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.
.303 British The .303 British (designated as the 303 British by the C.I.P. and SAAMI) or 7.7×56mmR, is a .303 in calibre (with the bore diameter measured between the lands as is common practice in Europe) rimmed rifle cartridge first developed in Britain as a black-powder round put into service in December 1888 for the Lee–Metford rifle. In 1891 the cartridge was adapted to use smokeless powder. It was the standard British and Commonwealth military cartridge from 1889 until the 1950s when it was replaced by the 7.62×51mm NATO.