smoothbores

Smoothbore refers to a firearm or artillery barrel that lacks rifling, the helical grooves that impart spin to a projectile. In a smoothbore, projectiles do not receive gyroscopic stabilization from the bore; stability relies on the projectile's design, muzzle velocity, and the type of ammunition. The term contrasts with rifled barrels, which have grooves that twist the projectile for improved accuracy at distance.

Historically, smoothbore muskets and arquebuses dominated early firearms. From the 16th through the 19th century, most infantry weapons were smoothbore, fired round lead balls or buckshot. The development of rifling in the 17th and 18th centuries gradually increased the effectiveness of rifled firearms, eventually supplanting most smoothbores in military service. In the 19th century, the introduction of breech-loaders and cartridges continued to favor rifled designs, though smoothbores remained in use for shotguns and some artillery.

In modern small arms, smoothbores are synonymous with shotguns, which fire shells containing multiple pellets or a single slug. The lack of rifling creates a wide, predictable pattern at close range, useful for hunting birds and clay-target shooting. Shotgun barrels can be fitted with choke tubes to control shot spread. Ammunition is measured by gauge (for example, 12 and 20 gauge). Slugs are also used in smoothbores to improve downrange accuracy for certain hunting applications.

In artillery, smoothbore guns were common in the early and mid-20th century; many large-caliber weapons transitioned to rifling to stabilize fin-stabilized projectiles. Nevertheless, some modern systems retain smoothbore designs for specific ammunition types, including certain high-velocity, fin-stabilized rounds that do not require spin.