Illustration: FIG. 11. MACHINE FOR MAKING MINIÉ RIFLE BULLETS.
Illustration: FIG. 1. MUSKET BORING.
Illustration: FIG. 2. RIFLING PROCESS.
In the manufacture of fire-arms the chief parts consist of the metal
tube from which the projectiles are to be expelled, the stock of
the musket and the carriages of great guns or cannon being only
varieties of the same thing, namely a convenient platform from which
to fire the tube, which is the real instrument. In the manufacture of
muskets, pistols, and cheap fowling-pieces, the barrel is made from
a sheet of soft iron rolled up lengthwise round a rod or “mandril,”
the edges overlapping each other, which are then welded together; but
in the best guns the barrels are twisted, that is, a slip or fillet
of iron half-an-inch broad and of sufficient length is twisted in a
spiral round the mandril, and then the whole is welded together. The
barrel is “bored” by means of a square-headed drill of steel turned
in a kind of lathe (fig. 1), and the interior afterwards polished
with oil and emery-powder until it is perfectly bright and even; the
breech is then made separately, and screwed in. The best iron for
gun-barrels is called “stubb iron,” consisting of old horse-shoe
nails welded together, and is very soft and even in its grain. The
barrel is made red-hot and suffered to cool very slowly; this is
called “annealing,” and it prevents any part being brittle, and
therefore liable to burst with the charge in firing. Rifled barrels
are those which have one or more grooves cut in the inside of the
barrel from the muzzle to the breech in a spiral direction, each
making one turn before it completes the length of the barrel (fig. 2).