Mark I and Mark II The Mark I was the initial model but the gun went through further development before entering production and the first Mark to be taken into service was the Mark II. The Mark II entered service in 1933 and was mounted in some British light tanks, often paired with a 0.303 Vickers. The Mark II had a pistol grip rather than the spade grips of the infantry 0.303 machine gun.
Mark III (1940) The Mark III was a naval version used as an anti-aircraft weapon, mostly by the Royal Navy and allied navies in the Second World War, typically in mountings of four guns but also as single and dual mounts. It proved insufficiently powerful at short-range against modern all-metal aircraft and was superseded during the Second World War by the
Oerlikon 20 mm cannon. The naval quad mount featured a 200-round magazine per barrel, which wrapped the ammunition belt around the magazine drum. Maximum rate of fire of fire was 700 rounds per minute, per gun (cyclic) but could be reduced to 450. The four-barrel mounting had its guns adjusted to provide a spread of fire, amounting to wide and high at . The Mark IV was introduced in 1933 but not declared obsolete until 1944. It had full auto only at 600 rounds per minute. The Mark V, introduced in 1935, was a strengthened variant and the main variant to be used. Fire rate was 500-600 rounds per minute. ==See also==