullet, is considerable at all ranges except the very shortest. Head and rear winds also have an effect on the bullet at longer ranges. When firing a MMG, for example, the following figures should be kept in mind:- a. For head or rear winds up to 1500 yards (1371.6 metres) no allowance necessary.  49 b. For a strong wind at 1500 yards (13-71.6 metres) deduct 50 yards (45.72 metres). Atmospheric Conditions 6. The effect of atmospheric conditions other than wind need not normally be considered. It is sufficient if it is realized that in fighting at high altitudes less elevation may be necessary. Alterations of temperature need not be taken into consideration, except that, when cartridges have become heated in the sun, rifles are liable to shoot high. 7. Wet ammunition and rain tend to make bullets go high and become scattered. Light 8. In bad light, the foresight is less distinctly seen than in a good light and more of it is unconsciously taka into the line of sight. This factor naturally affects the elevation used; 1ess being required on a dun than on a bright day. CHAPTER 6 MISCELLANCEOUS SECTION 18 – THE EFFECT OF GROUND ON FIRE EFFECT 1. Ground has an important bearing on fire effect. A study of the conformation of ground at the target 18, therefore, essential to obtain really accurate results. For example:- a. A cone of fire (See Figure 30) striking a steep hillside will cover a very small area of ground and. Therefore, produce a restricted beaten zone-AB.  50 Figure 30 – Cone of Fire on Level Ground. b. The same cone of fire (See Figure 31) striking a gentler slope will cover a slightly larger area of ground - BC. Figure 31 – Cone of Fire against Rising Ground. c. One level ground, the area covered will be still greater - DE (See Figure 32). Figure 32 – Cone of Fire on Level Ground. d. The greatest area swept by bullets will be where the fall of the ground conforms to the trajectory of the bullet; for example a reverse slope (See Figure 33), in which case  51 the Whole area FG is dangerous zone, of which FH is the beaten zone. Troops, even though undercover from view as at K would be in danger from fire from A. Figure 33 – Cone of Fire on Reverse Slope. 2. The above examples show that it is more difficult to obtain fire effect against rising ground than against ground which is flat or falling away. 3. A defiladed zone is the area of ground which would be included in the "beaten zone", but for the fact that a proportion of the bullets of the cone have met an obstruction, usually a piece of higher ground (See Figure 34). Figure 34 – A defiladed Zone.  52 SECTION 19 – OBSERVATION OF FIRE 1. Ranging is the process of detonating, by observation or fire. The direction and elevation required to hit a given target. 2. Observation is the beat method of obtaining correct sighting elevation, since the errors in judging distance, caused by variation in light ground et cetera are nullified. 3. The permissible error in ranging is the term applied to the error which can be made in estimating range, while still keeping the target within the beaten zone. The permissible error in ranging is equal to half the depth of the beaten zone for any particular range (See Figure 35). Figure 35 – Permissible Error.  53 For example, assume the target to be 500 yards (44K metres) distant. The beaten zone of the light machine-gun at that range is approximately 180 yards (164.61 metres) in depth. If the estimated range is accurate, hair the beaten zone will be in front and the other half beyond the target. If an error of over 90 yards (82.30 metres) is made, i.e. half the depth of the beaten zone at this range, the whole of the beaten zone will miss the target. SECTION 20 – ELEMENTARY THEORY OF LMG 1. When shots are fired from a LMG, the bullets pass through the air in the shape of a cone of fire, which is the pattern formed by a series of shots fired with the same elevation and point of aim. This pattern is oval in shape, its density decreasing from the centre outwards (See Figures 36 and 37). Figure 36 - Cone of Fire from the Bipod.  54 Figure 37 - Cone of Fire from the Bipod. 2. When automatic fire is correctly applied to a target, the bullets of the cone, on striking the ground, form a beaten zone round the target. The size of the beaten zone will vary with the range and slope of the ground in relation to the angle of descent of the bullets. 3. For fire to be effective, the target must be included in the dangerous zone, which is the area of the beaten zone PLUS the dangerous space funned by the lowest bullets of the cone (See Figure 38). 4. The pattern of the bullets is the thickest in the middle of beaten zone (See Figure 38). As the range increases, the depth of the beaten zone decreases (See Figure 39). This is due to increased angle of descent of the bullets. Beyond 1500 yards (1371.6 metres) the beaten zone increases again, especially, and at the same time the angle of descent becomes steeper and the dangerous space formed by the lowest bullets of the cone become less. As a result, more bullets have  55 to be fired to obtain fire effect at the longer ranges, and the range has to be more accurately known. Figure 38 – Dangerous Space, Dangerous Zone and Beaten Zone. Figure 39 – Beaten Zone at 500 and 1000 Yards (457.2 and 9144 metres).  56 Annex A TRAJECTORY TABLE Height of trajectory (in feet) above the line of sight of the zone 4 rifle, SMLE.303 inch, firing SAA,.303 inch, Mark 7, muzzle velocity 2,440 feet per second. Range 200 300 400 500 600 700 800 900 100 100 1200 in yards 300 0.7 400 1.6 1.4 500 2.6 2.9 2.0 600 3.7 4.4 4.1 2.6 700 4.9 6.2 6.6 5.8 3.6 800 6.3 8.3 9.4 9.4 7.9 1.8 900 7.9 10.7 12.6 13.3 12.6 10.3 6.2 1000 9.7 13.4 16.2 17.8 18.5 16.5 13.2 7.8 1100 11.7 16.5 20.3 22.9 24.1 23.7 21.3 17.3 10.5 1200 14.0 19.9 21.8 28.5 30.9 31.7 30.7 27.5 21.9 12.5