Vickers manufactured these guns for the Brazilian river monitors Javary, Solimões and Madeira which were being built at Barrow. When it came time for delivery in 1914, the deal fell through as the Brazilians could no longer afford to pay for them. The ships were then laid up at the Devonshire Dock at Barrow until just prior to the start of World War I. At that time, First Sea Lord Winston Churchill expressed concern that these ships could be bought by an unfriendly power. As a result, the Royal Navy quickly purchased them in August 1914, renaming them Humber, Mersey and Severn.

These guns were generally identical, but were designed for use in twin turrets, with the Mark IV being the right-hand gun and the Mark XV being the left-hand gun.

As there were no spares, when these guns on Severn and Mersey wore out in October 1914 after extensive use off the Belgian coast, the turrets were removed and replaced with two single 6" (15.2 cm) BL Mark VII. Two of these guns had been salvaged from the pre-dreadnought HMS Montagu, which had been wrecked on Lundy Island in 1906. As Humber's guns were not so badly worn, she kept her turret.

During a bombardment of the Turkish village of Biyuk Anafarta on 9 June 1915, Humber suffered a bore premature in her right gun after 15 rounds. She remained in action with her other armament for a few more months until she was sent to Alexandria where both 6" (15.2 cm) guns were replaced by relined ones originally used on the other monitors.

Construction was similar to other Vickers wire guns of that time with cannelured rings at the forward inner A/A tube shoulders. Used a hand-worked Welin breech-block. A total of four guns of each Mark were built. The two spare guns, which for some reason were never used, differed in having tapered inner A tubes.

Gun Characteristics

Designation 6"/50 (15.2 cm) BL Mark XIV and XV
Ship Class Used On Severn class Monitors
Date Of Design 1912
Date In Service 1914
Gun Weight 8.094 tons (8.2 mt)
Gun Length oa 309.728 in (7.867 m)
Bore Length 300.0 in (7.620 m)
Rifling Length 265.2 in (6.736 m)
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 1,650 in3 (27.04 dm3)
Rate Of Fire 6 rounds per minute 1
  • ^

    The Rate of Fire figure given above is from "Big Gun Monitors," but "Warrior to Dreadnought: Warship Development 1860-1905" quotes Jellicoe's 1906 figures for rates of fire for guns of this caliber 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


Type Bag
Projectile Types and Weights 1a 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 28.63 lbs. (13.0 kg) MD26
Muzzle Velocity 2,900 fps (884 mps)
Working Pressure N/A
Approximate Barrel Life about 1,000 rounds
Ammunition stowage per gun 150 rounds 2a
  • ^Shells were 4crh.
  • ^Outfit was 50 rounds CPC and 100 rounds HE per gun.


Range with 100 lbs. (45.36) CPC
Elevation Distance
15 degrees 14,130 yards (12,920 m)

Armor Penetration

Armor Penetration with 100 lbs. (45.36 kg) CPC
Range KC Side Armor
7,500 yards (6,860 m) 3.5 in (89 mm)

Data from "Big Gun Monitors."

Mount/Turret Data

  • Twin Turret
    • Severn (1): Vickers Special Twin Turret
Weight 100 tons (102 mt)
Elevation -5 / +15 degrees
Elevation Rate Manual operation, only
Train about -150 / +150 degrees
Train Rate Manual operation, only
Gun recoil N/A

These mountings were an improved version of the twin turret used in the Monmouth class cruisers. No mark number was ever assigned.


Data from:

  • "Warrior to Dreadnought: Warship Development 1860-1905" by D.K. Brown
  • "Big Gun Monitors: The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
  • "British Naval Guns 1880-1945 No 12" article by John Campbell in "Warship Volume VIII"

Page History

07 January 2007
20 February 2009
Added details about bore premature