Page:EB1911 - Volume 17.djvu/259

 piston when it has been driven back by the gases. As already stated, a lug on the under surface just in rear of the cam (f) engages with the front of the mainspring.

Taking first the position shown in fig. 15 with the breech closed and locked and the cartridge fired, it will be seen that the breech is locked by the upper cam (f′), on the end of the piston, F, having caused the movable locking-dog (h) to fall and bear against the recoil blocks Z (see fig. 14 also) on the walls of the receiver or frame B. Consequently the breech is not unlocked until the piston has moved sufficiently to the rear for the lower cam (f′) to lift the locking-dog (h) clear of the recoil blocks Z. As the piston F is not actuated by the gases until the bullet has passed the port (c), and then has to move a short distance before the locking-dog is raised, the bullet is clear of the muzzle before the breech is unlocked.

As the piston continues to recoil it draws back the striker J and then the breech-block H, and is then caught and retained by the engagement of the sear (f) with the trigger N, and the position assumed is that shown in fig. 14.

From the head or nose-piece I of the breech-block projects the claw K of a spring extractor which, as the cartridge is pushed home by the breech-block, seizes it, extracting the fired case when the breech-block is withdrawn. Ejection of the fired case is effected by means of the ejector L (fig. 16) which catches against the base of the case, on the opposite side to the extractor claw, and so throws it sideways through the oblong-pointed opening in the receiver just in rear of the breech (see fig. 14).

The platform on the top of the feed-box through which the teeth of the smaller feed-wheel U project, and on which the feed-strips rest, lies below the axial line of the breech-block H, so that the face or nose-piece I of the latter only engages a portion of the base of the cartridge in the feed-strip as it pushes the cartridge into the breech, the bullet of the cartridge being guided into the breech by the incline at the opening of the latter. This point should be specially noted, the object of the arrangement being to enable the under surface of the breech-block to clear the clips which hold the cartridges in the feed-strips. The cartridge therefore, being extracted in the line of the axis of the block, is ejected through an opening above its plane of entry in the feed-strip.

Returning to the position shown in fig. 16, if the trigger be pulled, the compressed spring M reacts and drives the piston forwards, carrying the breech-block with it, the latter in turn driving a cartridge in front of it out of the feed-strip. When the block and cartridge are home, and not till then, the piston completes its travel, the upper cam (f′) locking the dog (h), and the firing-pin protrudes and fires the cartridge. Anything, therefore, which prevents the breech-block from being home against the breech, or the locking-dog from falling in front of the recoil blocks Z, renders firing of the cartridge impossible. Clearly if the trigger be kept depressed the action becomes automatic.

A special feature of this gun is the absence of a separate spring to actuate the firing-pin; the recoil spring M performing this function, in addition to that of driving the piston forwards.

The feed-strips have holes in them in which the teeth of the smaller feed-wheel U engage. The engagement of this feed with the piston F can be released by pulling out the feed arbor W, so that the strips can be removed at any time.

When the last shot in a feed-strip has been fired a stop (V) holds the piston and block ready for a fresh feed-strip to be inserted. As the stop V acts quite independently of the trigger, this action takes place even if the trigger be still depressed after the last cartridge in a strip has been fired.

To cock the gun, when in the locked position, a cocking handle G is provided. This has a long arm projecting to the front with a catch which takes against the front of the lug on the under side of the piston. To prepare the gun for action the gun is cocked, and a feed-strip is pushed into the feed-block.

The pressure of the gas on the piston is regulated by the regulator screw D, by means of which the space in the cylinder C in front of the piston F can be reduced or increased.

A safety lock R is furnished, which is a “half round” pin which can be turned so as to enter the semicircular slot just in front of the sear (f), and so hold back the piston when in the cocked position.

Radiation of the heat, generated in the barrel by rapid fire, is facilitated by the radiator (a), which consists of rings on the barrel close to the breech, which offer an increased surface to the air.

The gun is sighted to 2000 yds., with the ordinary flap back-sight, weighs about 53 ℔, and can fire from 500 to 600 rounds per minute.

[The diagrams have been made from drawings, by permission of the Hotchkiss Ordnance Company.]

The Colt automatic gun, which has been adopted by the American army and navy, and was used by the British in S. Africa, depends for its action, similarly to the Hotchkiss, on the escape of a small portion of the gases of explosion through a

port in the barrel a short distance from the muzzle. Figs. 17 and 18 give a plan, and side elevation with the left side plate removed, respectively. Into the recess in the barrel (92) just below the port fits the piston (35), capable of slight motion round the pivot (36), by which it is attached to the gas lever (29). The latter is a bell-crank lever pivoted at (34), its short arm being attached