BL 8-inch Mk VIII naval gun

The 50 calibre BL 8 inch gun Mark VIII[note 1] was the main battery gun used on the Royal Navy's County-class heavy 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]

Ordnance BL 8 inch gun Mk VIII
Forward 8-inch turrets aboard HMAS Canberra
TypeNaval gun
Coast defence gun
Place of originUnited Kingdom
Service history
In service1927 – 1954[1]
Used byRoyal Navy
Royal Australian Navy
Spanish Navy
WarsSecond World War
Spanish Civil War
Production history
No. built168[2]
Mass17.5 tonnes[2]
Barrel length400 inches/10 meters(50 calibres)[2]

Shell256 pounds (116 kg)
Calibre8-inch (203 mm)[2]
Muzzle velocity2805 feet per second (855 m/s)[2]
Maximum firing range28 kilometres (17 mi)[2]


These built-up guns 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 Mark II turrets with a maximum elevation of 50 degrees were installed in the Norfolk subgroup ships Dorsetshire and Norfolk and the York-class cruisers York and Exeter. Each gun could fire approximately five rounds per minute. Useful life expectancy was 550 effective full charges (EFC) per barrel.[2]

The following ships mounted Mk VIII guns in 188-tonne twin turrets.[2] The standard main battery was four turrets, but Exeter and York carried only three to reduce weight and formed the separate York class.[5]

  • County-class heavy cruisers : 14 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.[2]


Shell trajectory

Range[2] Elevation Time of flight Descent Impact velocity
5000 yd (4.6 km)  11 6 s  31 2154 ft/s (657 m/s)
10000 yd (9.1 km)  14 14 s  15 1683 ft/s (513 m/s)
15000 yd (14 km)  47 25 s 15° 49 1322 ft/s (403 m/s)
20000 yd (18 km) 16° 34 38 s 28° 31 1169 ft/s (356 m/s)
25000 yd (23 km) 26° 44 56 s 43° 7 1164 ft/s (355 m/s)
29000 yd (27 km) 41° 28 79 s 56° 37 1240 ft/s (378 m/s)

See also

Weapons of comparable role, performance and era

Surviving examples


  1. Mark VIII = Mark 8. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence this was the eighth model of BL 8-inch naval gun.
  2. A more accurate term is "Treaty Cruiser", as the term heavy cruiser was only formally defined at the time of the London Naval Treaty of 1930. However, all the 8-inch gun cruisers introduced as a result of the 1922 Washington Treaty were what became known as "heavy cruisers".


  1. Whitley 1995 pp.17,83&89
  2. Campbell 1985 pp.31–33
  3. Campbell 1985 p.389
  4. Whitley 1995 pp.96–127
  5. Lenton & Colledge 1968 pp. 36–39


  • 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.
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