Rifling in the Bore

A bullet fired from a rifle or handgun has a spiral spin that keeps it point-first in flight, increasing accuracy and distance. This spin is achieved by the rifling inside the barrel, from which the rifle got its name. The barrel is thick and has spiraling grooves cut or pressed into the bore. The ridges of metal between the grooves are called lands. Together, the grooves and lands make up the “rifling.”

• The distance from the beginning of a groove to the point where the groove completes a full revolution in the bore determines the rifle’s twist rate. This rate will stabilize projectiles differently. As the length of the twist gets longer, the twist rate becomes slower. Slow twist rates tend to stabilize roundball bullets well, and fast twist rates tend to stabilize conical bullets more effectively. Some muzzleloading firearms have middle-of-the-road twist rates that will shoot either type of bullet fairly well.
• The diameter of the barrel, measured from land to opposite land, is its caliber.
• Shotguns, which have no rifling, are known as smoothbores.