BL 6 inch Mk XII naval gun

BL 6 inch gun Mk XII

Forward gun on cruiser HMS Galatea, February 1917
Type Naval gun
Place of origin United Kingdom
Service history
In service 1914 - 1945
Used by British Empire
Wars World War I
World War II
Production history
Designer Vickers
Designed 1913
Manufacturer Vickers
Number built 463
Weight 15,512 pounds (7,036 kg) barrel & breech[1]
Barrel length 270 inches (6.858 m) bore (45 cal)[2]

Shell 100 pounds (45.36 kg) Lyddite, Armour-piercing, Shrapnel[3]
Calibre 6 inches (152.4 mm)
Breech Welin interrupted screw
Recoil Hydro-spring, 16.5 inches (420 mm)[4]
Elevation -7° - 30°[5]
Muzzle velocity 2,825 feet per second (861 m/s)[6]
Maximum firing range 19,660 metres (21,500 yd)[7]

The BL 6 inch Gun Mark XII[8] was a British 45 calibres naval gun which was mounted as primary armament on light cruisers and secondary armament on dreadnought battleships commissioned in the period 1914 - 1926, and remained in service on many warships until the end of World War II.


This was a high-velocity naval gun consisting of inner "A" tube, "A" tube, wound with successive layers of steel wire, with a jacket over the wire.[9]

Naval service

Single gun on CP mounting on cruiser HMS Enterprise
Experimental twin turret on HMS Enterprise, seen in 1936, which formed the prototype for twin 6-inch turrets for the Nelson-class battleships, as well as the Leander and Arethusa-class cruisers
Gunners load a casemate gun on battleship HMS Malaya, May 1943. The men at left carry cordite cartridges, still in their storage cases, on their shoulders

It superseded the 45-calibres Mk VII gun and the longer 50-calibres Mk XI gun which had proved unwieldy in light cruisers due to its length, and was Britain's most modern 6-inch naval gun when World War I began.

Guns were mounted in the following ships :

Coast defence gun

During WWII some Mk XII guns were used in emergency coast defense batteries.[10]

Notable actions


This gun generated a higher pressure in the chamber on firing compared to preceding 6-inch guns such as Mk VII and Mk XI. This necessitated use of special shells capable of withstanding a pressure of 20 tons per square inch on firing, which had "Q" suffixed to the name. World War I shells were marked "A.Q." denoting special 4 C.R.H. shells for this gun.[1]

See also

Weapons of comparable role, performance and era

Surviving examples

Notes and references

  1. 1 2 Handbook, 1917, Page 5
  2. Handbook, 1917, Page 7
  3. 100 lb shells : Treatise on Ammunition, 1915
  4. Handbook, 1917, Page 6, 23-26
  5. 30° elevation was possible with P.XIII mountings used on light cruisers; 20° elevation was possible on some P.VII* mountings used on light cruisers; 14° elevation was possible with P.IX mountings used on battleships; 15° was possible with P.VII mountings used on light cruisers. Handbook, 1917, Pages 5, 31, 41, Plates 6, 24, 35
  6. 2,825 feet per second using 27 lb 2 oz cordite MD size 19 propellant was the figure used in range tables. New guns were quoted with a muzzle velocity of 2,845 feet per second. Handbook, 1917, Page 5
  7. "Gun Model: BR 6in 45cal BL Mk XII". navalhistory. Retrieved 6 September 2014.
  8. Mark XII = Mark 12 : Britain denoted Marks (models) of guns with Roman numerals until after World War II. This was the twelfth model of British BL 6-inch gun.
  9. Handbook, 1917, page 5, 6
  10. "Britain 6"/45 (15.2 cm) BL Mark XII and Mark XX". Retrieved 6 September 2014.


External links

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