A submachine gun is a type of machine gun. In particular, a submachine gun is a machine gun which fires ammunition normally used in pistols. Other characteristics distinguishing them from other machine guns include: light weight, a short barrel, and an inability to fire for sustained lengths of time (due to small magazine and a tendency to overheat quickly). They have typically been issued to special commando forces in the military. Their basic function is for fighting at close range like house fighting where a weapon's range is less important than the ability to easily hit and neutralize a target.
Prominent examples include the Thompson submachine gun, Israeli Military Industries Uzi submachine gun, and the Heckler und Koch MP5 series.
In the United States, submachine guns have been categorized as Class III weapons, not available to the general public without special permits, since the 1934 National Firearms Act.
Compare machine pistol, carbine.
See also: Blowback, Firearm action