10in Gun on Sliding Railway Mount
The 10in Gun on Sliding Railway Mount was produced using US guns on French railway mounts in an attempt to speed up production, but none were ready before the end of the First World War.
After the US entry into the war the Americans offered to provide fifteen 10in guns to France, and ordered 36 railway mounts for 10in guns, to be constructed in France and armed with US guns. The French then realised that they didn’t have the spare manufacturing capacity to fill this order, and instead the parts were constructed in the United States and then shipped to France to be assembled in the same factories that were used to construct the French 320mm railway guns on sliding mounts. Four sets of parts reached France in the late summer of 1918, and the plan was to assemble as many as possible before the offensives of 1919. None were completed before the armistice, although one was probably completed soon afterwards.
A variety of guns were to be used on these carriages. The Army proved the 10in guns Model 1888, Model 1888 M.I, Model 1988 M.II and Model 1895, all 34 calibres long. The Navy provided eight different models of gun, ranging from 30 to 34 calibres long. The Army guns had interrupted thread breech blocks, the Navy guns stepped threat blocks. The guns were mounted directly onto the side girders of the railway carriage (using anti-friction bearings to make it easier to elevate), and no recoil mechanism was provided on the carriage.
The gun was elevated using a rack bolted to the right of the gun. This was connected to a pinion, which was linked to a hand wheel through a series of gears. One full turn of the wheel elevated the gun by 1.37 degrees.
The carriage was built up around two structural steel box girders, which made up the sides of the structure. These were linked by a series of transoms and connected by deck plates. The carriage was supported on six axle railway trucks carried at each end.
The entire carriage could be moved along the track using a manually powered system mounted in the front of the carriage. Chains were placed below the carriage, and engaged with sprocket wheels on the carriage. Two handles were provided to turn the wheels. It took 117 turns of the handle to fully rotate the axle, and four men could move the carriage at about one meter per minute.
Before the gun could be fired, a series of ‘I-beam’ stringers were installed on the tracks, sitting on the ties, and running parallel to the tracks. Six sleepers carried below the carriage were lowered onto the ties using jacks, and the recoil was absorbed by the friction between the ‘I-beams’ and the sleepers. This meant that half of the weight of the mount was lifted off the railway tracks. To move the gun back into its original position the sleepers had to be raised.
On average the carriage moved back one meter every time it was fired. At longer ranges this didn’t make much difference to accuracy, as the shells dispersed over a fairly sizable area, so the carriage didn’t need to be returned to its original position after every shot. Although this seems like a cumbersome process, in practise it took longer to load the gun than it did to release the tension, move the carriage back into place and lower the sleepers back into place.
The big problem with this sort of carriage was that it required a specially constructed stretch of track, a curved firing track built to very high specifications with a level track, heavy rails and ties and good ballast. During the long period of static warfare on the Western Front the French were able to build these curved firing tracks wherever they might be needed, and so this didn’t cause as much delay as might be expected. In periods of more mobile warfare this type of railway gun mount thus became much less effective, as the special firing tracks needed at least two days to build.
Ammo was carried in a special ammunition car. This was linked to the gun carriage using a short track, and the shells could be moved from the ammo car to the firing platform using a special shot truck. The shells were then lifted onto a loading platform by cranes, the gun lowered to -7 degrees and the projectile slide into the breech under its own weight.
10in Gun on Sliding Railway Mount
L/30 to L/34
8.35m (329.1in) to 9.32m (367.25in)
Life of barrel at full charge
640 rounds (Army M1888)
Weight for transport
Weight in action
-7 to +54 degrees
231.45kg (510lb) HE with 25.55kg explosive
685m/s (2,250 ft/ sec)
24.58km (26,900 yards) at 45 degrees (Army M1888)
Rate of Fire
20 rounds/ hour