What type of firearms have a barrel that is smooth instead of rifled?

Shotguns have smooth barrels rather than rifled ones. This design is intentional and allows shotguns to fire multiple pellets or a single slug effectively. The smooth barrel helps in dispersing the shot over a wider area, which is particularly useful in hunting birds or other small game where precision at long distances may not be as critical as with other firearms.

In contrast, rifles and semi-automatics are designed with rifled barrels, which have spiral grooves that impart spin to the bullet. This spin stabilizes the projectile, resulting in greater accuracy over distance. Revolvers, while they can also have rifled barrels, still follow this same principle. Therefore, the main distinction of shotguns lies in their smooth barrels, making them a unique category of firearm that serves different purposes compared to those with rifled barrels.