How a German MP-40 Works 

Wikipedia: The MP 40 (Maschinenpistole 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 (particularly platoon and squad leaders), and by paratroopers, on the Eastern and Western Fronts as well as armoured fighting vehicle crews.[5][6] 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 called "Schmeisser" by the Allies, after Hugo Schmeisser, who designed the MP 18, although he was not involved in the design or production of the MP 40. The weapon's other variants included the MP 40/I and the MP 41. From 1940 to 1945, an estimated 1.1 million were produced by Erma Werke.
Type Submachine gun
Place of origin Nazi Germany
Service history
In service 1939-1945 (Nazi Germany)
1940-present (other countries)
Used by See Users
Wars
World War II
Greek Civil War
First Indochina War
1948 Arab-Israeli War
Korean War
Algerian War
Malayan emergency
Vietnam War
West New Guinea dispute
Rhodesian Bush War
Lebanese Civil War
Guatemalan Civil War
Yugoslav Wars
Iraq War (very limited)
Syrian Civil War (limited)
Russo-Ukrainian War (limited)
Production history
Designer Heinrich Vollmer
Berthold Geipel
Designed 1940
Manufacturer
Steyr-Mannlicher
Erma Werke
Haenel
Unit cost 57 ℛℳ (1940)
250 EUR current equivalent
Produced 1940-1945 (MP 40)
No. built 1,100,000 (estimated)
Variants
MP 36
MP 38
MP 40
MP 40/1
MP 41
Specifications
Mass 3.97 kg (8.75 lb)
Length 833 mm (32.8 in) stock extended/630 mm (24.8 in) stock folded[4]
Barrel length 251 mm (9.9 in)
Cartridge 9×19mm Parabellum
Action Straight blowback, open bolt
Rate of fire 500-550 rounds/min
Muzzle velocity 400 m/s (1,312 ft/s)
Effective firing range 100-200 m
Maximum firing range 250 m
Feed system 32-round detachable box magazine, 64-round with dual
magazines
Sights Hooded front blade