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.

Interesting in that these guns were apparently never given an official Mark number, even though the 6" (15.2 cm) guns on these ships were given standard Mark designations.

Actual bore diameter of all British 4.7" guns was 4.724" (12 cm).

Gun Characteristics

Designation 4.7"/18 (12 cm) Howitzer
Ship Class Used On Severn class Monitors
Date Of Design 1912
Date In Service 1913 (taken over by the British in 1914)
Gun Weight 0.57 tons (0.58 mt) including breech mechanism
Gun Length oa 89.9 in (2.283 m)
Bore Length 85.0 in (2.160 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire about 10 rounds per minute


Type Fixed
Projectile Types and Weights 1 HE: 45 lbs. (20.4 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 1.78 lbs. (0.81 kg) MD
Muzzle Velocity 1,200 fps (366 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun 150 rounds
  • ^Ammunition was 2crh and only HE rounds were supplied.


Range with 45 lbs. (20.4 kg) HE
Elevation Distance
45 degrees 9,000 yards (8,230 m)

Mount/Turret Data

Designation Single open mounts: Severn (2)
Weight 4.65 tons (4.72 mt)
Elevation -5 / +70 degrees
Elevation Rate Manually operated, only
Train about +120 / -120 degrees
Train Rate Manually operated, only
Gun recoil N/A

Had simple shields.


Data from:

  • "Big Gun Monitors: The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton

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