Inclination of Grooves

—Experience has shown that, as the velocity of rotation depends upon the form and initial velocity of the projectile, the causes which retard it, and the time of flight, there is a particular inclination of grooves which is best suited to each caliber, form of projectile, charge of powder, and angle of fire. The farther the centre of gravity of a projectile is in rear of the centre of figure, or resistance of the air, the greater must be the inclination of the grooves to resist deviation. It therefore follows that a conical projectile of the same length and diameter, requires a greater inclination of grooves than a cylindrical projectile, and the same will hold true for other forms as they approach one or the other of these extreme cases. The friction of the projectile as it pa es along the grooves, increases with their inclination; its effect will be to diminish the range and increase the strain on the piece, and the inclination may be carried so far as to break the projectile, or rupture the piece.