Armstrong Whitworth 12-inch 40-calibre naval gun

Type 41 12-inch 40-calibre BL 12-inch Mk IX gun
Forward guns of Fuji
Type	Naval gun
Place of origin	United Kingdom, later licence-produced in Japan
Service history
In service	1900–1945
Used by	Royal Navy Imperial Japanese Navy Regia Marina
Wars	Russo-Japanese War World War I
Production history
Designer	Elswick Ordnance Company
Designed	1898
Manufacturer	Elswick Ordnance Company Vickers Woolwich Arsenal
Specifications
Mass	49 long tons (50 t)
Barrel length	40-foot-5-inch (12.32 m) bore (40 calibres)
Shell	850 pounds (390 kg) separate charges and shell
Calibre	12 inches (305 mm)
Breech	Welin interrupted screw
Elevation	−5/+15 degrees
Traverse	+150/−150 degrees
Rate of fire	1 round per minute
Muzzle velocity	Japanese service : 2,400 ft/s (732 m/s) UK service: 2,481 ft/s (756 m/s),[1] 2,612 ft/s (796 m/s) (King Edward VII class)
Effective firing range	15,000 yards (14 km); 15° elevation

The Armstrong Whitworth 12-inch naval gun of 40 calibres length was designed by and manufactured mainly by Armstrong's ordnance branch, Elswick Ordnance Company. It was intended for the Royal Navy's Royal Sovereign-class battleships, but budgetary constraints delayed their introduction. The first units were instead supplied to Japan. As the Type 41 12-inch (305 mm) 40-calibre naval gun it was the standard main battery on several early United Kingdom-built pre-dreadnought battleships of the Imperial Japanese Navy.

It later entered service with the RN as the 12-inch Mark IX, being fitted to warships of three pre-dreadnought classes prior to World War I. Also, during the war several guns were converted for use as railway guns, and, towards the end of the conflict, for use on the M-class submarine monitors.

The gun also saw service with the Italian Regia Marina, in two classes of pre-dreadnought battleships.