BL 8-inch Mk VIII naval gun
Introduction The '''BL 8 inch gun Mark VIII''' was the main battery gun used on the Royal Navy's  cruisers, in compliance with the Washington Naval Treaty of 1922.This treaty allowed ships of not more than 10,000 tons standard displacement and with guns no larger than  to be excluded from total tonnage limitations on a nation's capital ships. The 10,000 ton limit was a major factor in design decisions such as turrets and gun mountings. A similar gun formed the main battery of Spanish  cruisers. In 1930, the Royal Navy adopted the BL 6 inch Mk XXIII naval gun as the standard cruiser main battery in preference to this 8-inch gun.
Description These guns, 50 calibres long, were built-up guns which consisted of a wire-wound tube encased within a second tube and jacket with a Welin breech block and hydraulic or hand-operated Asbury mechanism. Two cloth bags each containing  of cordite were used to fire a  projectile. Mark I turrets allowed gun elevation to 70 degrees to fire high-explosive shells against aircraft. Hydraulic pumps proved incapable of providing sufficient train and elevation speed to follow contemporary aircraft; so simplified version of the Mark II turrets with a maximum elevation of 50 degrees were installed in the '. Each gun could fire approximately five rounds per minute. Useful life expectancy was 550 effective full charges (EFC) per barrel.
Naval service The following ships mounted Mk VIII guns in 188-tonne twin turrets. The standard main battery was four turrets, but ''Exeter'' and ''York'' carried only three to reduce weight and formed the separate ''York'' class. *  heavy cruisers : 13 ships** ''Canarias''-class heavy cruisers : 2 ships* ''York''-class heavy cruisers : 2 ships
Coast defence guns Six single guns capable of elevating to 70 degrees were installed as coastal artillery in the Folkestone-Dover area during the Second World War.
Ammunition File:BL8inchSAPKMkIBNTShell1943Diagram.jpg|File:BL8inchHENavalShellDiagram1934.jpg|File:428 Battery setting 8 inch shell fuzes WWII IWM TR 564.jpg|
Shell trajectory Range with 256 lbs. (116.1) SAPC with MV = 2,725 fps (831 mps)RangeElevationTime of flightDescentImpact velocity   2° 116 s2° 312154 ft/s (657 m/s)5° 1414 s7° 151683 ft/s (513 m/s)9° 4725 s15° 491322 ft/s (403 m/s)16° 3438 s28° 311169 ft/s (356 m/s)26° 4456 s43° 71164 ft/s (355 m/s)41° 2879 s56° 371240 ft/s (378 m/s)
See also ===Weapons of comparable role, performance and era===*203mm/50 Modèle 1924 gun French equivalent*20.3 cm SK C/34 Naval gun German equivalent*203 mm /53 Italian naval gun Italian equivalent*20 cm/50 3rd Year Type naval gun Japanese equivalent*8"/55 caliber gun US equivalent
Surviving examples * A gun from HMAS ''Australia'' outside the Australian War Memorial, Canberra
Notes
References
Bibliography * * *
External links * Tony DiGiulian,  Britain 8"/50 (20.3 cm) Mark VIII* Terry Gander,  Twentieth century British coast defence guns