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loses its velocity very rapidly, which renders it less suitable than a heavier bullet for employment in machine-gun work, where effectiveness at long range is required. So long, therefore, as the ammunition of rifles and machine-guns remains interchange- able it is probable that no further reductions of calibre and bullet weight will take place. At the same time, the develop- ment of the heavy machine-gun itself may quite possibly call for not merely the retention of the present common calibre but an actual increase of calibre beyond what is admissible for the rifle. The principle of interchangeable ammunition has recently been questioned by some experts who would prefer that each class of weapon should be free to develop along its own lines; and already experiments have been carried out in the United States, not indeed with two calibre, but with two bullet weights, a bullet of 180 grains being designed for the machine-gun (and for occasional use for special purposes in the rifle) while the old bullet of 1 50 grains is retained for the shoulder weapon.

The only new model service bolt-action rifle produced by belligerents during the war on a large scale was the British rifle, 303, pattern 1914, which was later adapted to -30 U.S. ammuni- tion and manufactured for the United States; about 2,500,00x5 rifles of this type being produced in that country during the eighteen months preceding the Armistice.

British Riflss of the War Period. Before the war, the British service rifle, the short Lee-Enfield of -303-^. calibre, had been subjected to a good deal of criticism, and the War Office, after much experimenting with various types of cartridges, found that it was not possible to obtain as high a velocity with this rifle as was desired. An improvement was effected, however, in the adoption of the Mark VII. ammunition, the pointed bullet of which weighs 174 grains instead of 215 grains as in the Mark VI., the muzzle velocity being 2,440 f.s., with a chamber pressure of 45,000 Ib. This ammunition, however, did not give the ballistic qualities desired and the design of a new rifle was taken up. A rifle was finally evolved with a bore -276 in. in diameter, and chambered for a rimless cartridge, giving a muzzle velocity of about 2,800 f.s., and a chamber pressure of 51,000 Ib., and it is probable that this model would have been further perfected and adopted but for the beginning of the war. Military con- siderations then prevented its adoption in its original form, and it was modified to take the existing Mark VII. -303 ammunition, and manufactured in the United States as the " British Rifle, Pattern 1914." The short magazine Lee-Enfield with Mark VII. ammunition, however, remained the standard British arm throughout the war; though the new rifle was also used.

Upon the entrance of the United States into the conflict, as a number of American factories were equipped to manufacture this rifle, it was again modified to accommodate the U.S. service ammunition and used as a substitute for the calibre -30, model of 1903 (Springfield), under the name of the " U.S. Rifle Model of 1917." As chambered and bored for the U.S. ammunition, the rifle had approximately the same ballistic qualities as the Springfield. The British and American models of this rifle are the same in their essential features, except that the latter has not the long-range (dial and aperture) sights of British rifles. A remarkable feature common to both rifles is the position of the rear sight between two protecting lugs on the bridge of the receiver. This position of the rear sight gives a distance from back sight and fore sight of 31-76 in., that is, almost exactly over the trigger instead of in the customary position, a hand's breadth or more in front of the magazine. Further details will be found in the article SIGHTS. The length of the rifle overall is 46-3 inches. The weight without bayonet is 9 Ib., 3 oz.; the sword bayonet is about 22 in. long (blade 17 in.) and weighs 15 oz. The magazine holds five cartridges which are loaded from a clip. The bore has five grooves, left-hand uniform twist, one turn in 10 inches.

The action of this rifle is as follows (figs. I and 2). The cycle of operations is assumed to start with the extraction of a' fired cartridge case. The bolt handle is raised and the cocking piece forced to the rear in the bolt by the half-cocking cam. This also withdraws the striker into the bolt. When the locking lugs on the bolt are clear the extracting cams on the bolt and receiver engage and the continued

rotation of the bolt retracts the latter and loosens and partly with- draws the cartridge case (primary extraction), the extractor and sleeve being prevented from turning by the receiver. When the limit of the turning movement in the bolt is reached, it is drawn to the rear, withdrawing the empty cartridge case; during this movement the cocking piece rides over the sear nose and depresses it ; the safety stud rises in the clearance cut in the bolt. When the cocking piece clears the sear nose, the sear spring returns the sear to normal posi- tion. The slotted locking lug (left hand) of the bolt now reaches the ejector, the latter protruding in the slot sufficiently to strike the rear of the empty case and eject it to the right. After a further slight backward movement the bolt lug comes in contact with the bolt stop, preventing further movement. If the magazine is now empty the follower rises and its rib prevents the closing of the bolt. If not, the magazine spring has pushed another cartridge up and into the path of the bolt, the forward movement of which forces it forward and up over the cartridge ramp.

During the early part of the closing movement of the bolt, the ejector is pushed outward by the bolt. Later, the sear notch in the cocking piece engages the sear nose, and is arrested. The bolt then slides forward over the striker, further compressing the main spring.

When the rotation of the bolt by the handle begins, the locking lugs engage the locking cams, and force the bolt home, seating the cartridge, and further compressing the main spring. The rotation of the bolt restores the half cocking cam, so that it is out of the path of fall of the cocking-piece lug.

The bolt is now locked, the mainspring is fully compressed, and the cocking piece is held by the sear nose.

When the trigger is squeezed, the bearing of the trigger first acts on the bearing of the receiver, slowly depressing the sear nose. Then the heel of the trigger engages the receiver, and completes the de- pression of the sear nose, which ends in the release of the cocking piece by the sear nose. The striker is then acted upon by the main- spring, and, striking the primer of the cartridge, detonates the same.

FIGS, 1 and 2. British Rifle (Pattern '14) U.S. Model of 1917.

During the depression of the sear nose, the safety stud rises through the hole in the bottom of the well and enters the interlock slot in the bolt. If the bolt is not fully locked, the interlock slot will not register with the safety stud, and the trigger cannot be pulled.

United States. When the United States entered the war its standard rifle was the " U.S. Rifle, Model of 1903 " (Spring- field). There were only about 600,000 of these on hand, and very limited possibilities of immediate expansion. To obviate delay, therefore, it was decided, as above mentioned, to adopt the British Pattern '14 rifle which had been manufactured in the United States in large quantities. This rifle, modified as pre- viously noted, was used very successfully by a large portion of the U.S. troops; only the regular army and part of the National Guard continuing to use the Springfield. The Springfield, how- ever, is still (1921) the official arm, the 1917 rifles having been withdrawn after the Armistice.

Other Nations. The Lebel magazine rifle, calibre 8 mm., model of 1886-93, is still the standard arm of the French infantry. The magazine is tubular, lies under the barrel, and holds eight cartridges which are loaded singly. The carbine, model of 1890, and the rifle, model of 1907-15, were also used to a considerable extent. These are magazine rifles, having a one-piece stock and a bolt with a turning head. They are loaded with a charger containing three cartridges. A box magazine was later designed for these rifles, increasing the capacity to five cartridges. Several