BL 12 inch Mk XI – XII naval gun

BL 12 inch gun Mk XI, Mk XII

Aft Mk XI guns of HMS Vanguard
Type Naval gun
Place of origin United Kingdom
Service history
In service 1910–1920
Wars World War I
Production history
Designer Vickers

Vickers Armstrong Whitworth Coventry Ordnance Works

William Beardmore
Barrel length 50 ft (15.24 m) bore (50 calibers)

Shell 850 lb (385.6 kg) Lyddite, Armour-piercing, Shrapnel[1]
Calibre 12 inches (304.8 mm)
Muzzle velocity 2,825 ft/s (861 m/s)[2]
Maximum firing range 19,380 m (21,190 yd)[3]

The BL 12 inch Gun Mark XI and Mark XII[note 1] were British breech loading (BL) naval guns of 50-calibres length mounted as primary armament on dreadnought battleships from 1910.


Vice-Admiral Doveton Sturdee in front of the Mk XII guns of a wing turret on HMS Hercules

In an effort to increase the armour-piercing capability and range of a 12 inch gun, the 50 calibres/600 inches Mk XI's barrel was 5 calibres/60 inches longer than the previous Mk X gun's 45 calibres. As a result, muzzle velocity increased from 2,700 feet per second (820 m/s) to 2,825 feet per second (861 m/s), but bore erosion, which led to short barrel life, and poor accuracy due to inconsistent cordite propellant burning, hampered the gun. The Mk XII derived from it suffered from the same problems.

Instead of attempting to improve their 12-inch gun, the British developed the 13.5-inch Mk V gun of 45-calibres, which could achieve greater range at lower muzzle velocities due to its larger shell.

Mk XI guns were mounted on:

Mk XII guns were mounted on:

See also

Weapons of comparable role, performance and era


  1. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. These were the eleventh and twelfth models of BL 12-inch guns.


  1. 850 lb shells : Treatise on Ammunition, 1915
  2. 2825 ft/second with 4 C.R.H. 850 lb projectile : As quoted in Range Tables for His Majesty's Fleet, Vol. I., 1918 9.2-Inch Guns and Above April, 1918 2825 ft/second using 307 lb cordite MD size 45 propellant : Treatise on Ammunition, 1915


External links

Media related to BL 12 inch Mk XI – XII naval gun at Wikimedia Commons

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