Recoil and Gas.—In the Vickers gun (see fig. 5) gas is trapped at the muzzle and rebounds on to a muzzled cup screwed to the barrel, thus augmenting the recoil. For about -k in. of recoil the barrel and lock are held together in the locked position, By this time the bullet is clear of the barrel and the unlocking begins. Attached to trunnions on the barrel are side-plates which move with it. Over the breech is the feed block into which the cartridge belt is fed by a slide similar to that used in the Browning, but operated by a lever in the left side-plate. Further to the rear and between the side-plates is the crank with the connecting rod to which the lock is attached. The crank is prolonged outside to the right of the gun and on it is mounted a crank-handle. This latter is so shaped that on coming into contact with a "roller" during the recoil it is rotated upwards and to the rear. This causes similar movement of the crank and by this means the lock is withdrawn from the breech. A strong spring on the left of the gun called a fuzee spring is put into tension by the rotating of a fuzee to which the spring is attached at the left hand of the crank. The barrel and side-plates are returned to their forward position by a secondary movement due to the crank-handle and roller, but the lock is brought forward by the rotating action given to the crank by the fuzee spring. On the face of the lock is the extractor. When the lock goes to the rear the extractor drops, but rises again to its full height when the lock is fully forward. During rapid fire when the extractor is up it is grip ping a live round in the feed-block, and supporting the round in the chamber. When the lock travels to the rear the extractor drops, and the spent round is extracted and ejected through the bottom of the gun, and the live round is brought to the same level as the chamber. As the lock goes forward the live round is placed in the chamber and the extractor completes the cycle by rising again to grip another live round in the feed-block. The firing pin and spring, sear and trigger, etc., are contained within the lock. A firing lever operates the trigger and so long as this firing lever is pressed, this cycle of operations will continue as described.
Cartridge Projection.—The Austrian Schwarzlose (see fig. 6) is inertia operated, i.e., the backward thrust of the cartridge drives to the rear a heavy breech-block against a strong spring, which in turn pushes it forward. To ensure against the cartridge gripping the chamber too tightly and so having insufficient thrust, provision is made to oil each cartridge before its insertion into the chamber. The cartridge belt is led from the right on a toothed wheel situated below and in the rear of the barrel. This wheel is rotated by the movements of the breech-block. A claw at the bottom of the breech-block draws a cartridge from the belt on to the rotating wheel and this places the round in front of the breech-block to be driven forward into the chamber. A heavy firing pin passes through the breech-block and is pressed for ward by the mainspring. An arm is connected to the firing pin and it has on it a bent or step which engages on a similar bent on the breech-block when the firing pin is cocked. A trigger bar
when drawn to the rear by a thumb piece at the end of the gun raises this arm and when the bents are disengaged the firing pin flies forward to fire the round. Ejection is to the left and is effected by a plunger on the right side of the breech-block.
Recoil and Cartridge Pro jection.—The Italian Revelli uses a combination of barrel re coil and cartridge projection. A sleeve is attached at the rear of the barrel. Inside this sleeve lies the breech-block and inside the latter is the firing pin and main spring. This spring drives the breech-block and the firing pin forward. On firing, barrel, sleeve and breech-block move together to the rear a distance of 4 mm., after which the breech-block goes on free for about 6 in., compressing the mainspring. The locked motion of these princi pal components is explained above under "Locking Actions." A sear which engages with the firing pin is operated by a thumb piece plunger at the rear of the gun, which, when pressed, dis engages the sear and firing pin, A secondary sear is also provided which prevents the gun from being fired if the moving parts are not fully forward and the gun is thus mechanically safe.
This is the only well-known water-cooled machine gun which is not belt fed. The cartridges are contained in a magazine holding so rounds, there being ten compartments, each with platform and spring, The breech-block on going forward takes the top round from the first compartment and when this is emptied the maga zine is caused to move to the right so bringing the next compart ment into action and so on until the fiftieth round is fired, when the magazine is knocked clear of the gun. A secondary mechanical safety device consists of a small plunger protruding into the in side of the breech-block. The firing pin on going forward meets this and drives it out and towards the left. A recess is made in the body casing so positioned as to take this plunger when the breech-block is fully forward. If the latter is not fully forward, the plunger cannot move into the recess and its tail prevents the firing pin from protruding.
From the soldier's or hunter's point of view there exist certain features of small arms and their ammunition upon which it would be desirable to improve. To both the requirement of see ing without being seen is ever present. The flash of the explosion is, however, unmistakable, especially at night, and at once dis closes the presence and the position of the firer. Possibly in the future a special powder or other means will be devised which will reduce or even eliminate the flash of the discharge. Such powders have been produced in the United States. Silence, too, especially if coupled with a flashless discharge, would increase the prob ability of the firer remaining undetected. In the past, attempts have been made to reduce the noise of the explosion by means of a silencer, but apparently they have not met with such success as to have merited adoption.