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The 4.7in Howitzer on Railway Mount Model 1917 was a Model 1913 howitzer mounted on a simple railway carriage, and was used as a coastal defence weapon at Panama after the American entry into the First World War.
The 4.7in Howitzer Model 1913 was a wire wound gun, with an interrupted thread breech block and a mechanical firing mechanism. It was normally used on a static pivot mounting as a coastal defence gun, but this railway mount was produced to provide a more mobile version.
The howitzer was carried on a pedestal, with the recoil mechanism built into the top carriage, along with the elevating and traversing mechanisms.
The 4.7in Howitzer used a hydro-spring recoil system that was combined into a single cylinder. The cylinder was fixed to the barrel, and recoiled with the gun, while the piston was fixed to the mount and remained stationary as the gun was fired. The counter-recoil spring was attached to the cylinder, and the head of the cylinder acted as the piston for the spring. The system allowed for 12in of recoil.
The weapon had to be loaded at -10 degrees of elevation, and had a screw elevation system that could reach up to +40 degrees, using hand wheels mounted on both sides of the carriage.
The gun was mounted on a pedestal that could be traversed using another hand wheel, and could traverse through 360 degrees.
The railway car was made up of five main parts. The gun was carried on a cast steel central section that was dropped down low to the track (the base of the pedestal was built into this section). This was connected to two steel two axle bogie sections, with platforms that were higher than the gun mount. The three sections were connected by two side plates.
There were three armoured plates at each end of the car, and two more on the sides of the central section. In the raised position they provided protection for the crew, and were equipped with holes to fire machine guns through. In the lowered position they served as the fighting platform for the gun.
In action the entire mount was lowered, and clamped to the railway track. There were side arms that could be extended to act as outriggers. There were six pads under the central section of the car which took the weight of the entire thing when it was lowered. It took 45 minutes to install the gun and 25 minutes to prepare it for movement.
Four 4.7in Howitzer railway mounts were almost complete when the United States entered the First World War in 1917. They were completed and sent to Panama to help guard the Canal Zone.
Name |
4.7in Howitzer on Railway Mount Model 1917 |
Calibre |
4.7in |
Barrel Length |
L/22.5 |
Gun Length |
2.82m (111.4in) |
Weight in action |
20,600kg (45,495lbs) |
Elevation |
-10 to +40 degrees. |
Traverse |
360 degrees |
Shell Weight |
27.23kg (60lb) AP (1.47kg of explosive) |
Muzzle Velocity |
396 m/sec (1,300 ft/ sec) |
Maximum Range |
9.14km (10,000 yards) |
Rate of Fire |
60 rounds per hour |