The Bofors had a curious introduction to naval service as it was originally adopted by the Army (a fortunate change of mind; the 2pdr was initially selected instead). Its obvious qualities led to its adoption by the Navy in 1941, the first ships equipped being the Prince of Wales, Nelson, Manchester and Erebus. These guns, and many others fitted to warships, were of the air-cooled Army pattern only slightly modified for Naval use and the single mountings weighed between 1,200 and 1,400kg; about the same as the 2pdr.
The air cooling obviously limited the continuous rate of fire (the 2pdr, and even the 5in Vickers, were almost invariably water--cooled although the Oerlikon was not). The Navy therefore adopted the twin-barrelled water-cooled Hazemeyer mounting of Dutch origin, the first RN vessel so equipped being the Whimbrel in November 1942. This was a complex mounting, triaxially stabilised so that the guns would (at least in theory) be held on target regardless of ship movement, but it weighed over 7,000kg and was not noted for reliability. Towards the end of the war the simpler and lighter (6.500kg) Mk V twin mounting was developed instead and this became the standard postwar twin mounting.
Water-cooled Bofors guns were also supplied from the USA in both twin and quadruple mountings, weighing about 6,000 and 11,000kg respectively. Finally, mention must be made of two British mountings which did not see service until after the War; the six-barrel Mk VI, fitted in Vanguard, which weighed nearly 22,000kg, and the awesome 15,000kg twin STAAG, a sort of "Super Hazemeyer" with its own on-mount radar. The theoretical performance of this mounting did not compensate for its weight and complexity and it did not long survive.
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