BL 12-inch Mk VIII naval gun

The BL 12-inch Mark VIII naval gun[note 1] was one of the first large British rifled breech-loading naval guns designed for the higher pressures generated by the new cordite propellant of the 1890s, and Britain's first large wire-wound gun. It represented a major advance compared to previous British guns.

Ordnance BL 12-inch Mk VIII gun
Muzzle of gun on HMS Canopus, 1916
TypeNaval Gun, Coastal Defence
Place of originUnited Kingdom
Service history
In service1895–1927
Used byRoyal Navy
WarsWorld War I
Production history
DesignerWoolwich Arsenal
VariantsMk VIII, VIIIe, VIIIv[1]
Mass46 tons barrel & breech[2]
Barrel length35 ft 5 in (10.80 m) (35.43 calibres)[2]

Shell850 lb (390 kg)[2]
Calibre12-inch (304.8 mm)
Muzzle velocity2,367 ft/s (721 m/s)[3]
Effective firing range10,000 yd (9,100 m)[2]

The gun was installed on the Majestic-class battleships from 1895 and on the Canopus-class battleships from 1899. During World War I guns removed from the obsolete Majestic class were mounted in Lord Clive-class monitors for shore bombardment.

Land service

From 1921 to 1926 two guns from the decommissioned battleship HMS Illustrious were in service in the Tyne Turrets for coast defence, north and south of the mouth of the River Tyne in the northeast of England.

Problems in service

During bombardment service when mounted in the Lord Clive-class monitors deposition of copper from the projectile driving bands needed frequent removal. However, problems with the inner liners were more serious. The continual drag of the driving bands caused the liner to be gradually stretched forward. The resulting protrusion at the muzzle could simply be cut off, but in addition the liner began to form a ridge in the barrel near the shoulders of the outer ‘A’ tube, where the inner ‘A’ tube was keyed to the outer. The ridge accumulated copper from the driving bands, which could give sufficient retardation to the projectile to start the fuze, which resulted in a premature detonation either within the bore, or soon after leaving the muzzle. This happened several times during bombardment service, including an occasion when Lord Clive showered pieces of shell over the French destroyer Aventurier. The ‘steel choke’ restriction could be temporarily removed by rubbing down with an emery-covered block pulled back and forth in the bore, but the only permanent cure was to fit new guns with a modified design of liner, which had a different arrangement of internal shoulders.[4]


See also

Weapons of comparable role, performance and era


  1. Mark VIII = Mark 8. Britain used Roman numerals to denote marks (models, abbreviated Mk) of ordnance until after World War II. Hence this was the 8th model of British 12-inch breech-loading naval guns,


  1. Mk VIII was the original Naval design; Mk VIIIe and VIIIv were reserve guns manufactured in 1906 by Elswick Ordnance and Vickers respectively. Hogg & Thurston 1972, page 190. These incorporated changes to correct a steel choke problem (DiGiulian)
  2. Text Book of Gunnery 1902, Table XII Page 336
  3. 850 lb shell, with 174 lb cordite propellant. Text Book of Gunnery 1902, Table XII page 336
  4. Buxton, Ian (2008). Big Gun Monitors: Design, Construction and Operations, 1914–1945 (2 ed.). Seaforth Publishing, Pen and Sword Books Ltd, Sth Yorkshire S70 2AS, Great Britain. p. 224. ISBN 978-1-59114-045-0.


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