Canon de 138 mm Modèle 1910 naval gun

The Canon de 138 mm Modèle 1910 was a medium calibre naval gun of the French Navy used during World War I and World War II. It was carried by the dreadnoughts of the Courbet and Bretagne classes as their secondary armament and planned for use in the Normandie-class battleships. It was used as the primary armament for the Arras-class sloops and planned for the light cruiser Lamotte Picquet that was canceled in 1915. It was also used in coast defense batteries during both World Wars.

Design
The 55 caliber Mle 1910 used the typical built-up construction of its time. It had a screw breech and used separate-loading ammunition. In the battleships it was installed in armored casemates, using central pivot mounts, but no details are available. Presumably a variant of this mount was used for the sloops. Initially the casemate mount had a range of elevation from -10° to +15°, but this was later changed to -7° to +25°. The casemate mount could traverse a total of 160°.

Ammunition
The 10.4 kg propellant charge for the Mle 1910 was contained in a cartridge case that would be used for all succeeding French guns of this caliber. Of course the actual amount of powder would vary with each gun, but it standardized the chamber size for all 138.6 mm French guns.

Coast defense duties
Twenty Mle 1910 guns were used by the Germans as coast defense guns along the French Mediterranean coast, although it is unclear if these guns were simply taken over by the Germans or if they were emplaced by them.

In 1942 14 guns removed from the battleships Courbet and Paris were installed in coast defence batteries at Dawlish, Hayle, Padstow, Par, Sidmouth, Port Talbot and Whitehaven in the UK. These guns were returned to France in September 1945.