The BL 15-inch Mark I succeeded the

BL 13.5-inch Mk V naval gun The BL 13.5 inch Mk V gunMk V = Mark 5. Britain used Roman numerals to identify Marks (models) of ordnance until after World War II. This was the fifth model of British 13.5 inch gun was a British heavy naval gun, introduced in 1912 as th ...

. 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 F ...

. 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

. 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 A naval arms race is a situation in which two or more countries continuously construct warships that are consistently more powerful than warships built by the other country built in the previous years. These races often lead to high tension and near ...

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 Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately to i ...

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 Battle of Jutland (german: Skagerrakschlacht, the Battle of the Skagerrak) was a naval battle fought between Britain's Royal Navy Grand Fleet, under Admiral John Jellicoe, 1st Earl Jellicoe, Sir John Jellicoe, and the Imperial German Navy ...

, 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

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 World War II, Second World War. Ships of the Kingdom of Italy, Italian ''Regia Marina'' were oppose ...

on 9 July 1940, gained a hit on the Italian battleship with her first salvo at . In the

Attack on Mers-el-Kébir The Attack on Mers-el-Kébir (Battle of Mers-el-Kébir) on 3 July 1940, during the Second World War, was a British naval attack on neutral French Navy ships at the naval base at Mers El Kébir, near Oran, on the coast of French Algeria. The atta ...

, 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

Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...

at Johore battery and

Buona Vista Battery The Buona Vista Battery was the site of two 15" guns that were constructed during the late 1930s as part of the Singapore defenses. History From the mid through late 1930s, the western Singapore defenses were enhanced by the addition of two 15" ...

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,

Newcastle Newcastle usually refers to: *Newcastle upon Tyne, a city and metropolitan borough in Tyne and Wear, England *Newcastle-under-Lyme, a town in Staffordshire, England *Newcastle, New South Wales, a metropolitan area in Australia, named after Newcastle ...

: 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 a ...

Openshaw Openshaw is a suburb of Manchester, England, about three miles east of the city centre. Historically part of Lancashire, Openshaw was incorporated into the city of Manchester in 1890. Its name derives from the Old English ''Opinschawe'', which me ...

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 William Beardmore and Company was a British engineering and shipbuilding conglomerate based in Glasgow and the surrounding Clydeside area. It was active from 1886 to the mid-1930s and at its peak employed about 40,000 people. It was founded and ...

Parkhead Parkhead ( sco, Pairkheid) is a district in the East End of Glasgow. Its name comes from a small weaving hamlet at the meeting place of the Great Eastern Road (now the Gallowgate and Tollcross Road) and Westmuir Street. Glasgow's Eastern Necropo ...

Glasgow Glasgow ( ; sco, Glesca or ; gd, Glaschu ) is the most populous city in Scotland and the fourth-most populous city in the United Kingdom, as well as being the 27th largest city by population in Europe. In 2020, it had an estimated popul ...

: 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 ...

Coventry Coventry ( or ) is a City status in the United Kingdom, city in the West Midlands (county), West Midlands, England. It is on the River Sherbourne. Coventry has been a large settlement for centuries, although it was not founded and given its ...

: 19 *

Royal Gun Factory The Royal Arsenal, Woolwich is an establishment on the south bank of the River Thames in Woolwich in south-east London, England, that was used for the manufacture of armaments and ammunition, proofing, and explosives research for the British ...

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 throu ...

: 33 * Vickers, Son and Maxim,

Barrow-in-Furness Barrow-in-Furness is a port town in Cumbria, England. Historically in Lancashire, it was incorporated as a municipal borough in 1867 and merged with Dalton-in-Furness Urban District in 1974 to form the Borough of Barrow-in-Furness. In 2023 the ...

: 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 Imperial War Museums (IWM) is a British national museum organisation with branches at five locations in England, three of which are in London. Founded as the Imperial War Museum in 1917, the museum was intended to record the civil and military ...

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