This gun, manufactured at Osaka Arsenal in 1939, is mounted on the Japanese Medium Tank Type 97. The tube, of monobloc construction, is fastened to the breech ring by twelve interrupted threads and secured by a lock on the right side of the tube. The breech ring is box-shaped. The breechblock of the vertical sliding type rides in two dovetailed slots in each side of the breech ring, and may be operated manually or semi-automatically.
The firing pin is automatically cocked when the breech is opened. The trigger, on the left side of the gunner’s shield, is protected by a trigger guard with a pistol grip. The recoil mechanism is a hydro-spring type.
The gun is mounted in the turret of the tank, and has a 360° traverse. It may also be freely elevated or traversed independently of the turret by means of two sets of trunnions. The inner vertical trunnions are set in a heavy steel bracket fitted to the cradle and permit a 5° left and right traverse. The bracket has a sighting window which may be closed for the gunner’s protection. The outer horizontal trunnions fit into another steel bracket and give approximately 11° elevation and 9° depression.
Although no sighting equipment was recovered with the gun, the appearance and location of the head rest, shoulder rest, and sight bracket indicate that a straight tube telescope is used.
SPECIFICATIONS
| Caliber | 57 mm | |
| Weight of tube and breech ring | 138 lbs. | |
| Weight (firing position) | 293.5 lbs. | |
| Length of tube and breech ring | 41 5/8 ins. | |
| Length (firing position) | ||
| Height (traveling position) | ||
| Height (firing position) | ||
| Width (overall) | ||
| Width of trail spread | ||
| Length of tube and breech ring | 41 5/8 ins. | |
| Rifling | R.H., uniform twist; approx. 1 turn in 28 1/2 cals. | |
| Length of rifling | 32.5 ins. | |
| No. of grooves | 20 | |
| Width of grooves | .25 in. | |
| Depth of grooves | .039 in. | |
| Width of lands | ||
| Muzzle velocity (shell) | ||
| Max. range (horizontal) | ||
| Max. range (vertical) | ||
| Rate of fire | 20 r.p.m. | |
| Traverse | 360° with turret and 5° right and left independent of turret | |
| Elevation | 11° | |
| Depression | 9° | |
| Length of recoil | 11 ins. | |
| Ammunition | H.E. and A.P.H.E. | |
| Wt. of projectile |
Japanese: p. 106.2 (August 1, 1945)