20 cm/50 3rd Year Type naval gun

Third year type 20 cm/50 caliber guns formed the main battery of Japan's World War II heavy cruisers. These guns were also mounted on two early aircraft carriers. The typical installation was ten 20 cm/50 guns; although Tone class cruisers carried eight while Furutaka and Aoba class cruisers carried six. After modernization, Akagi carried only six.

These were built-up guns with an inner A tube, encased by a second tube, encased by a full length jacket. Early guns were partially wire-wound, but later guns dispensed with the wire winding. The guns were breech loaded with two cloth bags of smokeless powder. Third year type refers to the Welin breech block on this gun. Breech block design began in 1914 AD, the third year of the Taishō period. This breech block design was also used on Japanese 40 cm (16 inch), 15.5 cm (6 inch), 14 cm (5.5 inch), 12.7 cm (5 inch), and 12 cm (4.7 inch) naval guns.

20 cm/50 3rd Year Type naval gun
Class Vehicle
Type Towed Artillery
Manufacturer Kure Naval Arsenal
Origin Japan
Country Name Origin Year
Japan 1926
Country Name Operational Year Retirement Year
Japan 1926 1945 View
ManufacturerName Production From Production To Quantity
Kure Naval Arsenal 300 View

Type Naval gun
Place of origin Japan
Service history
In service 1926 - 1945
Used by  Imperial Japanese Navy
Wars Second World War
Production history
Manufacturer Kure Naval Arsenal
Muroran Ironworks
Number built ~300
Weight 18 tonnes
Barrel length 10 meters (33 feet)
Shell 1 GÔ (Mark 1) : 110 kilograms (240 lb)
2 GÔ (Mark 2) : 126 kilograms (278 lb)
Calibre 1 GÔ (Mark 1) : 20-centimetre (7.874 in)
2 GÔ (Mark 2) : 8-inch (203.2 mm) 
Muzzle velocity 835 m/s (2540 ft/sec)
Maximum firing range 29 kilometres (18 mi)

End notes