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When the bolt handle, which is attached to the bolt (9), is pulled to the rear, the hammer (10) is forced to the rear against the action of the hammer and sear spring (n) until the sear (12) is engaged in the sear notch in the trigger (13). The rearward motion of the bolt compresses the recoil spring (15) which, when the bolt handle is released at the rear position goes forward and drives the next car- tridge into the chamber, while the hammer is held in the rear position by the sear and trigger ready for firing. The trigger is pulled and released for each shot, but extraction and ejection of the fired car- tridge case and the feeding of the new cartridge are automatic. When the trigger is pulled, the sear is released and allows the hammer to go forward and strike the firing pin which ignites the cartridge. When the cartridge is ignited a portion of the powder gases pass through the gas port (16) into the gas cylinder (17) which drives the gas piston to the rear. The gas piston is linked with the bolt mechan- ism through a slide which transmits the force of the gases to the bolt. This serves to unlock the bolt and drive it to the rear to extract and eject the empty case and to compress the action spring and cock the hammer for the next shot. The bolt body is forced to the rear by the slide which is attached to the gas piston, and also linked with the bolt head (18) through rotating cams which rotate the bolt head sufficiently to clear the bolt head locking lugs of the locking recesses in the receiver.

AUTOMATIC RIFLES AND LIGHT MACHINE-GUNS As has been stated in an earlier part of this article the devel- opment of new tactical methods and conditions in the World War soon produced a demand for a light machine-gun or auto- matic rifle which could keep up with, and participate in, an

FIG. 9. Browning Automatic Rifle.

infantry attack at every stage of its progress. Various types of weapons were adopted for this purpose and classified as light machine-guns or automatic rifles. There is no distinct separation of these types, the term " light machine-gun " being usually applied to machine-guns weighing 20 to 30 Ib. fired from a bipod and used for fairly sustained direct fire. Practically all types are air-cooled by means of a heavy barrel with annular rings or a radiator. The automatic rifle, while it is sometimes supplied with a bipod, may be fired from the hip or shoulder and

The rifle is light and portable, weighing only 15^ Ib. and being only an inch or two longer than the short military rifle. It can be handled by one man as a shoulder rifle. As it is heavier than the ordinary military rifle, the recoil is very slight, and a man can fire the gun continuously without distress.

By means of a change lever, the action of the gun is made either semi-automatic (the trigger being pulled for each shot), or automatic (being continuous as long as the trigger is kept pressed and cartridges are supplied).

As a semi-automatic rifle it is very effective. As the trigger pull is as light as that of an ordinary military rifle, it is possible with practice, to fire 100 shots a minute without unduly tiring the finger. Used in this manner every shot can be well directed, which makes the gun in some conditions as effective as the heavy machine-gun, with a considerable saving in the amount of ammunition expended.

The gun, firing automatically, has a rate of between 450 and 500 shots per minute. The speed can be regulated to a certain extent by adjustment of the gas regulator. The weapon can be used as freely when firing automatically as when firing single shots, the firer lying down, standing, or advancing at will.

When a magazine has been emptied it can be dropped out of the gun by pressing the magazine release in the trigger guard and a full magazine quickly pushed into place with one hand, so that very little time is lost in changing magazines. 2

The mechanism is very simple and also extremely durable. Tests have been made where over 50,000 rounds have been fired out of the same rifle without any of the parts showing distress.

The rifle is gas-operated. A portion of the powder gases, while under pressure, are trapped near the muzzle of the gun and are caused to act upon a gas piston. The pressure of the gases forces the piston and slide to the rear against the action of the recoil spring, until stopped by the buffer, when the recoil spring returns the mechanism to its forward position.

The receiver (21) in which the barrel is firmly screwed con- tains the principal mechanism of the gun. The bolt-supports (23), upon which the bolt slides, are riveted in position. The bolt guide (25) fits in a slot cut in the receiver wall and is held in position by the bolt guide spring. The change lever stop (26) projects from a hole in the receiver wall in the path of the change lever and must be depressed before the change lever can be moved to the safe position. The buffer tube (28) behind the receiver contains an arrangement of friction cones, cups and springs. On the left-hand side of the receiver

is'capable of delivering limited sustained fire. Its weight varies from 14 to 20 pounds. The German " 08/15 " and " 08/18 " and the Bergmann, Lewis and Benet-Mercie are generally spoken of as light machine-guns. The Browning, Chauchat, light Hotchkiss and Madsen are examples of automatic rifles.

The Browning Automatic Rifle (figs. 9 and 10) is the standard automatic rifle of the United States army. 1

1 Brought out in 1917, just after America entered the war, and available in small numbers by Feb. 1918, it was not employed in battle till Sept., Gen. Pershing having become so convinced of its superiority over all other types in use that he preferred not to expose it to capture and copying by the enemy till the American army had been supplied with it on a large scale and had reaped the fruits of its superiority in a great battle. In effect, none was used before his offensive battles of Sept. but 4,608 were in action between that date and the Armistice. (C. F. A.)

FIG. 10. Browning Automatic Rifle.

are grooves in which the operating handle (34) slides. The forward end of the gas cylinder tube (36) is rigidly connected with the barrel. The bolt (39) carries the extractor (40) which is held by the ex- tractor spring (41). The firing pin (42) fits in the bolt, and has a cam lug which engages with a corresponding cam surface on the bolt lock (43). The downward motion of the bolt lock forces the firing pin back and prevents it from touching the cap of the cartridge until the arm is ready to fire. The bolt lock and link (44) are pivoted to the rear end of the bolt. The link connects the bolt lock and the slide (45), which moves horizontally in grooves in the receiver, the gas piston (46) being permanently attached to it. The slide is slotted to permit the magazine to pass through it, and has a notch on its lower rear end to engage with the sear (47). The link pin (48) passes through the link, hammer (49), and slide, pinning the three parts

2 Magazines holding 20 cartridges are the standard size ; they are also made to hold 30 and 40 cartridges. They are themselves filled by a device which presses in the cartridges, five at a time, from the usual clips.