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.
6.5×55mm The 6.5×55mm (designated as the 6.5×55 Swedish by the SAAMI and 6,5 × 55 SE by the C.I.P.) is a first-generation smokeless powder rimless bottlenecked rifle cartridge. Other, less common names are 6.5×55mm Swedish Mauser, 6.5×55mm Mauser and 6.5×55mm Krag. It was developed in 1891 for use in the new service rifles then under consideration by the United Kingdoms of Sweden and Norway. The two nations had independent armies and consequently the normal procedure at the time was for their respective governments to use the same ammunition and then purchase small arms of their choice. Norway adopted the Krag–Jørgensen rifle, while Sweden adopted a Mauser rifle design.