Shotguns differ from rifles as they are uniquely able to fire shells containing pellets, shots, or slugs of different sizes and types. Unlike rifles, shotgun barrels are typically not rifled or grooved inside. There are two types of shotguns which differ in how they function. These are the pump-action shotgun and the semi-automatic shotgun.
Both of these use shotgun ammo, but the pump-action shotgun requires the user to move the slide backwards and forwards manually to load each shell. Semi-automatic shotguns use the force created by the previous shot to automatically eject the empty shell case and chamber the next round.