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BL 15 inch Mark I
HMS Terror 15 inch guns 1915 IWM SP 1612.jpg
As mounted on monitor HMS Terror, 1915.
Type naval gun
Place of origin UK
Service history
In service 1915-1959
Used by UK
Production history
Designed 1912
Manufacturer see text
Produced 1912-1918
Number built 186
Weight 100 long tons (100 t)[1]
Length 650.4 inches (16.52 m)[1]

Shell separate charges and shell
Shell weight 1,938 pounds (879 kg)
Calibre 15-inch (381.0 mm)
Recoil 46 inches (1.2 m)[1]
Rate of fire 2 rounds per minute
Muzzle velocity 2,458 feet per second (749 m/s)
Maximum range 33,550 yards (30,680 m) (Mk XVIIB or Mk XXII streamlined shell @ 30°)[2]

The BL 15 inch Mark I succeeded the 13.5-inch (340 mm) 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 efficient heavy gun ever developed by the Royal Navy. It was deployed on capital ships from 1915 until 1959, and was a key Royal Navy gun in both World Wars.


This gun was an enlarged version of the successful BL 13.5 inch Mk V naval gun, specifically intended to arm the new Queen Elizabeth-class battleships 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. The normal slow and cautious prototype and testing stages of a new gun's development were bypassed, and it was ordered straight from the drawing board due to the urgency of the times. In the event it met all expectations and was a competitive battleship main armament throughout both World Wars.

Diagram showing gun barrel construction

The barrel was 42 calibres long (i.e., 15 in x 42 = 630 in) and was referred to as "15 inch/42". This wire-wound gun fired a 1938 lb (879 kg) Mk XVIIB shell at a muzzle velocity of 2,458 ft/s (785 m/s).[2] Maximum range in shipboard mountings was 33,550 yards (30,680 m) (30 degrees elevation).[2] During World War II older battleships with gun elevation limited to 20 degrees 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 range to 37,870 yards (34,630 m) while using supercharges at a gun elevation of 30 degrees.[2] Coastal artillery mountings with higher elevations could reach 44,150 yards (40,370 m). 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.[3]



These guns were used on several classes of battleships from 1915 until HMS Vanguard, the last battleship to be built for the Royal Navy, completed in 1946.

Warships with the BL 15 inch Mark I gun:

Coastal batteries

  • Two coastal guns ("Clem" and "Jane") were mounted near Wanstone Farm in Kent in the 1940s.
  • Five guns were mounted in Singapore at Johore battery and Buona Vista Battery in the 1930s.
  • In the late 1920's Spain purchased four guns in single turrets to guard Cartagena. These are still in place and the two batteries they form part of, are being renovated, and open to the public.

Animation representing the loading cycle of the Mark I turret for the BL 15 inch Mark I.

Aft guns of HMS Hood trained forward to port, 1926

One of Singapore's 15 inch coastal defence guns elevated for firing


Two 15-inch guns outside the Imperial War Museum; the nearer gun from HMS Ramillies, the other from HMS Roberts.

186 guns were manufactured between 1912 and 1918.[4] They were removed from ships, refurbished, and rotated back into other ships over their lifetime.

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

World War II ammunition

Unexploded shell in the cathedral in Genoa (Italy).jpg
WW2 Singapore 15inch shell.jpg
108 lb Cordite cartridge ¼ charge
AP shell Mk XXII BNT
AP shell and cap, as fired by HMS Malaya into Genoa on 9 February 1941
An AP shell in the process of being hoisted to the gun breech, Singapore 1940

See also

Weapons of comparable role, performance and era


  1. 1.0 1.1 1.2 Ian Buxton, p. 181.
  2. 2.0 2.1 2.2 2.3 John Campbell, p. 25.
  3. Roskill, p. 89.
  4. Ian Buxton, p. 179.


  • Buxton, Ian Lyon (1978). Big Gun Monitors. Tynemouth: World Ship Society. ISBN 0-905617-06-1. 
  • Campbell, John (1985). Naval Weapons of World War II. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-459-4. 
  • Roskill, Captain Stephen Wentworth (1974). H.M.S. Warspite: The Story of a Famous Battleship. London: Futura Publications. ISBN 0-86007-172-3. 

External links

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