MACHINE GUN. 621 MACHINE GtTN. is loaded in turn, and so on until the ammuni- tion is exliausted. The guns of Class B that are now in use are (1) fully automatic, or (2) semi-automatic. A gun is not automatic if it is operated by the rotation of spindle worked by hand, clockwork, or by motor: for the evident reason that the operating power is obtained from an outside or external source. But, if the power is derived from the explosion of a preceding cartridge, the gun would come under the heading of powder gas acting on the lug throws it back with force sufficient to give power to carry on all the operations of loading and firing. The gun has no water jacket, but the barrel is very heavy (more than an inch in diameter). The car- tridges are fed in a belt of woven cotton which carries 250: additional belts may be placed in position with the loss of but a few seconds' time. The gun used in the United States Xavy has a calibre of 0.23G or 0..30 inch, and weighs 40 to 42 pounds. It is usually mounted on the DETAIL OF COLT AUTOMATIC GUS. B. barrel : C. breech casing? : D. operating: rod ; E, carrier which lifts cartridge in front of breech bolt : P, feed mechanism : G. gas cylinder in which gas-piston (P) flt.s ; H, liammer : K. band aronnd barrel carrying double lugs in which is pivot of gas lever (L): L, gas lever which is made to vibrate and operate mechanism : M. o[>ening in cas- ing for feed belt ; N, pivot of operating rod (D) on gas lever : O. gas lever pivot in lugs of band (K): P. gas piston against which powder gas acts: R, short arm on end of gas lever (L) to which are attached springs fS) to return (L) to position aft*r firing: S. springs to lieep gas lever up; C, pivot of operating rod : V, vent through which gas escapes ; AV, trigger ; X, eliding bar which works breech bolt, feed mechanism, and carrier ; Z, breech bolt. automatic machine guns, and thus be differ- entiated from those operated by a crank worked by hand, or a 'motor machine gun' worked by an electric or other motor. The term semi-auto- matic when applied to ordnance is used to denote any gun in which the functions necessary to its employment are performed partly automatically and partly by external agents. The fully auto- matic guns may be divided into (la) those op- erated by the powder gas acting upon a piston, and (lb) those operated by the recoil of the barrel or other parts when the piece is fired. All ship's rail or on the rail of a top. For .service in the field a tripod mount weighing .50.2.5 pounds is supplied. The speed of fire is about .100 rounds per minute, but, owing to the necessity of changing the belt, about 2.50 is the practical limit. The Hotchkiss and Yam.anouchi guns dif- fer from the Colt chiefly in the method of uti- lizing the pressure of the powder gas. Instead of pressing against a vibrating lever, the powder gas e.seapes from the hole in the barrel into the end of a cylinder underneath and presses back a piston which works the mechanism. As soon as HOTCHKISS KIFLE-rALIBRE AUTOMATIC OrN OS TBIPOD. semi-automatic pieces so far produced are oper- ated by the recoil of the barrel or moving parts. The fully automatic guns of the la class are very numerous, but those best known are the Colt (Browning's patent). Hotchkiss, and Yamanouchi (.Japanese). The mechanism of the Colt gim is driven by the action of a vibrating lever which is pivoted on the gun and has a short cylindrical lug at its forward end resting in a socket in the casing and covering a hole in the barrel near the muzzle. When the bullet passes "beyond the hole in the barrel the pressure of the the bullet leaves the muzzle the pressure against the piston is removed and it is free to come forward again and is returned by the action of a spring. The guns of the (lb) type are quite numerou.s. but the Maxim automatic gun. the Maxim - Xordenfcldt automatic 1 - pounder, to which the name of Pompom was given in the British-Boer War (1890-1902). the Dawson-Sil- verman (Vickerst automatic .3-poundor. and the Skoda automatic gun are well known. In all .except the Dawson-Silverman 3-povinder the re- coiling barrel or breech-lock drives a train of
