Armstrong Whitworth 12 inch /40 naval gun

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Type 41 12-inch 40-calibre
BL 12 inch Mk IX gun
Japanese battleship Fuji Forward 12 inch guns.jpg
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
Woolwich Arsenal
Weight 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 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[edit]

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[edit]

Japan purchased a total of 44 of these weapons for use on the four ships of the Fuji and Shikishima class, and the battleships Asahi and Mikasa. Each ship carried four guns in twin turrets.

In combat at the Battle of the Yellow Sea in the Russo-Japanese War, Japanese battleships Asahi, Shikishima and Mikasa all had one of their main guns taken out of action due to bore prematures.[2] 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 25 December 1908. It was further re-designated in centimetres on 5 October 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-pound (390 kg) shell, with either an armour-piercing, high-explosive or general-purpose warhead.

United Kingdom service[edit]

Royal Navy service[edit]

Forward guns of HMS Queen

The gun entered service with the Royal Navy as "BL 12 inch gun Mark IX"[note 1] on the following ships :

M-class submarine mounting[edit]

Sectioned model showing mounting on submarine HMS M1

The gun was in service mounted on the three M-class submarines. HMS M2 and M3 had their guns removed in 1927-28.

Railway gun[edit]

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

United Kingdom ammunition[edit]

Italian service[edit]

Armstrongs also sold versions of their 12-inch 40-calibre gun to Italy to arm the two Regina Margherita-class (commissioned 1905) and the four Regina Elena-class battleships (commissioned 1908). The version for the Regina Elena class fired a heavier 417 kg (919 lb) shell. The Regina Margueritas were lost during the war, the Regina Elenas scrapped after the war.

See also[edit]

Weapons of comparable role, performance and era[edit]


  1. ^ I.e. Mark 9 : Britain used Roman numerals to identify Marks (models) of its ordnance - this was the 9th 12-inch breech-loading naval gun in service with the Royal Navy


  1. ^ 2,481-foot-per-second (756 m/s), 850-pound (390 kg) projectile, with 211 lb (96 kg) cordite Mk I size 50 & 3¾. Text Book of Gunnery, 1902.
  2. ^ Corbett, Julian Stafford (1994). Maritime Operations in the Russo-Japanese War 1904–05. Naval Institute Press. pp. 391–392. ISBN 1557501297. 


External links[edit]