12"/40 (12") EOC G and G1
12"/40 (30.5 cm) 41st Year Type
30 cm/40 (12") 41st Year Type
Updated 16 December 2013

An Elswick/Armstrong design built in Britain to Patterns G and G1.  These guns and mountings were based on current British designs with small changes and were used to arm those Japanese pre-dreanoughts built in Britain.

At the Battle of the Yellow Sea (10 August 1904 Battle or Battle of Shantung) during the Russo-Japanese War, the Japanese battleships Mikasa, Asahi and Shikishima all had one of their 12" (30.5 cm) guns disabled due to bore prematures traced to faulty fuzes.  New fuzes were designed and in service prior to the Battle of Tsushima (Battle of the Japan Sea) the following year.  According to the report of RN observer Captain Parkenham, these redesigned fuzes did not improve the armor penetration, they simply prevented bore prematures.  However, Mikasa still lost one barrel during this later battle due to a bore premature of a Common shell.

The Japanese purchased at least 44 of these guns, which gave them twenty spare barrels.

Mikasa had these guns replaced with the more powerful 12"/45 (30.5 cm) when she was rebuilt following the Russo-Japanese War.

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

Actual bore length was 40.4 calibers.


Japanese pre-dreadnought Asahi
Bain News Service Photograph
Library of Congress Photograph ID LC-DIG-ggbain-19713
Click on this picture for a larger image


12"/40 (30.5 cm) turret on Asashi
IWM photograph Q 41362


IJN Mikasa
The inscription is a poem that reads, from right to left:  "Hinomoto no umi ni todoroku kachidoki wa Miitsu kashikomu koe to koso shire" - "A shout of victory at Japan Sea is a shout to glorify the empire."  The left-most three lines read:  "Early winter of 1931 - To the Mikasa Preservation Association ('Mikasa Hozon Kai'), Heihachiro," with the 2nd and 3rd characters in the second column reading "Mikasa."

When the battleship Mikasa was retired in 1926, the Mikasa Preservation Association was formed to preserve her as a memorial ship.  Admiral Togo was still alive at that time and is apparently the author of this poem.  The association was disbanded at the end of World War II but reformed in 1958.

My thanks to Dennis Khong and Eddie Khoo for translating this inscription.


Projectile Display at Yûshûkan Museum at the Yasukuni Shrine in Tokyo, Japan
From left to right:
46 cm (18.1") APC, two 12" (30.5 cm) projectiles for Mikasa and a 46 cm (18.1") HE
Picture courtesy of Taku Saito and from Museum Trip

Images at The Vickers Photographic Archive

See Pr 13

Gun Characteristics
Designation 12"/40 (30.5 cm) EOC Patterns G and G1
12"/40 (30.5 cm) 41st Year Type (Model 1908)
30 cm/40 (12") 41st Year Type (Model 1908)
Ship Class Used On Fuji, Shikishima and Mikasa Classes
Date Of Design about 1898
Date In Service 1900
Gun Weight 49 tons (50 mt)
Gun Length oa N/A
Bore Length about 485 in (12.319 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire about 1 round per minute
Type Bag
Projectile Types and Weights AP - 850 lbs. (386 kg)
HE - 850 lbs. (386 kg)
Common - 850 lbs. (386 kg)
Bursting Charge
(see Note 1)
AP - about 42 lbs. (19 kg)
HE - about 85 lbs. (39 kg)
Common - N/A
Projectile Length N/A
Propellant Charge 250 lbs. (113.4 kg)
Muzzle Velocity 2,400 fps (732 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A (probably about 100 rounds)

1) Bursters for Japanese AP and HE shells were Shimose (picric acid) while Common shells used gunpowder (black powder).  Common shells were introduced into service just before the Battle of Tsushima (Battle of the Japan Sea).  AP of this time was probably not the "capped" type.

2) As far as can be determined, Japanese 12-inch (30.5 cm) shells did not penetrate any Russian armor thicker than about 6 inches (15.2 cm).  At the Battle of the Yellow Sea (10 August Battle or Battle of Shantung), the Japanese fired 279 AP of which at least 10 hit Russian armor, mainly turrets, and not one penetrated.  At Tsushima (Battle of the Japan Sea), the Russian Battleship Orel took a hit on her 5.75-inch (15.8 cm) belt from a 12 inch (30.5 cm) shell - type unknown - which failed to penetrate.

Elevation With 850 lbs. (386 kg) AP Shell
Range @ 15 degrees about 15,000 yards (13,700 m)
Mount / Turret Data
Designation Twin Mount
   Fuji (2), Shikishima (2) and Mikasa (2)
Weight  about 184 tons (187 mt)
Elevation about -5 / +15 degrees 
Elevation Rate N/A
Train About +150 / -150 degrees
Train Rate N/A
Gun recoil N/A
Loading Angle N/A
Notes:  The Fuji class mounts were based upon the British BII mounting used for the 12"/35 (30.5 cm) Mark VIII guns on the Majestic class.  The Shikishima class mounts were based upon the British BIV mounting used for the 12"/35 (30.5 cm) Mark VIII guns on the Albion sub-class.  The Mikasa class mounts were based upon the British BVI mountings used for the 12"/40 (30.5 cm) Mark IX guns used on HMS Formidable.
Data from
"Warrior to Dreadnought:  Warship Development, 1860-1905" by D.K. Brown
"The Battle of Tsu-Shima" articles in "Warship Volume II" by John Campbell
"The Big Gun:  Battleship Main Armament 1860-1945" by Peter Hodges
"British Battleships 1860 - 1950" by Oscar Parkes
Page History

13 May 2008 - Benchmark
11 May 2009 - Added picture of Asahi
21 February 2010 - Corrected photograph caption
16 December 2013 - Added photograph of turret