The Canon de 42 C model 1867 was a French super-heavy built-up naval gun, designed and produced by the Ruelle Foundry. It was the centerpiece of the French naval artillery exhibition at the 1867 Paris Exposition Universelle. Only two examples were ever built, and the gun proved unsuitable for active service.
Design and Context
The gun was developed in response to the increasing use of iron armor on warships following the Crimean War (1853–1856). It was constructed according to the same design principles as the French modèle 1864–1866 system of cast-iron breechloading rifled guns reinforced by steel rings, though it was never officially adopted into service. Some contemporary observers suggested the gun was ordered after the French government learned of Krupp's plans to send a "monster gun" to the 1867 exposition.
Specifications
| Attribute | Value |
|---|---|
| Type | Coast-defense gun (prototype) |
| Place of origin | France |
| Manufacturer | Ruelle Foundry |
| Unit cost | 31,300 Francs |
| Number built | 2 |
| Mass | 38 t (37 long tons; 42 short tons) |
| Caliber | 420 mm (17 in) |
| Barrel length | Smoothbore (initially); intended to be rifled with 5 parabolic grooves |
| Traverse | 360° (on turntable) |
| Effective range | 6–8,000 m (intended after rifling) |
Barrel and Construction
The barrel was a built-up design, consisting of a cast-iron core reinforced by two layers of steel frettes (hoops) that were shrunk onto the tube. The barrel alone weighed 38,200 kg. The gun was originally a smoothbore breechloader — an unusual combination — though it was intended to be rifled later. Spherical iron bullets were displayed alongside it at the exposition, but elongated 42 cm grenades were also shown.
Carriage
The gun was mounted on an iron and sheet-metal carriage that slid over a frame (slide), together weighing 20,000 kg. The slide sat on a turntable allowing 360° traverse. Elevation was controlled by a roller chain moved by cogwheels on either side of the carriage.
Projectiles
- With a 50 kg powder charge, the gun could fire a spherical iron bullet of 250 kg.
- After rifling, it was expected to fire an ogive (pointed) projectile of 750 kg, but this was abandoned after analysis showed the barrel was insufficiently strong relative to the projectile weight.
Production and Transport
The first gun was cast on 16 March 1867, requiring all ten furnaces of the Ruelle Foundry to operate simultaneously — a spectacular event witnessed by many visitors. The casting consumed 11,245 kg of coal and took 3 hours and 2 minutes. A second gun was cast on 30 March 1867.
The first gun left Ruelle on 2 July 1867, drawn by 40 heavy draft horses to the Angoulême railway station, then transported to Paris on two special freight wagons, arriving on 9 July.
Service History
After the exposition, the Paris gun was moved to Cherbourg for planned testing (including a proposal to test it aboard the ironclad Rochambeau), but these tests do not appear to have been carried out. The second gun was sent to Rochefort and then to the artillery range at Gâvres, where a planned experiment with a 304 kg projectile also seems not to have been executed. Neither gun ever entered active service.
