This gun is a naval coast defense weapon manufactured at Sasebo Arsenal. It uses semi-fixed ammunition. The barrel is of built-up construction with uniform right hand twist rifling. A manually operated, horizontal sliding block breech mechanism is used. It is unusual in that the block does not pass all the way across the rectangular breech ring. The rear of the breech ring is cut in a keyhole shape. The operator of the elevation handwheel may fire the gun by means of a lever mechanism, or it may be fired by a lanyard attached to the right side of the breechblock.
The recoil system comprises three cylinders, two located above and one below the barrel.
The mount consists of a rectangular upper carriage which is mounted on a pedestal normally embedded in a solid foundation. A traversing scale is located on the pedestal. The traversing handwheel is in a horizontal position with the vertical shaft engaging a series of gears in the base mount. Platforms attached to the upper pedestal are provided for the gun layers and move in traverse with the gun.
Fire control equipment is of the usual Japanese naval coast defense gun type.
SPECIFICATIONS
| Caliber | 120 mm (4.72 ins.) | |
| Weight (traveling position) | ||
| Weight (firing position) | ||
| Length of gun (overall) | 18 ft., 3 1/4 ins. | |
| Length of tube | 17 ft., 3 3/4 ins. | |
| Height of gun | 6 ft., 11 ins. | |
| Height (firing position) | ||
| Width (overall) | ||
| Length of rifling | 14 ft., 8 1/2 ins. | |
| No. of lands | 34 | |
| Width of grooves | ||
| Depth of grooves | ||
| Width of lands | ||
| Muzzle velocity (H.E. shell) | 2,700 f/s | |
| Max. range (horizontal) | ||
| Max. range (vertical) | ||
| Rate of fire | ||
| Traverse | 360° | |
| Elevation | 50° | |
| Depression | 10° | |
| Length of recoil | ||
| Ammunition | H.E. | |
| Wt. of projectile (H.E.) | 44.75 lbs. |
Japanese: p. 114.4 (August 1, 1945)