The original guns were produced by Elswick and used on Armored Cruisers built by the Italian firm of Ansaldo at the beginning of the 20th century. These were similar to other 8"/45 (20.3 cm) guns used by Ansaldo. The 8" (20.3 cm) 41st Year Type were weapons built by the Japanese and based upon information supplied by Armstrongs. These 8" (20.3 cm) guns used by the Japanese are often listed as being 40 calibers long, but according to "Naval Weapons of World War Two" they actually had a length of 45 calibers. Coastal defense guns emplaced in Japan were at least 45 calibers long.

At the Battle of Tsushima (Battle of Japan Sea) during the Russo-Japanese War of 1905, the Japanese cruiser Nisshin had three of her four 8" (20.3 cm) guns disabled due to bore prematures.

Many of these ships were disarmed as part of the Naval Limitation Treaties and their weapons then used as coastal artillery, including two twin turrets at Tokyo Bay, four single guns mounted at Tarawa and another four at Wake Island.

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

These guns were partially wire wound and had screw breech blocks.

Gun Characteristics

Designation 8"/45 (20.3 cm) EOC Patterns S, U, U1 and W
8"/45 (20.3 cm) 41st Year Type (Model 1908)
20 cm/45 (8") 41st Year Type (Model 1908)
Ship Class Used On EOC Guns: Adzuma, Asama, Iwate, Izumo, Kasuga, Nisshin, Tokiwa and Yakumo armored cruisers
41st Year Type Guns: Chikuma Class
Date Of Design N/A
Date In Service 1904
Gun Weight 18.45 to 19.1 tons (18.75 to 19.4 mt)
Gun Length oa 373.5 in (9.487 m)
Bore Length 360 in (9.144 m)
Rifling Length N/A
Grooves (48) N/A
Lands N/A
Twist Uniform RH 1 in 28
Chamber Volume N/A
Rate Of Fire about 2 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: 250 lbs. (113.4 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 1a 1905: N/A
World War II: 57 lbs. (25.85 kg) 70C2
Muzzle Velocity 1905: 2,480 fps (756 mps)
World War II: 2,493 fps (760 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
  • ^A US Army report says that the propellant charge weighed 70 lbs. (31.8 kg) but the type is not given.


Range with 250 lbs. (113.4 kg) AP
Elevation Distance
30 degree 19,700 yards (18,000 m)

Mount/Turret Data

Designation Single Pedestal Mount: Chikuma (2)
Twin Turrets: Kasuga (1), all other Armored Cruisers (2)
Weight N/A
Elevation Turrets: -5 / +30 degrees
Chikuma: N/A, but possibly the same as coastal artillery
Coastal Artillery: -5 / +24 or 0 / +30 degrees
Elevation Rate N/A
Train About +150 / -150 degrees
Train Rate N/A
Gun recoil N/A

The purpose-built coastal mountings were much simplified compared to the larger gun turrets used as coastal artillery and much of their ammunition supply and loading was manually operated.

Additional Pictures


"Naval Weapons of World War Two" and "The Battle of Tsu-Shima" articles in "Warship Volume II" all by John Campbell
"Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
"British Battleships 1860 - 1950" by Oscar Parkes
US Army Report "Survey of Japanese Seacoast Artillery, 1946"
"Navy and Army Illustrated Annuals, Volume VI - 1898"
Special help from Dave Perkins

Page History

01 August 2006 - Benchmark
27 May 2012 - Updated to latest template
29 June 2012 - Added photograph of Asama, removed photograph of Adzuma, added gun details
20 December 2015 - Added new photograph of Adzuma
31 March 2021 - Converted to HTML 5 format, added photograph of Asama bow turret