IMPORTANCE OF RIFLING

In a rifle the grooving is of the utmost importance; for velocity without accuracy is useless. To determine
the best kind of groove has been, accordingly, the object of the most laborious investigations. The
projectile requires an initial rotary motion sufficient to keep it spinning up to its range, and is found to
gain accuracy by increasing this rotary speed. If the pitch of the grooves be too great, the projectile will
refuse to follow them, but being driven across them, strips the lead in the grooves is torn off, and the ball
goes on without rotation.

The English gunsmiths avoided the dilemma by giving the requisite pitch and making the Rifling grooves
very deep, and even by having wings or lugs cast on the ball to keep it in the grooves expedients which
increase the friction in the barrel and the resistance of the air enormously.

The American gun-makers solved the problem by adopting the gaining twist, in which the grooves start
From the breech clearly parallel to the axis of the barrel, and gradually increase the spiral, until, at the
muzzle, it has the pitch of one revolution in three to four; the, pitch being greater as the bore is less. This
gives, as a result, safety From stripping, and a rapid revolution at the exit, with comparatively little
friction and shallow groove marks on the ball, accomplishing what is demanded of a rifled barrel, to a
degree that no other combination of groove and form of missile ever has.

There is no way of rifling so secure as that in which the walls of the grooves are parts of radius of the
bore. They should be numerous, that the hold of the lands, or the projection left between the grooves,
may divide the friction and resistance as much as possible, and so permit the grooves to be as shallow
as may be.