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The construction and operation of the debouchoir or fuze-setting machine are in general terms as follows (figs. 21 and 22) :

A hollow rectangular box contains in its forepart a fixed socket, threaded internally. A second movable socket (the shell holder) is threaded externally in its lower part so as to be screwed up or down

FIG. 22.

in the fixed socket, and formed internally to take the shoulders of the shell, the fuze projecting downwards through a hole in the bottom of the holder. Fixed about the middle of this movable socket is a gear-wheel, and internally, in its bottom, is a small mortise into which a tenon on the fuze engages so that the fuze and shell always occupy a fixed position in the holder. The shell is inserted nose downwards in the holder, secured by the mortise and tenon, and the holder is then, by means of suitable gear in the box operating the gear-wheel, screwed down into the fixed socket, carrying with it the shell and fuze, until the appropriate point in the worm scale of the fuze comes opposite a punching tool in the fixed socket, at which point the tool, operated by an external hand lever, punches the cover, lead tube and body as before described. The amount of screwing-in is determined by the number of turns (or fractions of a turn) of the holder gear-wheel, and the internal gear of the box which actuates this gear-wheel is so controlled by a handle on the top of the box that the position of the handle relatively to a dial 1 on the box exactly represents the position of the fuze scale relatively to the punching tool in the fixed socket. (In practice the handle is set and the holder socket screwed in first, the shell inserted and keyed next, and the actual punching comes last.)

The French service debouchoir is made with two sets of elements side by side having a common dial, corrector scale and setting han- dle, but separate punching handles. This enables two fuzed shells to be set simultaneously for the same time of burning or successively for different times as desired.

AUTHORITIES. No recent book descriptive of fuzes has been published, in the ordinary sense of the word. Information during the war period was circulated only amongst those professionally con- cerned. The information given above has been collected from various papers and memoranda of this kind, and chiefly from those supplied by the authorities of Woolwich Arsenal, to whom, and to Lt.-Col. G. O. Boase in particular, thanks are due. (C. F. A.)

MACHINE GUN, RIFLE AND PISTOL

Since 1910 rapid strides have been made in the improvement of old and development of new designs of ammunition for machine guns, rifles and pistols, principally due to the World War. The manufacture of small arms ammunition, used by the various nations, may be briefly described by outlining the operations necessary to produce a standard cartridge of any one country. In general, these operations would apply to the manufacture of any cartridge, although slight departures there- from would be necessary where the designs vary. The metallic components of a cartridge are the case, primer (without chemical composition) and bullet.

The Cartridge Case is made of cartridge brass which, as produced commercially, contains about 67 % copper and 33 % zinc. The brass is furnished in strips, coiled in convenient lengths, which are passed through automatic machines to produce metallic cups, from which the finished cases are evolved by a series of processes generally similar to those described for heavy gun cartridge cases.

The Primer, inserted in the head of the cartridge case, consists of a cap made of primer brass into which is inserted a percussion compo- sition usually weighing from -25 to -40 grain, according to the character of the composition. After the assembly of the components, the primer is subjected to a drying operation for a short time to

1 The zero of this dial is itself adjustable relatively to a fixed fuze- corrector scale. For the theory of the corrector see 2.692, par. 29 and footnote.

insure that no moisture remains in the chemical mixture. After inspection it is inserted into the primer pocket and a drop of shellac placed in the joint between the primer and the cartridge case to provide water-proofing.

The Bullet (unless it be of special type such as armour-piercing) consists of a jacket surrounding a core. This jacket is made from cupro-nickel which, as furnished commercially, contains from 80% to 85% copper and from 15% to 20% nickel. The cupro-nickel is furnished in coiled strips from which by automatic machines cups are produced. These cups are subjected to a series of drawing opera- tions after which the nose and profile of the bullet are formed by swedging processes. The core, of lead hardened with antimony or tin, may or may not be inserted before the bullet jacket is swedged to form. Finally, the composite bullet is resized and prepared for union with the cartridge case.

In assembling the complete round the primed cartridge cases are shellacked in the mouth for water-proofing, and are loaded by automatic machines with a propellant powder charge weighing from 40 to 50 grains. The bullets are then inserted into the mouths of the cartridge cases and secured by crimping the top edges of the cases into the cannelures provided (or otherwise, according to the design of the cartridge in question). Small arms ammunition of the various countries is designed and loaded to give muzzle velocities varying from 2,200 to 2,800 ft. per second, with maximum pressures never exceeding 60,000 Ib. (27 tons) per sq. inch. Cartridge clips for quick loading are used in some form with practically all magazine rifles. The number of cartridges in a clip is usually five, placed one above the other. These clips are usually made with a body of rust-proofed steel or brass containing a flat brass spring.

The loaded ammunition, after being weighed, inspected and clipped, is classified and packed according to its future use. In the United States, ammunition passed as suitable for both rifles and ground machine guns is packed for issue in bandoleers made of olive- drab cloth, which generally contain six boxes each holding two clips. In most armies such individual packets of ammunition are put up in larger, metal-lined boxes, the number of rounds packed in a box and therefore its weight varying in different countries according to the preferences of the military authorities in each.

Packing-boxes are provided with watertight metal liners. In the United States the packing-box when loaded with ammunition weighs approximately no Ib.; in Great Britain (mark VII. ammunition), 75 to 80 Ib.

A mmunition for Machine Guns may be divided into two general classes: first, that for use in machine guns on the ground; and second, that for use in aircraft machine guns. The extensive use of ammuni- tion for machine guns in the World War involved no new processes of manufacture in order to adapt it to the particular weapons. It did, however, require a more rigid inspection system in order to insure that the ammunition produced w^s of a quality suitable to stand the wear and tear of machine-gun action.

Ammunition for ground machine guns is generally the same as the standard type used in the shoulder rifle, but more rigidly inspected and tested. Several of the belligerents in the World War developed special types of cartridges having heavier bullets than their standard types for use in machine-gun barrage fire.

A number of special types of machine-gun ammunition have been developed for use by aircraft, all of which have the same overall length as the service ammunition and may be briefly described as follows :

The tracer cartridge, as the name implies, is loaded with a tracer bullet for use with machine guns where, as in aircraft work, it is essential to make the trajectory visible. The bullet differs materially from that of the service cartridge, in that the lead core of the latter is replaced by a conical lead slug in the nose of the tracer bullet jacket, in the rear of which there is inserted a gilding-metal capsule which contains the tracer composition. The ingredients used in the com- position are dependent upon the type of trace desired. The red tracer involves the use of strontium salts with the necessary oxidizing agents, while the so-called white tracer gives off a greenish-white flame and involves the use of the barium salts with oxidizing agents. The tracer composition is compressed into the capsule at a pressure to withstand that produced by the exploding cartridge and the length of trace can be regulated by the adjustment of the pressure or amount of oxidizing agents used in the chemical mixture. The composition is ignited by the propellant powder flash and burns with a bright light during a minimum of 500 yd. of flight. Tracer car- tridges are generally loaded so as to give the same ballistics as the service ammunition at 500 yards. As these cartridges are placed in machine-gun belts, interspersed with service, incendiary and other types of special aircraft ammunition, a distinctive marking is provided so that inspection may be made of each ammunition belt before the aviator goes into the, air.

Owing to the extensive use of observation balloons and dirigibles in the war, the demand was created for an incendiary bullet which