Centring

—In consequence of the windage nece ary in all muzzle-loading guns, the axis of the projectile does not always coincide with that of the bore in firing. This leads to inaccuracy of fire. A projectile is said to be centred when the grooves of the rifling are so constructed as to bring the axis of the projectile on a line with that of the bore when the piece is fired. There are several ways of accomplishing this, among them Armstrong’s method called “Shunt rifling.” See Armstrong Gun under Ordnance, Construction of , the Krupp , and others.