The Type 10 or 12 cm/45 10th Year Type naval gun was a Japanese 120 mm calibre dual purpose anti-aircraft and coastal defense gun used during the Second World War. It was derived from the 12 cm/45 3rd Year Type naval gun. The Type 10 number was designated for the year the gun was accepted, the 10th year of Emperor Taishō's reign, 1927 in the Gregorian calendar.^[1] It served as the secondary armament on a number of Japanese aircraft carriers and cruisers and as the main armament on smaller ships, in single or twin mountings.^[2]

Quick Facts Place of origin, Service history ...

Type 10 120 mm dual-purpose gun
A damaged dual purpose 120 mm gun from a four gun battery on Guam.
Type	Dual-purpose gun
Place of origin	Japan
Service history
In service	1921-1945
Used by	Empire of Japan
Wars	Second World War
Production history
Produced	1921-1945
No. built	approx 2000
Specifications
Mass	8.5 tons
Length	5.94 m (19 ft 6 in)
Barrel length	5.4 m (17 ft 9 in) L/45
Width	2.16 m (7 ft 1 in)
Height	2.34 m (7 ft 8 in)
Shell	Fixed QF ammunition 120 x 708R
Shell weight	20.6 kg (45 lb 7 oz)
Caliber	120 mm (4.7 in)
Action	Semi-automatic
Breech	Horizontal sliding-wedge
Recoil	Hydro-spring
Carriage	Pedestal mount
Elevation	-5 to +75 degrees
Traverse	360 degrees
Rate of fire	10 to 12 rounds per minute
Muzzle velocity	825 m/s (2,710 ft/s)
Effective firing range	Horizontal: 16,000 m (17,000 yd) Vertical: 8,500 m (27,900 ft)
Maximum firing range	Vertical: 10,000 m (33,000 ft)

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The weapon was originally designed for ship use and was produced in large numbers during 1944. The gun was also adapted for land use as a dual-purpose gun. The barrel was of autofretted mono-block construction and was held in a sleeve cradle mounted on a pedestal mount which permits 360° of traverse. The gun uses a hydro-spring recoil mechanism attached to the sleeve cradle and there are three recoil cylinders located on top of the breech with the two outside cylinders housing the recoil springs, and the center cylinder housing the hydraulic recuperator.^[1] The elevating handwheel is on the right side of the mount, while the traversing handwheel is on the left. To compensate for muzzle preponderance, spring equilibrators are mounted below the gun barrel. The gun is said to be well balanced, and easy to elevate. A semi-automatic horizontal sliding-wedge breech is used and Fixed QF 120 x 708R ammunition was used. The gun fired either high explosive or incendiary shrapnel shells that weighed 20.6 kg (45 lb 7 oz), with a complete round weighing 32.4 kg (71 lb 7 oz).^[3]