smoothbore

A smoothbore is a firearm whose bore lacks rifling, resulting in a smooth interior surface. The absence of grooves means that projectiles are not given deliberate spin by the barrel, so stabilization is achieved through the design of the projectile itself or the firing load, such as multiple pellets in a shotgun shell or a slug.

Historically, smoothbores were standard in early firearms, including muskets and many artillery pieces. These weapons fired round balls or shot without any spin, which limited long-range accuracy but offered effective close-quarters performance and simpler manufacturing. The development of rifling in barrels substantially improved stabilization and accuracy, leading to the gradual replacement of many smoothbores in infantry use by the 19th century. Nevertheless, smoothbores remained in specialized roles where a wide shot distribution or certain ammunition types were advantageous.

Modern usage encompasses several domains. Shotguns are by far the most common smoothbore firearms, optimized for firing shells that break into multiple pellets or a single slug, providing a wide impact pattern at close range. In artillery and naval guns, smoothbores have persisted in some designs due to compatibility with certain types of ammunition, such as fin-stabilized projectiles or large-volume shock effects. Some modern large-caliber systems also employ smoothbores when their intended projectiles do not require spin stabilization, while many contemporary small-arms rifles rely on rifling for accuracy over longer distances.

Overall, smoothbores are defined by their lack of internal spiraling grooves and are selected for specific tactical advantages tied to ammunition type and intended engagement envelope.