Comments by "COL BEAUSABRE" (@colbeausabre8842) on "HMS Charybdis - Guide 211" video.
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The 5.25's that were mounted as coast defense/anti aircraft guns, like all other heavy flak in British service (3, 3.7 and 4.5 inch) belonged to the Army, not the RAF.
"In early 1942 the Governor of Gibraltar sought 5.25-in guns for dual anti-aircraft/coast defence role. None was forthcoming. However, later that year Anti-Aircraft Command in UK acquired three twin-gun turrets from the Admiralty, which were installed around London in permanent positions.
https://en.wikipedia.org/wiki/QF_5.25-inch_naval_gun#/media/File:Twin_5.25_inch_AA_guns_Primrose_Hill_1943_IWM_H_032322.jpg
Trials and use led the army to design a single gun mounting in two marks, both with an underground engine room to provide electrical and hydraulic power for traverse, elevation, fuze setting, ramming and other tasks. Fitted with the standard army Machine Fuze Setter No 10, these guns had a rate of fire of 10 rds/min and a maximum height of 50,000 ft, with an effective height of 36,000 ft.[18] Mark 1A was a mild steel turret for anti-aircraft use only, Mk 1B was an armoured turret for anti aircraft and coast defence use.
https://en.wikipedia.org/wiki/QF_5.25-inch_naval_gun#/media/File:5.25_inch_gun_Port_Moresby_1944_AWM_075214.jpeg
The gun was designated Mk 2.
By the end of 1943 only 16 of the new guns had been installed, far below projections. By the end of the war 164 guns had been produced. The high-explosive shells were fuzed with the standard army No 208 mechanical time fuze, used with 3.7 and 4.5-inch anti-aircraft guns. The guns remained in service after World War II, and in 1953 11 guns were installed in Gibraltar"
https://en.wikipedia.org/wiki/QF_5.25-inch_naval_gun#/media/File:5.25-inch_BL_Dual_Purpose_Gun.jpg
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@Ushio01 Unquestionably Atlanta. The 5.25 inch mounts were notoriously crowded which meant they did not achieve in practice their theoretical ROF 0f 12 rpm, but instead were limited to 7-8 rpm. From the NAVWEAPS site " Unfortunately, the original design of the gunhouse was cramped and the heavy projectile and cartridge cases resulted in a lower rate of fire than expected. In addition, the slow elevating and training speeds of the mounts were found to be inadequate for engaging modern high-speed aircraft."
"As designed, the expected rate of fire for these guns was 10 - 12 rpm. However, the heavy weight of the projectile and cartridge case plus the semi-automated fuze setting mechanism meant that this round required much crew handling before it could be rammed into the breach. The tight design of the gunhouse also interfered with the smooth crew operation necessary to achieve high rates of fire. In the chapter regarding the design of the King George V class, "British Battleships of World War Two" states that: "The mounting was designed for a rate of fire of ten to twelve rounds per minute, but, in fact, the crews could not transfer shell and cordite from the hoists to the loading-trays at this speed, and the more usual rate of fire was seven to eight rounds per minute." This would imply that cruisers would have a similar rate of fire, as the layout of their gunhouse and movement of ammunition was essentially the same as for the battleship mounting.
The 5-38 inch had a theoretical rate of fire of 12 rounds/minute, but well drilled crews are routinely recorded as achieving up to 20 rpm. The AA cruiser HMS Delhi was unique in being rearmed with five 5-38's "the gunnery officer on Delhi reported that during gunnery trials in February and March 1942 that these guns were able to fire 25 rounds per minute with the ready-use ammunition stored in the handling rooms and 15 rounds per minute with the normal supply from the magazines.
So we're talking
Dido class = 5 turrets X 2 guns/turret X 8 rounds per gun = 80 rpm X 80 lbs/shell = 6400 lbs/minute
Oakland subclass (better apples to apples than the Atlantas) = 6 turrets X 2 guns/turret X 20 rounds/gun = 240 rpm (even at 12 rpm, it's 144 rpm) X 54 lbs/shell = 12,960 lbs/minute
An Atlanta would tear a Dido apart. It's only hope would be to stay out of range (24,000 vs 17,000 yards, No wonder the IJN talked about the "American 5 inch machine gun"
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