THE MODERN MILITARY RIFLE The modern rifle is so constructed as to constitute a complete offensive and defensive arm for one man, of such a size and weight that one man can carry it, together with its ammunition and accessories and the other essentials that a soldier is required to carry over the ground and for the distances he is expected to cover in war. The weight of the military rifles of most countries averages about 9 lb. without the bayonet which weighs about 14 oz. All modern military rifles are breech-loaders with "bolt" systems and have magazines carrying 5-10 rounds. In all cases, except in the rifles of Greece and Russia, the double pull trigger system is employed. In this system, the mechanism is so arranged that, after a long light pull of the trigger, a greater resistance is suddenly felt. From this point on a heavier pull is required until the firing pin is released and flies forward to fire the round. The light pull is called the "first," and the other the "second" pull.
Usually the barrels taper towards the muzzle, either evenly or in steps, these latter being thought to break up or damp down the vibrations of the barrel caused by the explosion and which affect the accuracy of the shooting. In length the barrels run from about 24-32 in., the bores vary between •256 and .315 in. and the weights between 2 lb. 3 oz. and 3 lb. 3 oz.
The function of the bolt is to support the cartridge in the chamber during the explosion and so seal the bore against the escape of gas. On the right of the bolt, and usually towards the rear end is the bolt lever for its manipulation. The bolt is of steel, hollowed out to contain a firing pin and a spring (main spring), with which to fire the round. Mounted on the bolt and projecting beyond it is the extractor, which grips either the rim or cannelure at the base of the cartridge, when the bolt is fully forward.
When the bolt is drawn to the rear, the cartridge case is re moved from the chamber and its ejection from the rifle takes place during this backward movement. When the bolt is fully back, a round is pushed by a spring from the magazine and so held that when the bolt is again pushed forward, it drives this round in front of it into the chamber. During this forward
motion of the bolt, the firing pin within it, coming in contact with a sear which is operated by the trigger, is arrested. The bolt continues to go forward, compressing the mainspring which actu ates the firing pin. The firing pin is then in the cocked position, and if the trigger be pulled the sear will disengage from the firing pin and the latter will fly forward to fire the round. Bolts are always designed with locking devices, so that when the bolt is fully forward it is firmly held to the breech, supporting the cart ridge and sealing the bore against the pressure of gas. These lock ing devices must be strong, as the gas pressure generated by the explosion in modern military rifles may reach as high as 20 tons to the square inch. In short, it may be said that the heart of the whole rifle lies in the bolt and its components. Though breech actions are all of the bolt principle, there are, nevertheless, wide and varied differences in such bolts. There are two main bolt systems namely "rotating" bolts, and "straight pull" bolts. Of these, the former are most common. Rotating bolts are those which, before they can be unlocked and drawn to the rear, must be rotated.