Japan 8"/45 (20 cm) EOC Patterns S, U and W and 8"/45 (20.3 cm) 41st Year Type

Japan
8"/45 (20.3 cm) EOC Patterns S, U, U¹ and W
8"/45 (20.3 cm) 41st Year Type
20 cm/45 (8") 41st Year Type
Updated 29 June 2012

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.

Armored Cruiser Asama
Photograph from Allan C. Green collection of glass negatives
State Library of Victoria Image H91.325/1058

Stern 8"/45 (20.3 cm) Mounting on IJN Armored Cruiser Nisshin on 24 October 1908
Ship's officers with USN officers from USS Missouri (B-11) during "Great White Fleet" around the world cruise
Note the landing guns on the upper platform
U.S. Naval Historical Center Photograph # NH 82511

8"/45 (20.3 cm) gun under construction at the Elswick Works
Photograph courtesy of Dave Perkins

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 (see Note)	about 2 rounds per minute
Note: 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.

Ammunition .

Type	Bag
Projectile Types and Weights	AP - 250 lbs. (113.4 kg)
Bursting Charge	N/A
Projectile Length	N/A
Propellant Charge (see Note)	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
Note: A US Army report says that the propellant charge weighed 70 lbs. (31.8 kg) but the type is not given.

Range .

Elevation	With 250 lbs. (113.4 kg) AP Shell
Range @ 30 degrees	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
Note: The 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.

Data from
"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
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US Army Report "Survey of Japanese Seacoast Artillery, 1946"
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"Navy and Army Illustrated Annuals, Volume VI - 1898"
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Special help from Dave Perkins

Page History

01 August 2006 - Benchmark
27 May 2012 - Updated to latest template
29 June 2012 - Added picture of Asuma, removed picture of Adzuma, added gun details