The QF 5.25 inch Mark I dual purpose gun has been dogged with controversy as well. The RN Gunnery Pocket Book published in 1945 states that: ""The maximum rate of fire should be 10–12 rounds per minute."". Wartime experience revealed that the maximum weight which the loading numbers could handle comfortably was much lower than 80–90 lb and the weight of the 5.25-inch ammunition caused serious difficulties, allowing them to manage only 7–8 rpm instead of the designed 10–12 rpm. The mount had a maximum elevation of +70 degrees and the slow elevating and training speeds of the mounts were inadequate for engaging modern high-speed aircraft. Despite this "Prince of Wales" was credited with several 5.25-inch kills during Operation Halberd and damaged 10 of 16 high level bombers in two formations during her last engagement, two of which crash landed. had her 5.25-inch turrets upgraded to RP10 control which increased training and elevating speeds to 20 degrees per second. These ships were equipped with the HACS AA fire control system and the Admiralty Fire Control clock for surface fire control of the secondary armament.