The MP 40 is a submachine gun chambered for the 9×19mm Parabellum cartridge. It was developed in Nazi Germany and used extensively by the Axis powers during World War II. Designed in 1938 by Heinrich Vollmer with inspiration from its predecessor the MP 38, it was heavily used by infantrymen, paratroopers, platoon and squad leaders on the Eastern and Western Front. Its advanced and modern features made it a favorite among soldiers and popular in countries from various parts of the world after the war. It was often erroneously called "Schmeisser" by the Allies, despite Hugo Schmeisser's non-involvement in the weapon's design and production. From 1940 to 1945, an estimated 1.1 million were produced. by Erma Werke.
The MP 40 submachine guns are open-bolt, blowback-operated automatic arms. Fully automatic fire was the only setting, but the relatively low rate of fire allowed for single shots with controlled trigger pulls.
The bolt features a telescoping return spring guide which serves as a pneumatic recoil buffer. The cocking handle was permanently attached to the bolt on early MP 38s, but on late production MP 38s and MP 40s, the bolt handle was made as a separate part. It also served as a safety by pushing the head of handle into one of two separate notches above the main opening; this action locked the bolt either in the cocked (rear) or uncocked (forward) position. The absence of this feature on early MP 38s resulted in field expedients such as leather harnesses with a small loop, used to hold the bolt in forward position. Visit Wikipedia.