Rifle System

—Spiral grooves are cut into the bore of the piece, or it is ribbed with spiral bands, and the projectile is so formed or prepared as to follow them as it pa es along the bore of the piece. The principal question which now occupies the attention of those engaged in improving this species of cannon is to obtain the safest and surest means of effecting this object. Various plans have been tried to obtain the proposed object; nearly all may be ranged under the following heads: 1. The Flanged System. —This comprises all projectiles which have certain flanges or projections to fit into the grooves of the gun in loading. These are usually deep and few in number, rounded at their bottom edges so as to cause the flanges or studs to pa up the inclined side when rotation is imparted. This is the system at present adopted in England. Though this plan affords a certain means of communicating the rifle motion, it has not always been found a safe one, probably from the wedging of the flanges in the grooves. Besides, the dirt from the burning of the powder collects in the grooves; and as it is difficult to clean them by the usual means, the projectile is liable to meet with obstruction in loading. To obviate these difficulties, the flanges are sometimes made of softer metal than the body of the projectile. Guns for flanged or studded projectiles usually have from 3 to 9 grooves, 0.15 to 0.25 inch deep. 2. The Compre ive System. —By this system the projectile is forced by the action of the powder through the bore of a piece whose diameter without the grooves is le than the diameter of the projectile. Such are the projectiles for the breech-loading Krupp and Broad well guns. These usually consist of cast iron or steel, and are covered with a coating of lead or other soft metal having horizontal ribs or corrugations, which is secured by a chemical solder, or cast into undercuts in the body of the shot. As the projectile is forced through the bore, an impre ion of the rifling is cut out of the ribs, the lead thus displaced finding room in the grooves between. This system has been found to work satisfactorily in breech-loading guns. The rifling should be shallow and consist of numerous grooves, slightly narrowing towards the muzzle. Large guns usually have from 20 to 76, from.05 to.08 inch deep. Experiments are now being made, with prospects of succe , to substitute bands of soft copper encircling the projectile for the lead coating. 3. The Expansive System. —This system has been so exclusively used in the United States that it has frequently been called the American system. It embraces all projectiles which are loaded without regard to the rifling, but which are fitted with an expanding portion of some softer metal, as pewter, copper, wrought iron, or papier-maché , which is forced into the grooves by the discharge. This system requires for its rifling fewer grooves than the compre ive, but a somewhat greater number than the flanged system. Among the projectiles of this cla used during the civil war were the Blakely, Dyer, Hotch ki , James, Parrott, Reed, Schenkle, and Stafford. The principal objections to an expanding or compound projectile are its want of strength to resist a charge of powder proportionately as large as that employed for a simple projectile, and the danger of its breaking and wedging in the bore of the piece. Of late years, however, marked improvements have been made, and projectiles of this cla can now be safely fired with double their former charges. The large projectiles of this description now used in the United States consist of the usual cast-iron body having a sabot, or ring of bra or copper either cast or screwed to its base. This ring is divided into an upper and lower flange or lip by an annular groove. When the gun is fired, the gases enter this groove, forcing the lower flange down upon the projectile and the upper or outer into the rifling of the gun, where it is kept during its pa age through the bore.