Armstrong Whitworth 12 inch /40 naval gun

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 s, but budgetary constraints delayed their introduction. The first units were instead supplied to Japan. As the Type 41 12-inch (305 mm)/40 caliber 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.

Design and development
The Type 41 12-inch naval gun was produced by Armstrong Whitworth, Elswick, Newcastle upon Tyne, as a slightly modified version of the “EOC G pattern” 12-inch guns used on contemporary Royal Navy battleships.

Japanese service
Japan purchased a total of 44 of these weapons for use on the four ships of the and, and the battleships JAPANESE BATTLESHIP Asahi and JAPANESE BATTLESHIP Mikasa. Each ship carried two guns in single mounts.

In combat at the Battle of the Yellow Sea in the Russo-Japanese War, Japanese battleships JAPANESE BATTLESHIP Asahi, JAPANESE BATTLESHIP Shikishima and JAPANESE BATTLESHIP Mikasa all had one of their main guns taken out of action due to bore prematures. The cause was traced to faulty fuses, and the problem was rectified prior to the Battle of Tsushima.

The gun was officially designated as "Type 41" from the 41st year of the reign of Emperor Meiji on December 25, 1908. It was further re-designated in centimeters on October 5, 1917 as part of the standardization process for the Imperial Japanese Navy to the metric system.

The Type 41 12-inch gun fired an 850 lb shell, with either an armor piercing, high explosive or general purpose warhead.

Royal Navy service
The gun entered service with the Royal Navy as BL 12 inch gun Mark IX on the following ships : 
 * s: Eight ships, laid down 1898 and mounting four guns each.
 * s: six ships laid down 1899, each mounting four guns.
 * s of 1904. Five of the eight ships of this class (HMS King Edward VII, HMS Commonwealth (1903), HMS Hindustan (1903), HMS Dominion (1903) and HMS New Zealand (1904)) carried the Mark IX gun.

M-class submarine mounting
The gun was in service mounted on the three M-class submarines from 1920 to 1932. 

Railway gun
Four guns were mounted on railway carriages and used by the British army in World War I on the Western Front.

Italian service
Armstrongs also sold versions of their 12 inch 40-calibre gun to Italy, to arm the (commissioned 1905) and s (commissioned 1908). The version for the s fired a heavier 417 kg shell. 

Weapons of comparable role, performance and era

 * 305 mm/40 Modèle 1893/1896 French equivalent
 * Russian 12 inch 40 caliber naval gun Russian equivalent