Military Wiki
BL 6 inch gun Mk XI
Gunnery exercise on HMAS Melbourne circa. 1913
Type Naval gun
Coast defence gun
Place of origin  United Kingdom
Service history
In service 1906 - 1950s
Wars World War I World War II
Production history
Variants Mk XI
Barrel length 300 inches (7.620 m) bore (50 cal)

Shell 100 pounds (45.36 kg) Lyddite, Armour-piercing, Shrapnel[1]
Calibre 6 inches (152.4 mm)
Muzzle velocity 2,900 feet per second (884 m/s)[2]
Maximum range 18,000 yards (16,000 m) @ 22.5°[3]

The BL 6 inch Gun Mark XI[4] was a British 50 calibres high-velocity naval gun which was mounted as primary armament on cruisers and secondary armament on pre-dreadnought battleships.


The gun with its increased length of 50 calibres gave improved firepower over the current 6-inch Mk VII gun of 45 calibres. However, its increased length and weight made it unwieldy in the current manually operated shipboard mountings on light cruisers, which did not provide a steady platform. Britain reverted to 45-calibres guns in new warships from 1914 onwards with the BL 6 inch Mk XII gun.

Naval gun

Guns were mounted in the following ships :

Coast defence gun

Gun and crew at Fort Cowan, Brisbane, November 1943

The Mk XI gun was emplaced for coast defence in South Africa and particularly in Australia leading up to World War II, and remained in service until the 1950s. Guns in Australia came from the decommissioned World War I cruisers HMAS Sydney, HMAS Melbourne and HMAS Brisbane and were emplaced in northern Australia and Torres Strait to defend against possible attack by Japan,[5][6] and on Rottnest Island WA, Brisbane and the Sydney harbour[7] and Port Kembla[8] defences.

See also

Weapons of comparable role, performance and era

Surviving examples


  1. 100 lb shells : Treatise on Ammunition, 1915
  2. 2900 ft/second : As quoted in "Range Tables for His Majesty's Fleet, 1910. February, 1911"; with 32 lb 1½ oz cordite MD size 26 propellant : Treatise on Ammunition, 1915
  3. 18,000 yards @ 22.5° elevation as coast defence gun, quoted by Spethman, 2008. Guns in naval use had lower elevation and hence shorter range.
  4. Mk XI = Mark 11, i.e. the eleventh model of BL 6-inch guns. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II.
  5. Vanessa Seekee, "Artillery in Torres Strait 1891 - 1945: the silent forgotten sentinels of the north" in Memoirs of the Queensland Museum Cultural Heritage series, Volume 4 Part 1, November 2006
  6. For photograph of gun at Emery Point, Darwin 1934 see ID Number: P02024.026 at Australian War Memorial photo archive
  7. For photograph of gun at Signal Hill 1946 see ID Number: 129982 at Australian War Memorial photo archive
  8. See The Diary and Journal of General Sir John G. N. Wilton, Royal Australian Army 1910 - 1977


  • David Spethman, "The Garrison Guns of Australia 1788 - 1962", published by Ron H Mortensen, Inala QLD 2008. ISBN 978-0-9775990-8-0

External links

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