Implacable-class aircraft carrier Aircraft carrier Destroyer Ships with 4.5 inch guns QF Mark III in twin mounting BD Mark II** Audacious-class aircraft carriers, HMS Eagle and HMS Ark Royal Ships with 4.5 inch guns QF Mark III in twin mounting BD Mark IV Battle-class destroyer Nueva Esparta-class destroyers D-11 Nueva Esparta, D-21 Zulia and D-31 Aragua Ships with 4.5 inch guns QF Mark IV in single mounting CP Mark V Destroyer Z-class destroyers Ca, Ch, Co and Cr-class destroyers "1942" Battle-class destroyers Ships with 4.5 inch guns Mark 5* (rebuilt mounting CP Mark V). Rebuilt Ca-class destroyers (Mark 5* Mod 1) Type 81 Tribal-class frigates (Mark 5* Mod 2) Ships with 4.5 inch guns QF Mark V in twin mounting UD Mark VI (later renamed gun Mark 6) Battle-class destroyers - "1943" or "Australian Battle" class Daring-class destroyers County-class destroyers Type 12 Whitby-class frigates Type 12I Rothesay-class frigates Type 12M Leander-class frigates Van Speijk-class frigates - Netherlands Navy versions of Leander class River-class destroyer escorts - Australian versions Condell-class frigates - Chilean versions Type 41 Leopard-class frigates Type 61 Salisbury-class frigates Land service QF Mark II was a single gun mounting (Mounting Mk 1) anti-aircraft gun in static sites. The pedestal mount was bolted to concrete in an unarmoured turret, a travelling platform was available to transport the gun and mounting between positions. The first unit became operational in February 1939. These 16.5 ton anti-aircraft mountings had a maximum elevation angle of 80 degrees. However, most mountings were Mark 1A with an elevation range of -9.5 to 80 degrees. This enabled the gun to be dual role (anti-aircraft and coastal defence) in coastal areas. Armour piercing rounds were provided for anti-ship engagements. The guns were fitted with Magslip electrical data transfer from Predictors AA Nos 3, 5 and 10 and were probably used initially with GL radars and UB 10 18 feet base optical height and range finders. AA control radars evolved rapidly. The gun was laid and fuzes set by pointer matching, it is unclear the extent to which advances in 3.7-inch fire control were applied to 4.5-inch. During the war Machine Fuze Setter No 10 was added, This improved the rate of fire from 8 to 10 rounds per minute and raised the effective ceiling to 34,500 feet. Gun positions were usually in the vicinity of naval bases where they could use the naval ammunition supply. Initially the