41 cm/45 3rd Year Type naval gun

• Name — 41 cm/45 3rd Year Type naval gun • Origin — Japan • Type — Naval gun Coast-defense gun • Is Ranged — YES • Is Artillery — YES • Service — 1920–1945 • Used By — Imperial Japanese Navy • Wars — World War II • Number — about 40 • Weight — 102000 kg • Length — 18.84 m • Part Length — 18.394 m (45 calibers) • Cartridge — Separate-loading, bagged charge • Cartridge Weight — 1020 kg • Caliber — 41 cm • Rate — 1 round per 24 seconds • Velocity — 780 - • Range — 30200 m • Max Range — 38400 m • Breech — Welin breech block • Elevation — –2° to +35° (later –3° to +43°) • Filling Weight — 243 lb

The Nagato-class dreadnoughts were the only ships to use this gun, although it would have been used by the Tosa-class and battleship 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. Mutsus original number 4 turret, removed during her interwar refit, is on display on the grounds of the former Imperial Japanese Naval Academy at Etajima, Hiroshima, where it was placed as a training aid in the 1930s. The two aft turrets from Mutsus wreck were salvaged in the 1970s; No. 4 in July or August 1970 and No. 3 in September of the following year. Both were scrapped. 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.

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 fuzes. The filling was replaced by 50 lb of trinitroanisole and the bomb weighed 796.8 kg. Beginning in 1942 an improved version of the bomb was built. Its nose was much less thick and it contained 35.7 kg of trinitroanisole. It weighed 811.2 kg.

• BL 16 inch Mk I naval gun: British equivalent • 16"/45 caliber Mk 1, 5 & 8 gun: American equivalent

41 cm/45 3rd Year Type naval gun is classified as a rifled breech loader, naval artillery or coastal artillery weapon. Associated with Empire of Japan.