The name came from the Birmingham Small Arms Company (BSA), who signed an agreement with Československá zbrojovka to manufacture the gun in the UK.

The British had intended to move from rimmed to rimless ammunition but with war imminent, wholesale change was not possible.

[4] The Mark II version, license-produced by BSA in Birmingham as opposed to ZB's Mk I, entered service in June 1940.

All those versions had a selector to give a high rate of fire (750–850 rounds per minute) for close combat or focused targets or a low rate of fire (450–550 rounds per minute) for long-range combat or area targets.

[8] It fired a 75 grams (1,160 gr) bullet from a 15×104 mm [ru] cartridge with a muzzle velocity of 818.3 m/s (2,685 ft/s) at a rate of 450 rounds per minute.