The 9.2 inch Railway Gun was first placed on a railway mounting in the First World War. Most were scrapped in the 1920’s but a few were retained, dismantled and put in to store. These were re-assembled in 1940 to provide a mobile, heavy reserve for the protection of the East and South coasts of England. Several were deployed between Dover and Canterbury in Kent.
The 9.2 inch Railway Guns were Mark 10 series similar to the Coast Defence Gun and the Mark 13 designed for railway mounting. The gun and loading platform were mounted on a revolving pedestal and four outriggers were provided to brace the truck against the shock of firing. A screw jack raised the bogie frames to relieve strain on the travelling springs.
The top carriage was a modified Vavasseur barbette carriage which recoiled up an inclined plane. Recoil was also controlled by two hydraulic buffers. The gun returned to the firing position under gravity.
Gun
| Mark 10RT | Converted Mk10 coast gun. Fitted with trunnion hoop & counterweight |
| Mark 10V RT | Mk 10V converted as above |
| Mark 10* RT | Mk 10* converted as above |
| Mark 13 | 35 calibre gun with trunnions set well back. Most weight at breech end. |
| Mark 13* | Wartime manufactured, probably few made |
| Mark 13 A | Similar to Mk 13* but with loose liner. Doubtful any made |
Data
Gun Mark 10, on Mounting Mark 3, on Truck Mark 2
| Weight of Gun & Breech Mechanism | 64,412 lbs |
| Total length | 442.35 inches |
| Length of bore | 429.33 inches (46.6 calibres) |
| Rifling | 46 grooves, uniform right hand 1/30 |
| Breech mechanism | Interrupted screw, percussion or electric fired |
| Elevation | 0° to +30° |
| Traverse | 360° |
| Recoil system | Vavasseur hydraulic buffer, gravity return. 34 inch stroke |
| Weight in action | 202,944 lbs |
Gun Mark 13, on Mounting Mark 4, on Truck Mark 2
| Weight of Gun & Breech Mechanism | 54,264 lbs |
| Total length | 335.025 inches |
| Length of bore | 322 inches (35 calibres) |
| Rifling | 46 grooves, uniform right hand 1/30 |
| Breech mechanism | Interrupted screw, percussion fired |
| Elevation | 0° to +40° |
| Traverse | 360° |
| Recoil system | Vavasseur hydraulic buffer, gravity return. 34 inch stroke |
| Weight in action | 194,824 lbs |
Performance
Firing standard 380 lb shell
Gun Mark 10, on Mounting Mark 3, on Truck Mark 2
| Muzzle Velocity | 2,700 feet/second |
| Maximum Range | 21,000 yards |
Gun Mark 13, on Mounting Mark 4, on Truck Mark 2
| Muzzle Velocity | 2,100 feet/second |
| Maximum Range | 22,600 yards |
Ammunition
| Shell, HE, Mark 19B | Nose fuzed. Used Fuze Percussion, No. 45P |
| Shell, APC, Mark 15B | Capped shell. Used Base Fuze Percussion, No. 346 |
| Shell, CPC Mark 9A | Capped shell. Used Base Fuze Percussion, No. 15 |
| Shell, Shrapnel, Mark 10A | Used up in practice & declared obsolete |
| Propelling Charge | 2 half charge bags bundled in a silk cloth bag with gunpowder igniter to rear. Two of these made up a full charge. |