The Probert Encyclopaedia of Warfare

SHOTGUN

A shotgun is a shoulder gun with smooth-bored barrel(s) primarily intended for firing multiple small, round projectiles, (shot, birdshot, pellets), larger shot (buck shot), single round balls (pumpkin balls) and cylindrical slugs. Some shotgun barrels have rifling to give better accuracy with slugs or greater pattern spread to birdshot.
Research Shotgun