The first function of the breech-block is, as we have said, to act as a guide for the cartridge into the chamber ready for firing, after the fashion of the old Martini-Henry breech-block. The actual pushing forward of the cartridge is performed by a lever sliding on the top of the block. After the explosion a small vertical lever jerks out the cartridge-case against the block, and causes it to cannon downwards through the aperture in the trigger-plate already mentioned.
On the left-hand side of the breech casing is a small chamber, open at the top and on the side next the breech. To the top is clipped the magazine, filled with twenty-five cartridges. The magazine is shaped somewhat like a slice of melon, only that the curved back and front are parallel. The sides converge towards the inner edge. It is closed at the lower end by a spring secured by a catch. When a magazine is attached to the open top of the chamber the catch is released so as to put chamber and magazine in direct communication. The cartridges would then be able to drop straight into the breech chamber through the side slot, were the latter not protected by a curved horizontal shutter, called the distributer. Its action is such that when a cartridge is being passed through into the breech casing, the shutter closes, and holds the remaining cartridges in the magazine; and when the cartridge has passed it opens and lets the next into position in the side casing.
As soon as a cartridge enters the breech it is pushed forward into the chamber ready for firing by the feeder lever. The magazine and the holder are so arranged that when the last cartridge has passed from the magazine to the distributer, the motion of the moving parts of the gun is arrested till the magazine is removed, when the motion is resumed so far as to push the remaining cartridge into the chamber and bring the breech-block into the firing position. When another magazine has been fixed in the holder, firing can be resumed by pulling the trigger; but if another magazine is not fixed in the holder the last cartridge cannot be fired by pulling the trigger, and only by pulling a handle which will be presently described. This arrangement secures the continuance of the automatic firing being interrupted only by the very brief interval required for charging the apparatus.
The gun is fired, as usual, by pulling a trigger. If a steady pull be kept on the trigger the whole contents of the magazine will be fired automatically (the last cartridge excepted); but if such continuous firing is not desired, a few shots at a time may be fired automatically by alternately pulling and releasing the trigger. If it is desired to fire shot by shot from the magazine, a small swivel on the trigger-guard is moved so as to limit the movement of the trigger. By moving this swivel out of the way, automatic firing is resumed. The gun may also be fired without a magazine by simply feeding cartridges by hand into the magazine holder. In front of the trigger-guard is a safety catch, and if this is set to "safe" the gun cannot be fired until the catch is moved to "fire."
It is obvious that the recoil cannot come into action until a shot has been fired. A handle is therefore provided on the right-hand side outside the casing, by means of which the bolt forming the axis of the recoil and percussion arms may be turned so as to imitate the action of the recoil. This handle must be turned to bring the first cartridge into the chamber, but this having been done, the handle returns to its normal position, and need not be moved again.
We may now watch a gunner at work. He chooses his position, opens out the supports, and pushes them into the ground so as to give the muzzle end a firm bearing. He then takes a magazine from the box he carries with him, and fixes it by a rapid motion into the magazine holder, then, resting his left hand on the stock to steady it, he pulls over the handle with his right so as to bring the barrel and all the moving mechanism into the backward position. He then releases the handle, and the recoil spring comes into action and drives the breech forward, when the controlling gear brings the front end of the breech-block into its downward position, admits the first cartridge into the breech and pushes it forward by the cartridge-feeder into the barrel chamber. The breech-block then rises to its central position at the back of the cartridge, and the gun is ready for firing.
If automatic firing is required, the gunner sets the swivel at the back of the trigger in the right position, sights the object at which he has to fire, and pulls the trigger, thereby exploding the first cartridge. The recoil then drives back the barrel and the breech. The breech-block is moved into its highest position, making room for the ejection of the empty cartridge-case, which is then ejected by the extractor. At the end of the recoil the block falls into its lowest position, the cartridge-feeder having then arrived at the back of the breech-block. The recoil-spring now drives the breech forward, admits the new cartridge on to the breech-block and drives it forward by the feeder into the chamber. The breech-block rises to its position behind the cartridge and is locked in that position. The percussion arm is then released automatically, strikes the hammer, and fires the second cartridge, the cycle of operations repeating itself till the last cartridge but one has been fired, when the magazine is charged and the cycle of operations is again renewed and continued till the second set of cartridges has been fired. The operations follow one another with such rapidity that the twenty-five cartridges contained in the magazine can be fired in less than two seconds. At the same time, the rate of firing remains under the control of the gunner, who can interrupt it at any moment by simply releasing the trigger. He can also alter his aim at any time and keep it directed on a moving object and fire at any suitable moment.
THE "REXER" AUTOMATIC MACHINE GUN