Tag Archive for 'type 97'

20 mm Aircraft Machine Gun (Modified Model 97 Antitank Gun)

20 mm Aircraft Machine Gun (Modified Model 97 Antitank Gun)

This Japanese 20 mm aircraft gun is a modified version of the Model 97 antitank gun described on page 101. It is a gas-operated, full-automatic, magazine-fed, air-cooled weapon. The barrel, of monobloc construction, is fitted with a muzzle brake and attached to the receiver by means of a bushing of the interrupted screw type. The magazine fits into a rectangular opening in the top of the receiver, and the empty cartridge cases are ejected from a similar opening in the bottom. The ejector is secured to the underside of the receiver top just behind the magazine opening.

The operation of the aircraft version of this gun is similar to that of the antitank rifle. The six phases are: loading, locking, firing, unlocking, extraction, and ejection.

The first three occur on the counterrecoil, and the last three on the recoil. The gun is cocked the first time by pulling the retracting handle to the rear. This retracts the operating group to the position where the sear will engage the gas piston and hold it to the rear. After the magazine is inserted and locked in place, the gun is ready to fire.

The gun was mounted in the dorsal turret of the Bomber “Helen” on a semicircular-shaped rack, and is fixed to the rack by the lower left hand edge of the receiver. The rack is used for elevating the gun. The gun and mount are in turn mounted on the turret ring. The sight used on this gun is a reflector type sight and it is believed that there is provision made for deflection shooting. A fixed version has also been reported. Documentary evidence discloses that the ammunition for the turret gun is referred to as HO1 and the fixed as HO3.


Caliber         20 mm (.79 in.)
Weight (without mount) 74 lbs.
Length (with muzzle brake) 68 7/8 ins.
(without muzzle brake) 67 1/4 ins.
Sight radius
Principle of operation Gas
Capacity of feeding device Magazine, 15 rds.
Inverted saddle type, 50 rds.
Cooling system Air
Ammunition types AP/T; HE/T; HE/I; Ball
Rate of fire (estimated) 300 rds. per min.
Type of sight Reflector
Weight of barrel
Length of barrel 47 ins.
Length of rifling (approx.) 42 ins.
   No. of lands & grooves 8
   Depth of grooves
   Width of grooves
Chamber pressure
Muzzle velocity (estimated) 2,500-2,900 ft. per sec.
Muzzle energy
Effective range 1,000 yds.
Type of mount Dorsal turret and fixed

Japanese: p. 253 (August 1, 1945)

150 mm Mortar, Model 97 (1937)

150 mm Mortar, Type 97 (1937)

This mortar, of conventional design, is a smooth bore, muzzle-loading weapon referred to by the Japanese as a medium mortar. Although its tactical use is not fully defined, it is known to have been used in fixed concrete emplacements as a part of the island defense system.

The Model 97 is very heavy and sturdily constructed, weighing 770 pounds complete with sight. The breech cap and stud, with assembled firing mechanism, are screwed on in the normal manner. The firing pin may be adjusted to three different positions by means of a cam lock. When the lock is in the rear center position the firing pin is in a safe position; when the lock is turned to the right, the pin is “Floating,” or, in other words, may be actuated by a sharp blow on the end of the cam shaft. When the firing pin is locked forward, the operation is the same as that of a mortar with a fixed firing pin.

The bipod is of normal construction with but one exception. The elevating screw is actually two concentric screws, comparing very favorably with a single screw in stability and overall length. The traversing screw, buffer mechanism, and collar assembly are of the same design as other Model 97 Japanese mortars. The bipod and cradle may be separated for handling.

The base plate is a heavy ribbed stamping of 0.25 inch metal built up by reinforcing ribs welded to the original stamping. It has the usual ball and socket locking arrangement. The sight is a panoramic elbow telescope of three power and thirteen degree field.


Caliber         150 mm (5.906 ins.)
Weight (complete) 770 lbs.
Weight of tube 257 lbs.
Weight of bipod & traversing assembly (total) 174.5 lbs.
Weight of sight & extension 1.5 lb.
Weight of baseplate 337 lbs.
Length of tube 75.37 ins.
Length of tube (internal) 66 ins.
Length of baseplate 47.75 ins.
Width of baseplate 35.5 ins.

Japanese: p. 127 (March 1, 1945)

150 mm Self-Propelled Howitzer

Japanese 150 mm Self-Propelled Howitzer

This weapon is the 38 year type (1905) 15 cm howitzer mounted on a medium tank chassis. The chassis resembles that of the Medium Tank Model 2597 (1937), Special, described on page 8.1. The armor is riveted in the characteristic Japanese fashion, and on the chassis is of the same thickness as on the corresponding tank chassis, with a maximum of approximately one inch. On the superstructure, the gun shield has one-inch frontal armor and one-half-inch side armor.

The vehicle uses the standard V12, air-cooled, diesel engine, and the type 97 medium tank suspension, consisting of six dual rubber-tired bogie wheels on each side. The weapon mounted on this vehicle is the type 38 (1905) 15 cm howitzer, a very short weapon. It has an interrupted screw breechblock opening to the right, and uses a percussion primer. The rifling is 58 inches long and has increasing right hand twist. The maximum range of the field howitzer is reported as 6,500 yards. The maximum elevation is 30 degrees.

A self-propelled vehicle mounting a gun of 75 mm or 105 mm caliber, employing the same chassis and with a superstructure somewhat resembling the present vehicle has been reported.


Weight         15 tons
Length 18 ft.
Width 7 ft., 6 ins.
Height (overall) 93 ins.
Height of chassis 47 ins.
Height of shield 61 ins.
Ground clearance 14 ins.
Tread centers 6 ft., 7 ins.
Ground contact (approx.) 160 ins.
Width of track 13 ins.
Pitch of track 5 1/8 ins.
Track links 96
Fording depth 39 ins.
Theoretical radius of action:
   Roads 100 miles
   Cross country
   Roads 25 m.p.h.
   Cross country
Armor: gun shield
   Front plate 1 in.
   Sides 1/2 in.
Armament 15 cm Howitzer, Model 38 (1905)
Ammunition (Rds).
Engine V12, air-cooled, diesel
Transmission 4 speeds forward; 1 reverse (high and low range)
Steering clutch brake
Crew probably 5

Japanese: p. 8.2 (August 1, 1945)