Heckler_&_Koch_MP5 The MP5 (short for Maschinenpistole 5 or "machine pistol model 5") is a 9mm submachine gun of German design, developed in the 1960s by a team of engineers from the West German small arms manufacturer Heckler & Koch GmbH (H&K) of Oberndorf am Neckar. The company, encouraged by the success of the G3 automatic rifle, developed a family of small arms consisting of four types of firearms (all based on a common G3 design layout and operating principle), where the first type was chambered in 7.62x51mm NATO, the second—using the 7.62x39mm M43 round, third—the intermediate 5.56x45mm NATO caliber and the fourth type—chambering the 9x19mm Parabellum pistol cartridge.