The BL 8 inch gun Mark VIII was the main battery gun used on the Royal Navy's County-class 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 8 inches (203 mm) 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 Canarias-class 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 15 kg (33 lb) of cordite were used to fire a 116 kg (256 lb) 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 Exeter. 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.
County-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
== Shell trajectory == Range with 256 lbs. (116.1) SAPC with MV = 2,725 fps (831 mps)
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 == Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4. Lenton, H.T. & Colledge, J.J. (1968). British and Dominion Warships of World War Two. Doubleday and Company. Whitley, M.J. (1995). Cruisers of World War Two. Brockhampton Press. ISBN 1-86019-8740.
External links
Tony DiGiulian, Britain 8"/50 (20.3 cm) Mark VIII Terry Gander, Twentieth century British coast defence guns
