A shotgun shell, shotshell or simply shell is a type of rimmed, cylindrical (straight-walled) cartridges used specifically in shotguns, and is typically loaded with numerous small, pellet-like spherical sub-projectiles called shot, fired through a smoothbore barrel with a tapered constriction at the muzzle to regulate the extent of scattering. A shell can sometimes also contain only a single large solid projectile known as a slug, sometimes fired through a rifled slug barrel. The hull usually consists of a paper or plastic tube often covered at the base by a metallic head cover which retains a primer, and the shot charge is typically contained by a wadding/sabot inside the case. The caliber of the shotshell is known as its gauge.
The projectiles are traditionally made of lead, but other metals such as steel, tungsten and bismuth are also used due to restrictions on lead, or for performance reasons such as achieving higher shot velocities by reducing the mass of the shot charge. Other unusual projectiles such as saboted flechettes, rubber balls, rock salt and magnesium shards also exist. Slug shells can also be made with specialty non-lethal projectiles such as rubber and bean bag rounds.
