The BL 15-inch Mark I succeeded the BL 13.5-inch Mk V naval gun. It was the first British 15-inch (381 mm) gun design and the most widely used and longest lasting of any British designs, and arguably the most successful heavy gun ever developed by the

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...

. It was deployed on capital ships from 1915 until 1959 and was a key Royal Navy gun in both World Wars.

Design

Gun

This gun was an enlarged version of the successful BL 13.5-inch Mk V naval gun. It was specifically intended to arm the new s as part of the British response to the new generation of Dreadnought battleships Germany was building, during the naval arms race leading up to World War I. Due to the urgency of the times, the normally slow and cautious prototype and testing stages of a new gun's development were bypassed, and it was ordered straight from the drawing board. Despite its hurried development process, the gun met all expectations and was a competitive battleship main armament throughout both World Wars. According to an American report produced after World War II, the British 15 inch Mk I was the most reliable and accurate battleship main armament of the war, though other guns and mountings had superior individual features. Animated gun turret

The barrel was 42 calibres long (i.e., length of bore was 15 in x 42 = 630 in) and was referred to as "15 inch/42". Overall length of gun: 650.4 inches, Weight of gun, excluding breech mechanism: 97 tons 3cwt. Weight of breech mechanism: 2 tons 17cwt. Rifling: polygroove, 76 grooves, uniform right-hand twist of one turn in 30 calibres. This wire-wound gun fired at a muzzle velocity of 2,450 ft/s (749 m/s) (4 crh shell), 2,640 ft/s (6 crh shell) with supercharge. Weight of shell: 1,920 lbs (4 AP crh shell), 1,938 lbs (6 crh AP shell – 1937). Weight of charge: 428 lbs cordite, 490 lbs cordite for supercharge. The firing life of a 15-inch gun was approximately 335 full charge firings using standard charges, after which it had to be re-lined.Roskill, p. 89.

Mounting

All shipboard mounts of the gun were in twin turrets. Excepting on the battlecruiser , all mountings were designated Mk I, with an as-built maximum elevation of 20°, though some were subject to later modifications. HMS ''Hood'' had its guns in a unique mounting, designated Mk II. Incorporating experience from the Battle of Jutland, the Mk II mounting had a maximum elevation of 30°, thus increasing the maximum range. In the 1930s a modification of the Mk I mounting, designated the Mk I (N), was introduced for use in those capital ships that were completely reconstructed. The Mk I (N) mounting also increased the maximum elevation from 20° to 30°. Maximum range in shipboard mountings was 33,550 yards (30,680 m) (30° elevation). During World War II unreconstructed older battleships, with gun elevation limited to 20°, were supplied with supercharges to increase their maximum range to 29,930 yards (27,370 m) at 2638 ft/s (804 m/s) using the Mk XVIIB or Mk XXII projectile, while HMS ''Vanguard'' could theoretically range to 37,870 yards (34,630 m) while using supercharges at a gun elevation of 30°. Coastal artillery mountings with higher elevations could reach 44,150 yards (40,370 m). The Mk I mounting had a revolving weight of 750 tons (1915) and 785 tons (1935). The Mk I (N) had a revolving weight of 815 tons; the Mk I (N) RP12 mounts of HMS ''Vanguard'' had a revolving weight of 855 tons. The Mk II mounts of HMS ''Hood'' had a revolving weight of 860 tons.

In service employment

In battle

The BL 15-inch Mark I gun proved its effectiveness at the Battle of Jutland in 1916, scoring hits out to , a record for naval gunnery at that time. In World War II the gun was responsible for the longest range shell-hit ever scored by one battleship on another in combat. At the

Battle of Calabria The Battle of Calabria, known to the Italian Navy as the Battle of Punta Stilo, was a naval battle during the Battle of the Mediterranean in the Second World War. Ships of the Italian '' Regia Marina'' were opposed by vessels of the British R ...

on 9 July 1940, gained a hit on the Italian battleship with her first salvo at . In the Attack on Mers-el-Kébir, when the French fleet was largely neutralised following the fall of France to the Germans, the BL 15-inch Mark I gun (arming , and HMS ) was responsible for the destruction by a magazine explosion of the old battleship , and the disabling and beaching (deliberate running aground in shallow water) of the old battleship and the new battleship . ''Dunkerques main 225mm armour belt was twice penetrated by 15-inch shells, which destroyed its fighting and steaming abilities.

Warships

The Royal Navy during the Second World War A29851

These guns were used on several classes of battleships from 1914 until , the last battleship to be built for the

, completed in 1946. Warships armed with the BL 15-inch Mark I gun: * s (Five ships with eight guns each – 3 ships converted to Mk I (N)) * s (Five ships with eight guns each) * s (Two ships with six guns each – 1 ship converted to Mk I (N)) * – battlecruiser (Eight guns, Mk II mounting) * s (Two ships with four guns each) * s (Two ships with two guns each) * s (Two ships with two guns each) * s (Two ships with two guns each) * – battleship (Eight guns in mountings taken from ''Courageous'' and ''Glorious'' converted to Mk I (N), with additional armour, designated: Mk I (N) (RP12). The turret supports were designed to withstand supercharge firings.''Vanguard'' was unique among British battleships in having remote power control (RPC) for her main battery turrets.Raven and Roberts, p. 326

Coastal batteries

* Two coastal guns ("Clem" and "Jane") were mounted near Wanstone Farm in Kent in the 1940s, and were used extensively for cross-Channel fire throughout the war. * Five guns were mounted in

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at Johore battery and Buona Vista Battery in the 1930s.

Production

186 guns were manufactured between 1912 and 1918.Ian Buxton, p. 179. They were removed from ships, refurbished, and rotated back into other ships over their lifetime. *

Elswick Ordnance Company The Elswick Ordnance Company (sometimes referred to as Elswick Ordnance Works, but usually as "EOC") was a British armaments manufacturing company of the late 19th and early 20th century History Originally created in 1859 to separate William A ...

, Elswick,

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: 34 *

Armstrong Whitworth Sir W G Armstrong Whitworth & Co Ltd was a major British manufacturing company of the early years of the 20th century. With headquarters in Elswick, Newcastle upon Tyne, Armstrong Whitworth built armaments, ships, locomotives, automobiles and ...

, Openshaw,

Manchester Manchester () is a city in Greater Manchester, England. It had a population of 552,000 in 2021. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The t ...

: 12. * William Beardmore & Company,

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: 37 *

Coventry Ordnance Works Coventry Ordnance Works was a British manufacturer of heavy guns particularly naval artillery jointly owned by Cammell Laird & Co of Sheffield and Birkenhead, Fairfield Shipbuilding and Engineering Company of Govan, Glasgow and John Brown & Compa ...

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: 19 * Royal Gun Factory,

Woolwich Woolwich () is a district in southeast London, England, within the Royal Borough of Greenwich. The district's location on the River Thames led to its status as an important naval, military and industrial area; a role that was maintained thr ...

: 33 * Vickers, Son and Maxim,

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: 49 Two guns, one formerly from (left gun) and the other originally mounted in , but later moved to (right gun), are mounted outside the Imperial War Museum in London.

World War II ammunition

References

Bibliography

* * * *Jordan, John and Dumas, Robert (2009) ''French Battleships 1922–1956'', Seaforth Publishing, Barnsley. * *

External links

Information at Naval Weapons website

The IWM guns

Images from the Vickers Photographic Archives
* * Terry Gander
Twentieth century British coast defence guns
{{DEFAULTSORT:BL 15-inch Mk I naval gun Coastal artillery World War I naval weapons of the United Kingdom World War II naval weapons of the United Kingdom Naval guns of the United Kingdom 380 mm artillery