machine-pistol

A machine pistol is typically a handgun-style, magazine-fed, self-loading firearm, capable of fully automatic or burst fire, and chambered for pistol cartridges. The term is a literal translation of Maschinenpistole, the German term for a hand-held automatic weapon firing pistol cartridges.
While the dividing line between machine pistols and compact submachine guns is hard to draw, the term "submachine gun" usually refers to carbines designed for automatic fire of pistol cartridges, while the term "machine pistol" usually refers to a weapon built up from a semi-automatic pistol design, through use of a modified "fire control group", and which usually includes a modified "disconnector" and a selector which either enables (semi-automatic mode) or inhibits (fully automatic mode) the conventional, semi-automatic operation of the "disconnector".
Machine pistols are generally more compact to be concealable and can be operated one-handed, while submachine guns are usually designed to be two-handed and tend to have longer barrels for better accuracy. A current production machine pistol is the Glock 18, which is a relatively simple enhancement of the Glock 17, upon which it is largely based. Unlike firearms which were designed from the ground-up to be selective-fire, the Glock 18 includes only semi-automatic and fully automatic modes, and does not have the 3-shot "burst" count capability which is quite common on many selective-fire weapons.
As a small, concealable weapon with a high rate of fire, machine pistols have numerous applications. Bodyguards from government or private agencies sometimes carry concealed machine pistols when they are protecting high-risk VIPs. Criminal gang members such as narcotics traffickers also use machine pistols, often cheaper guns such as the MAC-10 or the Tec-9 which have been illegally converted to fire in a fully automatic fashion. In a law enforcement context, machine pistols may be used by tactical police units such as SWAT teams or hostage rescue teams which are operating inside buildings and other cramped spaces, although they tend to use submachine guns instead.
In a military setting, some countries issue machine pistols as personal defense side arms to infantry, paratroopers, artillery crews, helicopter crews or tank crews. They have also been used in close quarters combat (CQC) settings where a small weapon is needed (e.g., by special forces attacking buildings or tunnels). In the 2000s, the machine pistol started to be supplanted by the personal defense weapon: a compact, fully automatic submachine gun-like firearm which fires high-velocity armor-piercing rounds instead of pistol ammunition.

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