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.
Actual bore diameter of all British 4.7" guns was 4.724" (12 cm).
A Note on Sources: Buxton states 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. However, Friedman states that they were designated as 4.7in Howitzer Mk I.
| 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 | 88.9 in (2.258 m) |
| Bore Length | 85.0 in (2.160 m) |
| Rifling Length | 72.17 in (1.833 m) |
| Grooves | (36) |
| Lands | N/A |
| Twist | 1 in 40 12.17 in (30.9 cm) from muzzle then 1 in 20 |
| Chamber Volume | 180 in3 (2.95 dm3 |
| Rate Of Fire | about 10 rounds per minute |
| Type | As designed: Fixed
In Service: Separate |
|---|---|
| Projectile Types and Weights 1 | HE: 45 lbs. (20.4 kg) 2 |
| Bursting Charge | 10.625 lbs. (4.81 kg) |
| Projectile Length | N/A |
| Propellant Charge | 1.78 lbs. (0.81 kg) MD 4 1/4 3 |
| Muzzle Velocity | 1,200 fps (366 mps) 3 |
| Working Pressure | N/A |
| Approximate Barrel Life | N/A |
| Ammunition stowage per gun | 150 rounds |
- ^Ammunition was 2crh and only HE rounds were supplied.
- ^Originally this gun fired special fixed ammunition, but when taken over by the British, the DNO called for a new design that would use standard 4.7 in (12 cm) shells. The original casings were then cut down to 9.8 in (25 cm) in length and closed with a glazeboard top.
| Elevation | Distance |
|---|---|
| 45 degrees | 9,000 yards (8,230 m) |
| 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.
"Big Gun Monitors: The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"Naval Weapons of World War One" by Norman Friedman
21 February 2009 - New datapage
18 September 2025 - Converted to HTML 5 format, added gun and ammunition details and redid photograph