BL 6-inch Mk XII naval gun

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BL 6-inch Mk XII naval gun
HMS Warspite 6 inch gun casemate closeup.jpg
Casemate gun on HMS Warspite after the Battle of Jutland, June 1916
TypeNaval gun
Place of originUnited Kingdom
Service history
In service1914–2011
Used byBritish Empire
Production history
No. built463
Mass15,512 pounds (7,036 kg) barrel & breech[1]
Barrel length270 inches (6.858 m) bore (45 cal)[2]

Shell100 pounds (45.36 kg) Lyddite, Armour-piercing, Shrapnel[3]
Calibre6 inches (152.4 mm)
BreechWelin interrupted screw
RecoilHydro-spring, 16.5 inches (420 mm)[4]
Rate of fire5-7 rpm
Muzzle velocity2,825 feet per second (861 m/s)[6]
Maximum firing range19,660 metres (21,500 yd)[7]

The BL 6-inch Mark XII naval gun[8] was a British 45 calibre 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.


BL 6 inch Mk XII gun barrel diagram.jpg

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[edit]

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It superseded the 45-calibres Mk VII gun and the longer 50-calibres Mk XI gun which had proved unwieldy in light cruisers due to its length, and was Britain's most modern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

It was superseded as secondary armament on new battleships in the 1920s by the 50-calibre 6-inch Mk XXII gun, and as main armament on new light cruisers in the 1930s by the 50-calibre 6-inch Mk XXIII gun.

Guns were mounted in the following ships :

Coast defence gun[edit]

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

Notable actions[edit]


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 CRH shells for this gun.[1]

See also[edit]

Weapons of comparable role, performance and era[edit]

Surviving examples[edit]

Notes and references[edit]

  1. ^ a b 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[edit]