| Ordnance BL 8 inch gun Mk VIII | |
|---|---|
 Forward 8-inch turrets aboard HMAS Canberra | |
| Type | Naval gun Coast defence gun |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1927 – 1954[1] |
| Used by | Royal Navy Royal Australian Navy Spanish Navy |
| Wars | Second World War Spanish Civil War |
| Production history | |
| No. built | 168[2] |
| Specifications | |
| Mass | 17.5 tonnes[2] |
| Barrel length | 400 inches/10 meters(50 calibres)[2] |
| Shell | 256 pounds (116 kg) |
| Calibre | 8-inch (203 mm)[2] |
| Muzzle velocity | 2805 feet per second (855 m/s)[2] |
| Maximum firing range | 28 kilometres (17 mi)[2] |
The BL 8 inch gun Mark VIII[note 1] was the main battery gun used on the Royal Navy's County-class cruisers,[note 2] 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.[3] 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.[4]
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