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Barrel

Barrel types include rifled —a series of spiraled grooves or angles within the barrel—when the projectile requires an induced spin to stabilize it, and smoothbore when the projectile is stabilized by other means or rifling is undesired or unnecessary. Typically, interior barrel diameter and the associated projectile size is a means to identify gun variations. Bore diameter is reported in several ways. The more conventional measure is reporting the interior diameter (bore) of the barrel in decimal fractions of the inch or in millimetres. Some guns—such as shotguns —report the weapon's gauge (which is the number of shot pellets having the same diameter as the bore produced from one English pound (454g) of lead) or—as in some British ordnance—the weight of the weapon's usual projectile.