41 cm / 45 3rd Year Type naval gun The 41 cm / 45 3rd Year Type naval gun was a 45 - caliber breech - loading naval gun designed during World War I for the Imperial Japanese Navy . It served as the primary armament in the dreadnought s completed after the end of the war and in coast defense mountings . Two turrets and their guns were salvaged during the 1970s from the wreck of the and are currently on display in Japan . Description . The gun was of wire - wound construction and had an overall length of with a bore long . It weighed , including the Wellin - type breech . This used the Elswick three - motion short - arm mechanism , much like the British BL 18 inch Mk I naval gun designed around the same time . Chamber volume was . Initially the gun was fitted in twin - gun turrets that had an elevation range of – 2° / + 35° . It was initially equipped with the Type 88 armor - piercing , capped ( APC ) shell , that had a muzzle velocity of . This was superseded in 1931 by the Type 91 shell that weighed . It was fired at a muzzle velocity of to a range of . Also available was a high - explosive shell that had a muzzle velocity of . A special Type 3 " Sankaidan " incendiary shrapnel shell was developed in the 1930s for anti - aircraft use . The gun ' s firing cycle was one round every 24 seconds . The turrets aboard the " Nagato " - class ships were replaced in the mid - 1930s , using the turrets stored from the unfinished s . While in storage the turrets were modified to increase their range of elevation to – 3° / + 43° , which gave them a maximum range of , and their firing cycle was reduced to 21 . 5 seconds . The gun was only initially known as the 41 cm / 45 3rd Year Type naval gun before it was redesignated as the 40 cm / 45 3rd Year Type naval gun on 29 March 1922 to comply with the terms of the Washington Naval Treaty which forbade guns larger than 40 . 6 cm ( 16 in ) . Third year type refers to the Welin breech block on which design began in 1914 , the third year of the " Taishō " period . This breech block design was also used on the 20 cm ( 7 . 9 inch ) , 15 . 5 cm ( 6 . 1 inch ) , 14 cm ( 5 . 5 inch ) , 12 . 7 cm ( 5 inch ) , and 12 cm ( 4 . 7 inch ) naval guns . Service . The " Nagato " - class dreadnoughts were the only ships to use this gun , although it would have been used by the " Tosa " - class and dreadnoughts as well as the s had they not been cancelled due to the Washington Naval Treaty of 1922 . The gun was also deployed in three coast - defense turrets intended to close off the Strait of Tsushima . One turret each was deployed on Iki and Tsushima Islands while the third was mounted in Pusan , Korea . The two aft turrets from " Mutsu " s wreck were salvaged in the 1970s ; No . 4 in July or August 1970 and No . 3 in September of the following year . Turret No . 4 and its guns were restored and were installed on the grounds of the former Imperial Japanese Naval Academy at Etajima , Hiroshima . One gun from Turret No . 3 is at the Kure Maritime Museum , popularly known as the Yamato Museum , in Kure , Hiroshima while the other is at the Museum of Maritime Science in Odaiba , Tokyo . Shells into bombs . Obsolete Type 88 shells were modified in 1939 – 40 to create the Type 99 No . 80 Mk 5 armor - piercing bomb used during the attack on Pearl Harbor . The armor - piercing cap and windscreen were removed , the body was machined down and tapered to reduce weight and a new , thinner , base plug installed with two fuze s . The filling was replaced by of trinitroanisole and the bomb weighed . Beginning in 1942 an improved version of the bomb was built . Its nose was much less thick and it contained of trinitroanisole . It weighed .