What cartridge, also known as 9 mm Luger by the C.I.P. or 9 mm NATO by NATO, is used in the submachine gun the MP 40?
MP 40 The MP 40 ("Maschinenpistole 40") was a submachine gun chambered for the 9×19mm Parabellum cartridge. It was developed in Nazi Germany and used extensively by the Axis powers during the Second World War.
General-purpose machine gun A general-purpose machine gun (GPMG) is an air-cooled, fully automatic, belt-fed weapon with a quick change barrel that can be used in a variety of roles, from bipod- or tripod-mounted infantry support, to deployment as a helicopter door gun, or a vehicle-mounted support weapon. Modern GPMGs fire full-powered rifle cartridges such as the 7.62×51mm NATO, 7.62×54mmR, 7.5×54mm French, 7.5×55mm Swiss, 7.92×57mm Mauser, etc.