This means the bolt remains to the rear when the weapon is cocked, and on pulling the trigger the bolt moves forward under spring pressure, stripping the round from the magazine, chambering it and firing the weapon all in the same movement. The Sten is a blowback-operated submachine gun firing from an open bolt with a fixed firing pin on the face of the bolt. They had a simple design and very low production cost, so they were also effective insurgency weapons for resistance groups. The STEN (or Sten gun) was a family of British submachine guns chambered in 9×19mm and used extensively by British and Commonwealth forces throughout World War II and the Korean War.
