The modern center-fire metallic cartridges may be divided into three classes: the solid attached head, the solid head and the folded head. There are two varieties of folded-head cartridges, the reinforced and non-reinforced. As regards priming, the above-named classes are divided into outside and in side primed cartridges, and may be designated respectively as re-loading and non-reloading cartridges. They are generally made from sheet copper or brass. the latter material having more elasticity, and the former more uni formity and durability.
Manufacture—Sheet metal of the required thickness, from .c25 inch to .09 inch, is used for the various kinds of cartridges. This is fed to a double r.cting die and punch, which cuts out a disk and forms it into a cylindrical cup at one operation. The cup is reduced to a cylinder of the required length frcm four to six operations by dies and punches, and is called drawing or reducing. The cylindrical shell is trimmed to a standard length in a machine called the casc-trimmer. After washing, the shells or cases have a flange formed at the closed end by pressure in a special machine called the header.
The headed case is tapered to a standard size. The open end is made cylin drical for the length the bullet enters it, so as to inclose the latter snugly; and if it be inside-primcd, like the present service cup-anvil cartridge, the anvil is inserted and fastened at the same time by crimping the case around its edge.
Priming is done in a machine called the primer. For outside priming a percussion-cap is used, made in the ordinary way. Priming of fulminate of merculy sbould not under any circumstances, be deposited on brass. as it forms an amalgam, and rapidly deteriorates the metal and Priming. Shellac varnish is used to protect the surface of brass. No injurious deterioration front this cause I as been noticed in the use of copper.
Among the first of metal cartridges of Atnerican invention is the Morse, which was brought out a short time before the war of the rebellion, but not thoroughly experimented with at the time or introduced into service. Its objectionable features are apparent in the light of progress made. Its merits over paper or similar ammunition are apparent, the chief, perhaps, being that it was designed as a self-primed cartridge, had a flanged-head for extract irg the case, and that it reduced the operations of loading.
About the same time the Burnside, Maynard and a few others were pro duced, some of which were good in their day and for the arms for which they were designed, but were fired by means of a cap, through a vent, at some dis tance from the cartridge, and were extracted by the fingers. With them there
was not that necessary nicety of fit to the chamber of the gun, the joint was not absolutely closed, and the failures to explode were as frequent as with the old-fashioned paper cartridge and percussion-cap. Such failures would, nowadays, be considered a most unwarranted percentage in any metallic am munition laying claim to excellence, and, in the best known varieties, do not occur to the extent of one in one thousand rounds; in fact, many. attain a much higher standard of surety than indicated by this figure. The records of the testing-rounds show long-continued firing and consumption of thou sands of rounds without failure at all from any cause, and the summation of a year's practice and test, in proof of manufacture, exhibits but an exceed ingly small percentage of such failures.
For some time the idea of combining the primer and cartridge did not ass .rt itself. but some inventions were pushed in this direction, and the rirn pr med cartridg-e was produced. In this the fulminate composition was placed in the folded head of the case. This mode of priming requires a large charge of the priming composition, which, being thrown into the fold by swiveling, the entire circumference of the head was not always primed thor oughly, and as the cartridge is exploded by striking the rim at a part of the head under the hamtner, it not infrequently happened that it failed from the Rohn struck not having any priming. The large charge required, also (about five grains against one-half grain for the center-fire), was a further objection to rim-priming; the exploding of so large a quantity of quick powder in the folded head, the weak part of the cartridge, tending to strain and open the fold to bursting, as it frequently did. Another objection to rim primed cartridges is that they are more liable to accident in handling, and in shock of transportation, and in those incident to service; in fact, a number of instances of explosion in the magazine of repeating-arms, and in patent car tridge-boxes for service of such, have been reported, by which serious injury resulted to the soldier.