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?
9×19mm Parabellum The 9×19mm Parabellum, also known as 9 mm Luger by the C.I.P. or 9 mm NATO by NATO (abbreviated 9mm, 9mmP, 9×19mm or 9×19) is a cartridge that was designed by Georg Luger and introduced in 1902 by the German weapons manufacturer Deutsche Waffen und Munitionsfabriken (DWM) (German Weapons and Munitions Factory) for their Luger semi-automatic pistol.
9×23mm Winchester The 9×23mm Winchester is a pistol cartridge developed as a joint venture by Winchester Ammunition and Colt's Manufacturing Company. The 9×23mm Winchester has a convoluted development history, but was commercially introduced by Winchester in 1996. Marketed primarily to competition shooters as a replacement for .38 Super for International Practical Shooting Confederation, United States Practical Shooting Association and International Defensive Pistol Association competition, the cartridge made a splash, but never really caught on.