This gun was jointly designed by the British armament firms of Armstrong and Vickers. The design was generally similar to the British 12"/50 (30.5 cm) Mark XI. All guns were produced by Nihon Seiko Shi (Japanese Steelworks), the Japanese subsidiary of W.G. Armstrong-Whitworth and Vickers, Sons & Maxims.

These guns were used on Japan's last pre-dreadnoughts Kawachi and Settsu. This class had a mixed battery, with the 30.5 cm/50 (12") guns in the bow and stern turrets and 30.5 cm/45 (12") guns in four amidships turrets. This mixed battery was a result of the poor financial situation in Japan resulting from the Russo-Japanese War which limited the Navy to manufacturing only a few of the higher-performance weapons. This combination of 45 and 50 caliber guns would have made centralized fire control on these ships very difficult.

Wire-wound construction with autofretted barrel and used a Welin breech mechanism. Coastal artillery used hydraulic power for the breech and rammer. Ammunition used electrical primers.

After these ships were scrapped, the two turrets from Settsu were given to the Army who used them in the coastal defenses at Nagasaki and Tsushima Island.

Redesignated as 41st Year Type on 25 December 1908. Redesignated in centimeters on 5 October 1917.

Gun Characteristics

Designation 12"/50 (30.5 cm) Armstrong/Vickers
12"/50 (30.5 cm) 41st Year Type (Model 1908)
30 cm/50 (12") 41st Year Type (Model 1908)
Official Designation: 50 caliber 41st Year Type 30 cm Gun
Ship Class Used On Kawachi Class
Date Of Design about 1905
Date In Service 1912
Gun Weight 67 tons (68 mt)
Gun Length oa N/A
Bore Length about 600.0 in (15.240 m)
Rifling Length N/A
Grooves (72) N/A
Lands N/A
Twist Uniform RH 1 in 28
Chamber Volume N/A
Rate Of Fire 2 rounds per minute 1
  • ^The post-war US survey of Japanese Seacoast Artillery states that these guns could fire 2 rounds per gun per minute.


Type Bag
Projectile Types and Weights APC 1a - 850 lbs. (386 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 294 lbs. (133.5 kg)
Muzzle Velocity 2,850 fps (869 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
  • ^The post-war US survey of Japanese Seacoast Artillery states that these guns fired 881.6 lbs. (400 kg) AP shells. Whether this was the naval shell or a new Army projectile is not defined. Muzzle velocity with a 294.5 lbs. (133.6 kg) charge was 2,800 fps (850 mps).


Range of Naval APC projectiles
Elevation Range
25 degrees about 27,600 yards (25,240 m)
Range of Coastal Artillery APC projectiles
Elevation Range
33 degrees 32,200 yards (29,440 m)

Mount/Turret Data

Designation Twin Mount
   Kawachi (2)
Weight N/A
Elevation Ships: about -5 / +15 degrees

Coastal artillery: 0 / +33 degrees

Elevation Rate N/A
Train About +150 / -150 degrees
Train Rate N/A
Gun recoil N/A
Loading Angle N/A

Additional Pictures


"Battleships of the World: 1905-1970" by Siegfried Breyer
"Naval Weapons of World War Two" by John Campbell
"The Big Gun: Battleship Main Armament 1860-1945" by Peter Hodges
"Taisho Gan-nen Kaigun Dai Enshu Shashin-cho" (Photograph album of the great naval drill in the first year of Taisho [1912])
US Army Report "Survey of Japanese Seacoast Artillery, 1946"
Iki fortress Kurosaki Fort
Special help by Mozi Hashimoto and TZoli

Page History

26 September 2007 - Benchmark
11 May 2009 - Replaced poor side view photograph of Settsu with a better one of Kawachi
30 June 2012 - Added gun details and information about use as coastal artillery
26 April 2014 - Corrected captions on photographs and added new photograph of stern turret on Kawachi
01 November 2016 - Converted to HTML 5 format
20 April 2022 - Added blueprint image