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.
M1941 Johnson machine gun The M1941 Johnson Light Machine Gun, also known as the "Johnson" and the "Johnny gun", was an American recoil-operated light machine gun designed in the late 1930s by Melvin Johnson. It shared the same operating principle and many parts with the M1941 Johnson rifle and the M1947 Johnson auto carbine.