GUN MAKING. The manufacture of mus kets and fowling-pieces is carried on to a very large extent at Birminghani. More than five million pieces of fire-arms were made in that town between 1804 and 1818. Yet there are no gun-factories properly so called. The same gun travels about from factory to factory, from shop to shop, before it is finished.
The most essential part of a gun is the barrel. The interior of the barrel is usually a smooth cylinder, but the exterior is made slightly conical by thickening the metal at the breech or hinder end. The com moner barrels are formed of tenacious soft iron, which is rolled into the form of flat bars, called skelps, each of which is sufficient to form a single barrel. The length of a skelp is usually about three feet, and the breadth about four inches at one end, and two and a half at the other. In welding these skelps into barrels, the thicker end is heated to red ness, and hammered upon a hollow cavity in an anvil until the edges are turned up. A mandril being then inserted in the concavity between them, the edges are turned over and welded together. The skelp is thus gradually converted into a tube or barrel, after many beatings and hammerings. This laborious process of welding is now to a great extent superseded by improved methods. In one of these methods, the barrels, instead of being formed of skelps forged to the length of the barrel, are made from slabs of refined bar iron, ten or twelve inches long, and weighing from 10 to 11 lbs. Each slab, by being heated and passed between rollers of a peculiar shape, is bent round into a tubular form; and re peated drawings between other rollers weld the two edges firmly together, and at the same time elongate the tube to the proper dimen sions, a mandril being placed inside to pre serve the bore of the barrel. The above pro cesses are for plain barrels. Twisted barrels are made of long and very narrow strips of iron ; one of which, being moderately heated to increase its pliancy, is wrapped spirally round a cylindrical mandril, in such a way as to form a tube, which may be slipped off the mandril at pleasure. As the rods are not usually made of sufficient length for one to form a barrel, several are usually joined end to end, those which form the breech being thicker than those at the muzzle end. By
heating • and hammering, these pieces are welded into a continuous and very strong and tough tube. Partially worn or ' scrap ' iron is preferred for these purposes. The twisted barrels, technically termed wire- twist, are formed of narrow rods of compound metal, composed of alternate bars of iron and steel forged into one body, and then rolled out to the requisite tenuity. Damascus barrels are composed of similar metal, but the rods are twisted upon their own axes until their com ponent fibres have from twelve to fourteen turns in an inch, and the rods are thereby doubled in thickness and proportionately re duced in length. Two such rods are welded together side by side, their respective twists being reversed. The varieties in the modes of making twisted barrels are very numerous.
After welding, the barrels are carefully exa mined, and, if needful, straightened by a few blows of the hammer. They are then bored in a machine with an angular plug of tempered steel, which is caused to revolve rapidly within the barrel, a stream of cold water being directed upon the outside to check the heat generated by the excessive friction of the tool. The out side is brought to a smooth surface either by grinding on a large grindstone or turning in a lathe. The breech end of the barrel is tapped with a screw-thread, to receive the breech-plug, which closes it at that end.
The barrels are then ready for proving, which consists in firing them in a building in which their explosion can do no harm, with a charge four or five times as great as they will have to bear when in use. A great number of barrels are fired at once, by laying them upon a strong framework of wood, with their touch-holes downwards, and connected with a train of powder which is conducted outside the build ing, within which is laid a heap of sand to re ceive the bullets. They are then carefully examined, and such as show any defect are returned to be reforged, after which they must be proved again, while such as have stood the test satisfactorily are stamped with a distin guishing mark.