The Bren was a light machine gun intended to replace the previous Lewis Gun. Developed and put in production in 1935, BREN Mk.1 was a near identical copy of the Czech ZB-26, customized for United Kingdom standards and requirements (most notable - .303 British ammo). The Bren had a reduced rate of fire and heavy weight to aid controllability. The Bren was known to be reliable, but it had issues like barrel overheating too fast and the fact that it was magazine fed.