BL 8 inch Mk VIII naval gun

The 50 calibre BL 8 inch gun Mark VIII was the main battery gun used on the Royal Navy's County-class heavy 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 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.

Country Name Origin Year
United Kingdom - UK (Great Britain) 1927
Country Name Operational Year Retirement Year
United Kingdom - UK (Great Britain) 1927 1954 View

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 : 14 ships
  • York-class heavy cruisers : 2 ships

Type Naval gun
Coast defence gun
Place of origin United Kingdom
Service history
In service 1927 - 1954
Used by  Royal Navy
 Royal Australian Navy
Wars Second World War
Production history
Number built 168
Weight 17.5 tonnes
Barrel length 400 inches (10 meters)
Shell 256 pounds (116 kg)
Calibre 8-inch (203 mm)
Muzzle velocity 2805 feet per second (855 m/s)
Maximum firing range 28 kilometres (17 mi)

End notes