Britain 6"/50 (15.2 cm) BL Mark XVII and Mark XXI

Britain
6"/50 (15.2 cm) BL Mark XVII
6"/50 (15.2 cm) BL Mark XXI
Updated 11 February 2012

The Mark XVII was another 6" (15.2 cm) gun designed for the foreign markets, this one for the Chilean battleships Almirante Latorre and Almirante Cochrane. The Almirante Latorre was almost completed in 1914 when World War I started, and shortly afterwards she was taken over by the British and renamed HMS Canada. The Almirante Cochrane lay half-completed until after the war when she was renamed HMS Eagle, converted to an aircraft carrier. At that time, she used these 6" (15.2 cm) guns as her main armament. HMS Canada was returned to Chile after the war and remained in service as Almirante Latorre until decommissioned in 1958 while HMS Eagle was sunk by Japanese aircraft in 1942.

Of built-up construction and wire wound, generally similar to the Mark 12. Used a hand-worked Welin breech-block. Used an Elswick sliding hinge mechanism, with the fore portion of the breech being conical. A total of 29 guns were made.

The Mark XXI was originally ordered by Chile as a coastal defense gun and was almost identical to the Mark XVII except for a longer chamber and B tube and jacket rather than a full length jacket. Sixteen guns were made of which ten were taken over by the British Army for coast defense.

The data that follows is for the Mark XVII except where specified.

HMS Eagle
The 6" (15.2 cm) guns are in the single mounts under the flight deck

6"/50 (15.2 cm) gun from Chilean battleship Latorre now at Museo de Cañones Navales in Bahia de Valparaíso, Chile
Photograph copyrighted by Carlos Mey and used here by his kind permission

Gun Characteristics .

Designation	6"/50 (15.2 cm) BL Mark XVII 6"/50 (15.2 cm) BL Mark XXI
Ship Class Used On	Mark XVII: Canada and Eagle Mark XXI: Coast defense batteries
Date Of Design	1913
Date In Service	1914
Gun Weight	19,524 lbs. (8,856 kg)
Gun Length oa	310.4 in (7.885 m)
Bore Length	300.0 in (7.620 m)
Rifling Length	N/A
Grooves	N/A
Lands	N/A
Twist	N/A
Chamber Volume	1,650 in³ (27.04 dm³)
Rate Of Fire (see Note)	5 - 7 rounds per minute
Note: The Rate of Fire figure given above is found in references for British guns of this caliber, but "Warrior to Dreadnought: Warship Development 1860-1905" quotes Jellicoe's 1906 figures for rates of fire for these guns in gunlayers' tests and in battle practice and notes that the latter figures corresponded well to those actually attained by the Japanese at Tsushima: Gunlayers Test: 12 rounds per minute Battle Practice: 4 rounds per minute In "Jutland: An Analysis of the Fighting" by John Campbell, it is stated that, unique among British capital ships, that Canada's hoists were capable of supplying about 5.5 rounds per minute.

Ammunition .

Type	Bag
Projectile Types and Weights	CPC 4crh - 100 lbs. (45.3 kg) HE 4crh - 100 lbs. (45.3 kg)
Bursting Charge	CPC - 7.5 lbs. (3.4 kg) HE - 13.3 lbs. (6.0 kg)
Projectile Length	CPC - 23.5 in (59.7 cm) HE - 22.9 in (58.2 cm)
Propellant Charge	28.6 lbs. (13.0 kg) MD26 28.1 lbs. (12.76 kg) SC140
Muzzle Velocity	2,905 fps (885 mps)
Working Pressure	N/A
Approximate Barrel Life	N/A
Ammunition stowage per gun	N/A

Range .

Elevation	With 100 lbs. (45.36) CPC Shell
Range @ 20 degrees	16,190 yards (14,800 m)

Mount / Turret Data .

Designation	Single Mounts Canada (16): PXII Eagle (9): PXII*
Weight	30,520 lbs. (13,844 kg) without shield
Elevation	PXII: -7 / +15 degrees PXII*: -7 / +20 degrees
Elevation Rate	Manual operation, only
Train	about +80 / -80 degrees
Train Rate	Manual operation, only
Gun recoil	N/A
Note: HMS Canada had two guns removed in 1916.

Data from
"Warrior to Dreadnought: Warship Development 1860-1905" by D.K. Brown
"Naval Weapons of World War Two" and "British Naval Guns 1880-1945 No 12" article in "Warship Volume VIII" both by John Campbell
"British Cruisers of World War Two" by Alan Raven and John Roberts
"A Concentrated Effort: Royal Navy Gunnery Exercises at the End of the Great War" article by William Schleihauf in "Warship International" No. 2, 1998

Page History

05 April 2008 - Benchmark
11 February 2012 - Updated to latest template