The term British Firearm can be summarized as the STEN, a four letter acronym. The STEN was a family of British submachine guns used extensively by British and Commonwealth forces during World War II and the Korean War. It was notable for its simple design, low production cost, and ease of use. The STEN was developed in 1941 and was used until the 1960s. It was chambered in 9mm Parabellum and had a rate of fire of 500 rounds per minute.