These guns were an Elswick design generally similar to the Mark XI and developed for the Brazilian battleship Rio de Janeiro. That ship was taken over by the British and renamed HMS Agincourt at the start of World War I. After she was scrapped, these guns were then reused in the gunboats HMS Aphis and HMS Ladybird in 1939. Some guns were used in emergency coast defense batteries during World War II.

Constructed of inner A tube, A tube and breech piece joined by a securing collar, wire, B tube, jacket, breech ring and breeech bush. Spare guns differed in having a B tube and jacket rather than a full-length jacket. Used a hand-worked Welin breech-block. A total of 24 guns were built.

Gun Characteristics

Designation 6"/50 (15.2 cm) BL Mark XIII
Ship Class Used On HMS Agincourt
HMS Aphis and HMS Ladybird in 1939
Date Of Design 1912
Date In Service 1914
Gun Weight 19,660 lbs. (8,918 kg)
Gun Length oa 310.4in (7.867 m)
Bore Length 300.0 in (7.620 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 1,550 in3 (25.40 dm3)
Rate Of Fire 5 - 7 rounds per minute 12
  • ^

    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 almost all British capital ships had few or slow hoists for their 6" (15.2 cm) guns and that once the ready ammunition was used up, the rate of fire dropped to about 3 rounds per minute.


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 24.6 lbs. (11.2 kg) MD26
24.4 lbs. (11.1 kg) SC140
Muzzle Velocity 2,770 fps (844 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun about 150 rounds


Range with 100 lbs. (45.36 kg) CPC
Elevation Distance
15 degrees 13,475 yards (12,320 m)

Mount/Turret Data

  • Single Mount
    • Agincourt (20) 1a: PXI
Weight N/A
Elevation Originally -7 / +13 degrees
Later -7 / +15 degrees and then to -7 / +20 degrees
Elevation Rate Manual operation, only
Train about -80 / +80 degrees
Train Rate Manual operation, only
Gun recoil N/A
  • ^Two guns were removed in 1918.


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
  • "The Big Battleship" by Richard Hough
  • "British Battleships: 1860 - 1950" by Oscar Parkes
  • "A Concentrated Effort: Royal Navy Gunnery Exercises at the End of the Great War" article by William Schleihauf in "Warship International" No. 2, 1998

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