Machine gun manual

by H. Douglas

The barrel is coated with copper to protect it from rust; the gunmetal valve referred to above, which prevents the escape of water to the rear, is fitted just in front of the breech end, which is formed in the shape of a block; this block has two studs, one on each side, called the barrel trunnions, by means of which the barrel is attached to the side plates.

The side plates are each provided with a hole to receive the barrel trunnions, and in the case of the ·303-in. gun, with hooks for engaging the recesses on the top of the barrel block; also guides in which the flanges of the lock move, which are enlarged at the rear end to act as crank stops; in addition each has a bearing, through which the crank passes, thus connecting the latter with the barrel; these bearings move in slots in the breech casing. The left side plate is fitted with a connecting rod spring to hold the connecting rod upright when the lock is removed, and the right side plate is fitted with a side plate spring near the barrel, to keep the extractor in its highest position when the lock is home. The left side plate is prolonged to the front, and has a recess in which the bottom lever of the feed block engages.

The crank is fitted with a connecting rod, which is free to rotate on the crank pin, and, outside the breech casing on the right, with a handle which has a curved projecting arm, and on the left with a fusee, to which is attached a chain.

The connecting rod is attached to the crank by means of an axis pin, called the crank pin, and is arranged to take the lock by means of an interrupted screw, thereby connecting the crank and the lock. The connecting rod is divided into two parts, enabling its length to be increased by inserting washers of varying thicknesses. By this means it is ensured that a firm pressure is kept on the base of the cartridge at the moment of firing, thus preventing separations.

On the left of the breech casing there is a strong spiral spring, called the fusee spring, the rear end of which is connected by the fusee chain and fusee with the crank; the front end is attached to the breech casing by means of the fusee spring box and adjusting screw, which passes through the front end of the fusee spring box, and through the nut at the front end of the spring.

The lock is attached to the connecting rod by the screwed head, and when in the firing position closes the breech. In this position it is held by the side levers, the crank (which bears against stops on the side plates), and the connecting rod, the joint being slightly above the horizontal, to prevent the breech being opened at the moment of firing. The lock has a reciprocating motion communicated to it by the rotation of the crank, and is kept in position during its backward and forward movements by means of flanges working in guides on the side plates, and, when at the end of its backward travel and clear of the guides, by the gunmetal block underneath the cover.

The extractor is moved upwards by means of the side and extractor levers, and when in its highest position, is retained there by means of the side plate spring; this ensures the hole for the firing pin being opposite the centre of the base of the cartridge when the lock is home. The upward and downward movements of the extractor are regulated by guide ribs and stops; the upper stop forms part of the lock casing, and the lower one is removable.

The feed block, which fits under the cover into a recess cut in the breech casing, is provided with a slide to which are attached two pawls with springs, for the purpose of moving the cartridges from right to left; the slide has a transverse motion given to it by means of two levers which are fitted together; the top lever has a slot which engages a stud on the slide, and on the bottom lever is a stud which engages in a recess in the left side plate; by this means the slide is connected with the recoiling portion. The feed block has also two stationary pawls, which engage under the belt and prevent it slipping backwards during firing. To facilitate the entrance of the cartridges, the feed block is provided with a band roller, and in addition has steel guides fitted above and below in the cartridge way, which ensure the cartridges coming to the exact position where they can be gripped by the extractor; they are prevented from being pushed too far through to the left by means of the cartridge and bullet stops, which are inside the feed block.

The gun is supplied with cartridges from a belt which passes from right to left through the feed block. This belt is formed by two pieces of webbing connected together by eyelets and brass strips of two lengths, the projecting strips showing how far the cartridges should be inserted; the belt is made thick at the edge next the bullets by being folded over a piece of cord, so that the cartridges may be kept parallel in passing through the feed block, and lie evenly in the ammunition belt boxes.

(Flexible steel belts are now being used. These fold into their box in sections, and by withdrawing a pin the unexpended portion can be detached and packed away immediately. They appear to be giving considerable satisfaction, inasmuch as “belt troubles” are practically impossible.)