BL 14-inch Mk VII naval gun

The BL 14-inch Mk VII naval gun[2] was a breech loading (BL) gun designed for the battleships of the Royal Navy in the late 1930s. This gun armed the King George V-class battleships during the Second World War.

BL 14-inch Mark VII
Gunners and forward turrets of HMS Duke of York after the Battle of North Cape
TypeNaval gun
Place of originUK
Service history
In service1940-1951
Used byUK
Production history
No. built78
Mass80.26 metric tons (176,900 lb)
Barrel length53 ft 6 in (16.31 m) bore (45 calibres)

Shell1,590 lb (720 kg)
Calibre14 inches (355.6 mm)
ElevationNaval: 41°
Coastal: 45°
Rate of fire2 rounds per minute
Muzzle velocityStandard Charge: 2,483 ft/s (757 m/s) (new gun), 2,400 ft/s (730 m/s) (25% wear)[1]
Maximum firing range38,600 yd (35,300 m) at 40° with new linings, or 36,500 yd (33,400 m) at 40.7° (25% wear)


The choice of calibre was limited by the Second London Naval Treaty, an extension of the Washington Naval Treaty which set limits on the size armament and number of battleships constructed by the major powers. After disappointing experiences with the combination of high velocity but relatively light shell in the BL 16 inch /45 naval gun of the Nelson-class battleships, the British reverted to the combination of lower velocities and (relatively) heavier shells in this weapon.[3]



The built-up gun was of an all-steel construction, using a radial expansion design; this was an advance on earlier British heavy guns, which employed a wire-wound technology. The resulting gun was lighter, less prone to droop, more accurate and had a significantly longer barrel life. The estimated barrel life was 340 effective full charges. The new 14-inch Armour Piercing (AP) 1,590-pound shell had, relative to its size, superior ballistic performance and armour-penetration compared to previous British shells, due to improvements in design and material which had taken place since World War I.[4] The shell also carried a very large[5][6] bursting charge of 48.5 lb (22.0 kg)[7] Length of bore: 630 inches (45 calibres long). Weight of gun (without breech or counterbalance: 77 tons 14 cwt 84 lbs. Weight of gun with counterbalance: 89 tons 2 cwt 84 lbs. Weight of breech mechanism: 1 ton 17 cwt. Rifling: polygroove, 72 grooves plain section, uniform right-hand twist of 1 turn in 30 calibres. The standard propellant charge: 338 lb (153 kg) of cordite.[8]


The choice of mounting was a mechanically complex quadruple turret (each battleship had 2 quadruple turrets (Mark III) and one twin turret (Mark II)). Although the class of battleships was initially designed with 3 quadruple turrets, it proved impossible to include this amount of firepower and the desired level of protection without exceeding the 35,000 ton displacement treaty limit, furthermore the weight of the superimposed quadruple "B" turret brought the stability of the vessel into question, hence the "B" turret was changed to a smaller twin mount so the weight savings could be freed up for increased armour protection. The turret and ammunition-handling facilities incorporated many anti-flash measures and interlocks, improving safety but adding to complexity.[9] Revolving weight of mountings: quadruple Mk III 1,582 tons, twin Mk II 915 tons.[10]

In service, the quad turrets proved to be less reliable than was hoped for. Wartime haste in building, insufficient clearance between the rotating and fixed structure of the turret, insufficient full calibre firing exercises and extensive arrangements to prevent flash from reaching the magazines[11] led to problems during prolonged actions. In order to bring ammunition into the turret at any degree of train, the design included a transfer ring between the magazine and turret; this did not have sufficient clearance to allow for the ship bending and flexing.[12] These defects were addressed, and improved clearances, improved mechanical linkages, and better training led to greater reliability in the quadruple turrets but they remained controversial.[11]


On entering operational service the turrets gained an initial reputation for unreliability, with individual guns and entire turrets jamming in action. However, it has been argued that these jams were typically caused by errors in drill, either due to lack of gun crew training, as was the case when the newly commissioned HMS Prince of Wales engaged the Bismarck in the Battle of the Denmark Strait (1941), or due to crew fatigue resulting from the prolonged nature of the engagement, as was the case when HMS King George V engaged Bismarck in 1941 and HMS Duke of York engaged Scharnhorst in the Battle of North Cape (1943).[13]

During the battle against Bismarck a close-range hit from a 14-inch shell fired by King George V penetrated the 340 mm (13 in)-thick armour of the barbette of Bismarck's 'B' turret, causing an internal explosion which blew the rear face of the turret away. Underwater survey also shows that the 350 mm (14 in) vertical armour of the conning tower of Bismarck was penetrated by 14-inch shells.[14] In the Battle of North Cape, Duke of York fired 52 broadsides; of these 31 straddled the Scharnhorst, a fast and actively manoeuvring target, and a further 16 fell within 200 yards – an excellent performance, even when radar-control is taken into account.[15] The effects of the 14-inch shellfire on Scharnhorst quickly degraded her fighting abilities: Duke of York's first salvo put 'A' turret out of action; 'B' turret soon followed; a subsequent hit penetrated the German ship's armour, detonating in one of the boiler rooms and reducing the vessel's speed. This reduction in speed meant that the Scharnhorst could not escape pursuit, and was responsible for her eventual destruction.[16]

By being instrumental in the destruction of two modern enemy battleships, the 14-inch Mark VII gun was, arguably, one of the most successful battleship main armaments of World War II.[17]

Coastal guns

In World War II two guns, nicknamed Winnie and Pooh, were mounted as coastal artillery near Dover to engage German batteries across the Channel in occupied France.

Armour penetration

  • Penetration at a muzzle velocity of 2483 ft/s, guns with new linings or with no significant wear:
  • Belt
    • 729 mm (28.7 in) @ 0 m (0yd)
    • 531 mm (20.9 in) @ 9,144 m (10,000 yd)
    • 452 mm (17.8 in) @ 13,716 m (15,000 yd)
    • 389 mm (15.3 in) @ 18,288 m (20,000 yd)
  • Decks
    • 33 mm (1.3 in) @ 9,144 m (10,000 yd)
    • 51 mm (2.0 in) @ 13,716 m (15,000 yd)
    • 69 mm (2.7 in) @ 18,288 m (20,000 yd)
    • 89 mm (3.5 in) @ 22,860 m (25,000 yd)
    • 107 mm (4.2 in) @ 25,603 m (28,000 yd)

Reproduced from Nav

Surviving example

See also


  1. With 338.3 lb (153.5 kg) cordite.
  2. Mk VII = Mark 7. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. This was the seventh model of BL 14-inch naval gun.
  3. Raven and Roberts, p. 283
  4. Raven and Roberts, p. 285
  5. Naval Weapons index, The German KM 38 cm/52 SK C/34 (15-inch) carried a 41.4lb bursting charge, while the USN 16-inch Mk VI 2700 lb AP shell carried a 40.9lb bursting charge
  6. USN Bureau of Ordnance, Naval Ordnance 1937 Edition, paragraph 1318: "The impact damage which a projectile itself does is entirely secondary to that which results from its burst. The design of most naval projectiles is based primarily on using the projectile as a vehicle with which to carry a quantity of explosive into a ship and secondarily to provide missiles with which to carry the force of the explosion."
  7. Tony DiGiulian. "British 14"/45 (35.6 cm) Mark VII". NavWeaps.
  8. Raven and Roberts, p. 423
  9. Kaplan, p. 88
  10. Raven and Roberts, p. 423
  11. Garzke & Dulin, p. 228
  12. Brown Nelson to Vanguard (2006) p31
  13. Kaplan, p. 88
  14. Garzke, Dulin and Webb
  15. Burt, p. 390
  16. Raven and Roberts, p. 356
  17. Other battleship main armaments largely or wholly responsible for destroying battleships in WWII: the German 38 cm SK C/34 naval gun (15-inch) sank 1 battleship, HMS Hood; a combination of the American 16"/45 caliber gun and the 14"/50 caliber gun sank 1 battleship, Yamashiro; and the American 16"/45 caliber Mark 6 gun destroyed 1 battleship, Kirishima; the British BL 15-inch Mk I naval gun sank 1 battleship, Bretagne; the British BL 16 inch Mk I naval gun (combined with the BL 14-inch Mk VII naval gun) destroyed 1 battleship, the Bismarck. It is notable that the only modern battleships destroyed by battleship gunfire were the Bismarck and Scharnhorst, all the other battleships to suffer this fate were designs dating back to World War I, with various degrees of modernisation.


  • Brown, D K (2006). Nelson to Vanguard: Warship Design and Development 1923–1945. Chatham Publishing.
  • Burt, R. A. (2012). British Battleships, 1919–1939 (2nd ed.). Annapolis, Maryland: Naval Institute Press. ISBN 978-1-59114-052-8.
  • Garzke, William H., Jr.; Dulin, Robert O., Jr. (1980). British, Soviet, French, and Dutch Battleships of World War II. London: Jane's. ISBN 0-7106-0078-X.
  • Garzke, William H. Jr., Dulin, Robert O. Jr. and Webb, Thomas G. (1994) Bismarck's Final Battle, Warship International No. 2. Available as a web version at
  • Kaplan, P. (2014) World War Two at Sea: The Last Battleships, Pen and Sword Books, Barnsley. ISBN 147383628X
  • Raven, Alan; Roberts, John (1976). British Battleships of World War Two: The Development and Technical History of the Royal Navy's Battleship and Battlecruisers from 1911 to 1946. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-817-4.
  • Page from Nav
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