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arm; the sportsman seldom fires more than three or four shots in quick succession and is usually in a position to give the self-loading rifle the care which its more complicated mechanism requires.

The principal requirements in a semi-automatic rifle are that the rifle shall not weigh more than nine or ten pounds, and shall have a simple mechanism which will stand the shock of service ammunition and the wear and tear of campaigning. The weapon must be capable of being used either automatically or by hand as an ordinary rifle, and for the rest must possess all the qualities now demanded of a good bolt-action rifle. The automatic action, there- fore, is not considered a substitute for any of the qualities of the present shoulder-rifle. No semi-automatic weapon so far designed has fulfilled these conditions to such a degree that it has been adopted in place of the bolt-action rifle. The Mondragon, a Mexican invention, has, however, been used by the Mexican Government to some extent, and in a modified form. A modification of this weapon was also used by Germany in the war, notably for the armament of aeroplanes. Two French models, the St. tienne and the " Carabine Meunier," were brought out toward the close of the war, but not extensively used.

FIG. 5. Winchester Auto-Loading Rifle.

The U.S. Ordnance Department recently (1920) held competitive tests, and further developments and tests have been made.

The principal advantages expected from the semi-automatic rifles are : increased rapidity of fire, less physical labour on the part of the soldier, and better moral, due to the knowledge that he can devote all his attention to the enemy and shoot without exertion or haste when necessary. On the other hand, the desirability of the semi-automatic rifle is not universally conceded. Some authorities consider the rate of fire of the present rifle to be quite as high as is consistent with accurate shooting and lay stress on the difficulties of ammunition supply. 1

Semi-automatic Sporting Rifles. The Winchester auto-loading system for rifles (fig. 5) utilizes the inertia of a heavily weighted bolt working against the compression of a coiled spring in the fore end to delay the rearward motion of the bolt at the moment of firing until the bullet has left the barrel. After this inertia is overcome, there still remains enough force to the recoil to move the bolt to the rear, eject the empty cartridge case, cock the hammer against the com- pression of the hammer spring, and finish the compression of the bolt

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FIG. 6. Browning Auto-Loading Rifle.

spring. When this has been accomplished, the bolt moves forward actuated by the bolt spring and feeds another cartridge into the chamber. A pull of the trigger now fires another shot. This rifle is made in various calibres, the most powerful being -401 in. The 200- grain bullet in this size gives a muzzle- velocity of 2,132 f.s. and has a muzzle-energy of 2,020 foot pounds. The French Air Service used this type of rifle to a limited extent in the armament of aeroplanes.

The Browning auto-loading system (fig. 6), used by Remington (U.S.A.) and the Fabrique Nationale (Belgium), differs from the Winchester in that the barrel (i), breech bolt (2), and bolt carrier (3) are locked together at the moment of firing, these parts recoiling together against a powerful spring (7) in a casing surrounding the barrel and in which the barrel slides. The rearward motion pushes the hammer (4) backward, cocking the action and compressing the

1 The incorporation of the light machine-gun in the small fighting unit of infantry bears on this question. (C. F. A.)

action spring (5) through the link (6) and the recoil spring (7). A buffer spring (8) also serves to retard the recoiling parts. At the completion of the backward motion the bolt-carrier latch (9) springs into a notch (10), locking the bolt in its rearmost position. The barrel and bolt carrier now start forward actuated by the recoil spring around the barrel ; the bolt carrier after moving a short distance is held by the bolt-carrier latch; the barrel continues its forward movement, turning the bolt by means of a helical cam slot in its side and un- locking it. The empty cartridge case is held until the forward motion of the barrel withdraws it from the chamber, after which it is ejected. When the barrel has reached its forward position, the barrel exten- sion (n) has forced the barrel lock down. This reacts against the bolt-carrier latch and allows the bolt carrier to be pushed forward by the action spring (5), carrying a fresh cartridge from the magazine (12) into the chamber and rotating the bolt so that the locking lugs are forced into their seats in the barrel extension, thus locking the bolt to the barrel.

FIG. 7. Mondragon Semi-Auto Rifle.

This rifle is made in -25-in., -3O-in., -32-in., and -35-in. calibres. In the last-named the 2Oo-grain bullet has a muzzle-velocity of 2,020 f.s. and an energy of 1,776 Ib. The magazine is loaded with a clip of five cartridges similar to military rifles. Owing to the locked bolt and recoiling barrel, high pressures can be used in this arm. The cartridge is reduced in diameter or necked down for the bullet. The mechanism is, however, much more complicated than in a rifle where the breech only is blown back.

Semi-automatic Military Rifles. The Mondragon semi-automatic military rifle (fig. 7) is the invention of Gen. Mondragon of the Mexican army. It was invented about 1891 and developed to its present state by Germany about 1915. The rifle is gas-operated, the gas being taken from a port in the barrel. It weighs about nine pounds, has the general appearance of the ordinary service rifle, is fitted for a bayonet, and is made in 7-mm. calibre. The characteristic feature of this rifle is the bolt mechanism, which permits the rifle to be used either as an auto-loading weapon or as a hand-operated shoulder rifle. The bolt (i) has three locking lugs on the forward end of the bolt and four on the rear end of the bolt, which are locked into locking recesses of the receiver (2). The bolt is made to rotate by two helical cam slots (3) in the side; two cam lugs, which are carried by the bolt handle, work these slots. The bolt handle is connected with the gas piston so that when the powder gases enter the gas chamber and drive the pisjon to the rear, the bolt handle is carried with it and causes the bolt to rotate and unlock, and move to the rear, extracts the empty case and compresses the recoil spring (4) which is coiled round the gas cylinder, and drives the mechanism forward after it has been arrested in the rear by the buffer spring. A gas adjustment is provided to regulate the amount of gas delivered to the gas cylin- der, so that the rate of working can be to some extent regulated. The magazine has a capacity of 10 rounds. Another form of maga- zine, for aircraft purposes, is of the Luger "snail," or barrel type (see PISTOL), and holds 30 rounds. The rifle is provided with a sep- arate hammer (5) which is linked up with the trigger mechanism as

FIG. 8. St. tienne Semi-Auto Rifle.

shown in the section. The change to hand-loading is done by means of a releasing catch on the bolt handle which disconnects this from the gas piston. The gas port in the barrel may also be closed by means of a valve. A safety device (6) is provided which disconnects the trigger if carried in a safe position.

The German pattern was officially known as the Aviator's Auto- matic Carbine (Flieger-Selbstlader Karabiner), model 1915, and was chiefly and successfully used for the purpose indicated by its name. It was also for a time tried as an artillery carbine, but for this pur- pose it proved unsuitable, in that it failed to stand the rough usage and careless handling of field warfare.

The St. fctienne Semi-automatic Rifle (a French " semi-automatic rifle, model 1918 ") is a gas-operated semi-automatic rifle which weighs about n| Ib., is about 52 in. long, and has an ordinary rifle sight and bayonet fitting (fij*.8). It takes the French Lebel 8-mm. cartridge. The magazine which has a capacity of five cartridges is charged through the bottom of the magazine housing (8), which is hinged.