These guns were manufactured in Britain by Armstrong/EOC and Vickers. They were probably similar to other Armstrong/EOC and Vickers 10"/45 (25.4 cm) guns. Japan built two types of their own design, an early one and a later version that was designated as the 41st Year Type.
All Japanese guns were redesignated as 41st Year Type on 25 December 1908. Redesignated in centimeters on 5 October 1917.
When the Japanese pre-dreadnoughts Satsuma and Aki were laid down in 1905, they were intended to be armed entirely with 12"/45 (30.5 cm) 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 instead these ships were completed with twelve 25 cm (10") guns in the amidships turrets as a cost saving measure.
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.
The data below is for the Armstrong/EOC Pattern T unless otherwise noted.
Actual bore diameter was 25.4 cm (10.0").
| Designation | 10"/45 (25.4 cm) Vickers Mark B
10"/45 (25.4 cm) Armstrong/EOC Pattern T 10"/45 (25.4 cm) Kure Arsenal 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 | Armstrong/EOC: 36.15 tons (36.73 mt) w/breech
Vickers: 35.1 tons (35.66 mt) Kure: 35.23 tons (35.80) |
| Gun Length oa | Armstrong/EOC: 467 in (1,186.2 cm)
Vickers: 464.5 in (1,179.8 cm) Kure: 467 in (1,186.2 cm) |
| Bore Length | Armstrong/EOC: 449 in (1,140.5 cm) [44.9 calibers]
Vickers: N/A Kure: 449 in (1,140.5 cm) [44.9 calibers] |
| Rifling Length | N/A |
| Grooves | (64) N/A |
| Lands | N/A |
| Twist | Armstrong/EOC: RH Uniform 1/30
Vickers: RH Increasing 0 to 1/30 Kure: RH Uniform 1/30 |
| 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 Vickers: 518 lbs. (235 kg)
AP Armstrong/EOC: 500 lbs. (226.8 kg) Common Armstrong/EOC: 500 lbs. (226.8 kg) |
| Bursting Charge | AP Vickers: N/A
AP Armstrong/EOC: 15.6 lbs. (7.07 kg) Common Armstrong/EOC: 43.2 lbs. (19.6 kg) |
| Projectile Length | N/A |
| Propellant Charge | 152 lbs. (69 kg) |
| Muzzle Velocity | Vickers: 2,657 fps (810 mps)
AP Armstrong/EOC: 2,707 fps (825 mps) Common Armstrong/EOC: 1,675 fps (511 mps) |
| Working Pressure | N/A |
| Approximate Barrel Life | N/A |
| Ammunition stowage per gun | N/A |
| Elevation | Distance |
|---|---|
| 30 degrees | about 26,900 yards (24,600 m) |
| 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.
Breyer, Siegfried
- "Battleships and Battlecruisers: 1905-1970"
- "Battleships of the World: 1905-1970"
Burt, R.A.
- "Japanese Battleships 1897 - 1945: A Photographic Archive"
Campbell, John
- "British Naval Guns 1880-1945 No 6" article in "Warship Volume VI"
- "Naval Weapons of World War Two"
Friedman, Norman
- "Naval Weapons of World War One"
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US Army Report
- Survey of Japanese Seacoast Artillery, 1946
05 September 2006 - Benchmark
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
26 October 2026 - Converted to HTML 5 format, added designation details, replaced photograph of Aki and reorganized Sources section