Vickers .50 machine gun

The Vickers .50 machine gun, also known as the 'Vickers .50' was similar to the Vickers machine gun but enlarged to use a larger-calibre round. It saw some use in tanks and other fighting vehicles but was more commonly used as a close-in anti-aircraft weapon on Royal Navy and Allied ships, typically in a four-gun mounting. The Vickers fired British .50 Vickers (12.7×81mm) ammunition, not the better known American .50 BMG (12.7×99mm).
Mark I.
The Mark I was the development model.
Mark II, IV and V.
The Mark II entered service in 1933 and was mounted in some British tanks. Marks IV and V were improved versions and were also used on trucks in the North Africa Campaign. It was superseded for use in armoured fighting vehicles (AFVs) during the Second World War by the Besa.
Mark III.
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 4 guns. It proved insufficiently powerful at short-range against modern all-metal aircraft and was superseded during the Second World War by the Oerlikon 20 mm cannon.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 and provided a maximum rate of fire of 700 rounds per minute, per gun. The four-barrel mounting had its guns adjusted to provide a spread of fire, amounting to wide and high at . Vickers claimed that it could fire all 800 rounds in 20 seconds and could then be reloaded in a further 30 seconds. During the Second World War it was also mounted on power-operated turrets in smaller craft such as motor gunboats and motor torpedo boats.