These guns were a Vickers design, manufactured in Britain and were probably similar to other Vickers 10" (25.4 cm) guns.

When the Japanese pre-dreadnoughts Satsuma and Aki were laid down in 1905, they were intended to be armed entirely with 12"/45 guns, which would have made them the first "all big-gun" battleships in the world. However, the cost of the Russo-Japanese War nearly ruined Japan so these ships were completed with twelve 25 cm (10") guns in the amidships turrets as a cost saving measure.

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

After these ships were scrapped in the 1920s some of their turrets were then used as coastal artillery. Four turrets were emplaced with two from Aki used to guard the Tokyo Bay area.

Actual bore diameter was 25.4 cm (10.0").

Gun Characteristics

Designation 10"/45 (25.4 cm) Vickers
10"/45 (25.4 cm) 41st Year Type (Model 1908)
25 cm/45 (10") 41st Year Type (Model 1908)
Ship Class Used On Satsuma and Katori Classes
Date Of Design about 1905
Date In Service 1909
Gun Weight 22 tons (22.5 mt)
Gun Length oa N/A
Bore Length about 450.0 in (11.430 m)
Rifling Length N/A
Grooves (64) N/A
Lands N/A
Twist Uniform RH 1 in 28
Chamber Volume N/A
Rate Of Fire about 1.5 rounds per minute 1
  • ^The post-war US survey of Japanese Seacoast Artillery states that the coastal artillery turrets could fire 2 rounds per gun per minute for brief periods.


Type Bag
Projectile Types and Weights AP: 518 lbs. (235 kg) AP Shell
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 152 lbs. (69 kg)
Muzzle Velocity 2,657 fps (810 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A


Range with 518 lbs. (235 kg) AP
Elevation Distance
30 degrees about 26,900 yards (24,600 m)

Mount/Turret Data

Designation Twin Mount: Katori (2) and Satsuma (6)
Weight N/A
Elevation about -5 / +30 degrees 1a
Elevation Rate N/A
Train About +80 / -80 degrees
Train Rate N/A
Gun recoil N/A
Loading Angle N/A
  • ^Mountings used for coastal artillery had their maximum elevation increased to +35 degrees. These coastal mountings were much simplified compared to the larger gun turrets used as coastal artillery and much of the ammunition supply and loading was manually operated.

External Pictures


Data from:

  • "Battleships and Battlecruisers: 1905-1970" and "Battleships of the World: 1905-1970" both by Siegfried Breyer
  • "Naval Weapons of World War Two" by John Campbell


  • US Army Report "Survey of Japanese Seacoast Artillery, 1946"

Page History

05 September 2006
05 January 2009
Added the number of mountings on Katori
18 April 2010
Corrected picture caption
20 January 2012
Corrected typographical error
29 June 2012
Added gun details and information about use as coastal artillery
24 December 2015
Changed Vickers Photographic Archive links to point at Wayback Archive