The MP 40 is a submachine gun developed by Nazi Germany in 1940. Chambered for the 9x19mm Parabellum cartridge, it was widely used by the Axis powers during WWII. The MP 40 was designed by Heinrich Vollmer in 1938 and was inspired by its predecessor, the MP 38.
Open-bolt and blowback-operated, the MP 40’s only mode of fire was fully automatic. However, because of the low rate of fire, single shots could be enabled with controlled trigger pulls. It also featured a forward-folding metal stock, the first for a submachine gun. Overall reliable, the MP 40 was used for several decades after WWII by countries around the world.