AM'MUNI'TION (Fr. amunition, probably by wrong division of hi munition into ('am-uni tioe; from Lat. ?unwire, to fortify, defend). A term which embraces all the ordnance stores used in the actual firing of guns of every sort and calibre, and which includes gunpowder, pro jectiles, primers, and their accessories. When the powder, projectile. and primer are so eom bitted in a single piece as to be ready for firing as soon as placed in the gun, the packages so formed are called fixed ammunition : the term is also extended to ammunition for large guns in which the powder is inclosed in a primed metallic ease, but loaded separately from the projectile. In small arms the ammunition is invariably of the fixed type. For heavy guns the ammunition is almost universally fixed for calibres of less than four inches. Above this, the practice is not uniform in all countries or in all classes of guns. In the United States Navy fixed ammunition is used in all calibres of guns up to and including that of four inches; guns of five-inch calibre, of models antedating 1809, arc also supplied with it; six-inch except those of 1890 and later models, have the powder charge put op in primed brass cartridge cases, but the projectile is separately loaded. In other services, army and navy, the rule was. and is, about the same. In the new United States Navy guns (model of 1899). fixed ammu nition is used for guns of four-inch calibre and less. No cartridge cases are used for the larger calibres. A new form of lock, which automati cally ejects the primer, assists to make the load ing with powder in bags quite as rapid as if it were incased in metal. The metallic cartridge cases used for fixed ammunition are now gen erally made of hard drawn brass of the best quality, stamped from sheets or plates of vary ing thickness, depending upon the calibre of the gun for which they are designed. The circular disk cut from the sheet or plate is first given the form of a shallow cup and then drawn out and pressed into finished shape. The cases usually have a rim around the base, but some have a groove, called a cannriure, sunk into and surrounding the base; the chief use of both rim and cannelure is to enable the extractor to take hold of and extract the empty ease after firing; but the rim also assists to hold the case in its proper position in the gun. The high velocity given the projectile in a modern gun entails the use of a relatively large charge of powder; to hold this, and to avoid undue length of case, which involves unnecessary weight and intro duces dillicnIties in connection with vibrations and pressures, the case is increased in diameter woo the powder and drawn clown to form a bot tle-neck where it grips the projectile. No paper cases are used for military or naval arms, but the cases for the ammunition of breech-loading shot-guns have the eylindi ieal portion of card board or papier-mache', the base being of brass formed in the manner already described.
Gunpowder (see EXPLOSIVES and GuNrownEal, the propelling force in all military weapons in general service (except pneumatic guns, which have a very limited use and are not generally approved for any purpose), is put up, for guns of large calibre, in bags made of some sort of cloth, usually serge. For convenience of hand
ling, the charges are divided into sections when the weight of the full charge exceeds one hun dred pounds. Powder charges, when in bags, are stowed in watertight copper tanks in com partments or buildings called magazines; on shipboard, magazines are placed below the water line, near the bottom of the ship, and as far away as practicable from the heat of boilers and engines. In fortifications the magazines for war service are below ground or behind ample protections. Fixed ammunition is stored in rooms similar to magazines, as are also projec tiles (q.v.). Powder charges, whether in metal lic eases or in bags, are ignited by primers; these are of four types: percussion, friction, electric, and combination (percussion and electric). Per cussion primers resemble miniature fixed ammu nition; those used in the United States Navy are about an inch long, one-fifth of an inch in diameter in the body, and enlarged considerably at the base; they contain seven grains of fine powder in the body, and a primer cap in the head, which will ignite when struck by the firing pin of the gnu lock. Friction primers are of the seine shape and size, but are ignited by the friction caused by drawing a serrated strip of metal through the fulminate in the primer head. Their use in the United States Navy has been discontinued, but they are still in some favor abroad. Electric primers differ from those already mentioned in being ignited by an electric spark instead of by friction or percussion. Sin gle and double wire systems are employed, but only the former is used in the United States Navy; in guns which do not use fixed ammuni tion the current, furnished by a dry battery, or the dynamo, passes through a single insulated copper wire into the prhner; there it encounters resistance in the shape of a bridge of platinum wire, and thence escapes through the metal of the primer to the gun and so to earth; in pass ing through the platinum bridge it heats the latter white hot and thus causes ignition. In guns using fixed ammunition, the electric primer is screwed er pressed into the base of the powder case; the current enters the primer through the electric primer connection, which is similar to the percussion firing pin, but is insulated in order to carry the current. The combination primer is being experimented with in Europe; in the United States Navy it is displacing the percussion and electric primers, as all new guns and powder cases are fitted to take it, and the old ones are being altered as opportunity offers. It may be ignited either by an electric current or by percussion. It is much larger than the older primers, being about two inches long and about as large around as a lead pencil.