Tag Archive for 'Japanese'

20 cm Rocket Projectile and Launcher

Japanese 20 cm Rocket Projectile and Launcher

This ground-launched rocket is fired from a trough shaped launcher approximately 7 feet long, which weighs approximately 175 pounds. The Japanese claim a range of 1,800 meters (1,970 yds.) at 50° elevation. The rocket is spin-stabilized, rotating in a clockwise direction. The complete round, without fuze, is approximately 41 inches long and weighs 198.3 pounds.

The projectile has a straight body and an ogival nose. It is fitted with a centrifugally armed point detonating fuze. In addition to this standard fuze, the Type 91 Time, Type 100 Combination, and Type 88 P.D. fuzes will also fit the fuze pocket. However, it is not known whether the rocket will produce sufficient setback to arm these fuzes. The explosive charge, Type 91 (trinitroanisol), is cast directly into the lacquered interior of the case. The base plate which screws into the projectile body is also threaded to take the motor.

The motor body, a straight cylinder, is closed at the rear by a base plate to which a grid is attached. A perforated cup fits against the motor closing plate at the forward end. Seven sticks of propellant (nitroglycerine, nitrocellulose, NaCl, and centralite) fit securely into the combustion chamber between the perforated cup and the grid. Six sticks form a circle around an identical central stick; all have only a single axial perforation.

The motor base plate of hardened steel has six offset nozzles and a central threaded opening for a percussion type primer. Ignition is mechanical and from the forward end. A black silk powder bag lashed to the perforated cup forms the ignition charge.


Weight of projectile without fuze         49.9 kg.–110 lbs.
Weight of high explosive filling 17.5 kg.–38.6 lbs.
Overall length of projectile without fuze 588.0 mm–23.14 ins.
Minimum diameter of orifices 15.0 mm–.591 ins.
Angular cant of nozzles 25°
Diameter of body 210.5 mm (approx. 8.30 ins.)
Wall thickness 12.0 mm–.472 in.
Overall length of motor body 460 mm–18.11 ins.
Weight with propellant 40.0 kg.–88 lbs.
Weight of propellant 8.3 kg.–18.3 lbs.
Weight of black powder ignition charge 50.6 grams–1.77 ozs.
Wall thickness 10.0 mm–.39 in.
Length of propellant sticks 290.0 mm–11.41 ins.
Diameter of propellant sticks 58.0 mm–2.28 ins.
Diameter of perforation 11.0 mm–.43 in.
Weight of propellant sticks (each–varies slightly) 1.162 kg.–2.56 lbs.

Japanese: p. 352 (April 1, 1945)

Rocket Launcher and Rocket Motor Model 10

Rocket Launcher and Rocket Motor Model 10

This is a device designed to propel the 60 kg. (132 lbs.) aircraft bomb out of an inclined trough.

The launcher is constructed of wood and metal with legs made of iron pipe. The rear is attached by a pin to a base plate with six wedge cut ground pins. The launcher channel is a right angle trough about twenty feet long with a motor and bomb positioner made of 1/8-inch pierced sheet metal. This is “V” shaped, (The motor and bomb positioner is not shown in the schematic sketch above.) slightly over four feet long, and hinged at three points on the lower right side of the launcher. Elevation is controlled by cables run from the base plate to the legs, and between the legs.

The rocket motor resembles a blunt, short-bodied bomb. The propellant container is a cylinder with a cap welded on the front and a tail assembly and venturi tube secured on the rear. The propellant which weighs 12.94 pounds consists of three cylindrical sticks tied in a yellow silk bag. It is ignited by an igniter pad and an igniter fuze in the forward part of the motor by means of wires leading to a small hand blasting machine. When fired the motor propels the bomb from the launcher and then drops off. Ranges up to 1,300 yards are claimed by the Japanese for this device, but it is felt that little, if any, accuracy may be expected. It is evidently designed to deliver fire on beachheads and other similar wide targets at fairly short ranges.


Length of launcher (overall)       19 ft., 10 ins.
Width at leg shoes8 ft., 5.5 ins.
Height at 30° range setting11 ft.
Length of leg12 ft., 4 ins.
Diameter of leg1.75 ins.
Width outside of trough at base10 ins.
Width outside of trough at front7.5 ins.
Width inside of trough at base8.5 ins.
Width inside of trough at front6 ins.
Length of cable from baseplate to leg20 ft., 3 ins.
Length of motor and bomb positioner (overall)4 ft., 3 ins.
Length of motor (overall)33 ins.
Length of propellant cylinder11.5 ins.
Diameter of propellant cylinder (outside)7.44 ins.
Diameter of venturi tube (outside)1.5 ins.
Length of tail fin11.75 ins.
Width of tail fin3.625 ins.
Width of tail, fin to fin11.875 ins.

Japanese: p. 351 (April 1, 1945)

81 mm Antiaircraft Mortar Projectile

81 mm Antiaircraft Mortar Projectile

This antiaircraft projectile, fired from the 81 mm barrage mortar, is composed of three sections. The rear portion consists of a primer, black powder charge, propelling charge, 15-second delay train, and a black powder ejecting charge. The explosive cylinder, or middle section, comprises a 40-second delay pellet in a central cylinder and three H.E. pellets cast around the delay element. The forward end section contains a wooden nose plug, two parachutes, and a suspension cord.

The projectile is slid down the mortar tube in a manner similar to the firing of a standard mortar shell. Upon striking the firing pin, the primer is ignited, and it, in turn, sets off the loose black powder in the base of the round. The black powder ignites the propellant and the 15-second delay train. The shell is propelled from the mortar and continues in flight until the delay train ignites the ejecting charge which forces out the wooden nose plug, the two parachutes, the suspension cord, and the explosive cylinder. At the same time, the 40-second delay pellet is ignited. The explosive cylinder is suspended by a small parachute attached to the cylinder by 12-inch strands, and by a larger parachute attached to the cylinder by the 30-foot suspension cord. The end of the suspension cord is covered with match composition and acts as a pull igniter. If an airplane strikes the suspension cord of the floating high explosive assembly, the jerk on the cord pulls the end of the cord through the primer, causing detonation of the high explosive. If the pull igniter is not functioned, the burning train of the 40-second delay pellet reaches the detonator and sets off the explosive cylinder.

An 81 mm flare shell, identical in external appearance except for color markings, is also used. It contains two parachutes and a flare, apparently of a magnesium composition. When the projectile is in flight, a 15-second delay train sets off an ejecting charge of black powder which forces out the nose plug, parachutes, and flare. The burning of the ejecting charge ignites the flare, which floats earthward on the parachutes.


Caliber        81 mm
Length (overall) 21 3/8 ins.
Diameter of cylinder 1 9/16 ins.
Size of fins 7/8 in. x 4 3/4 ins.
Color Black with tan nose plug

Japanese: p. 310.1 (May 1, 1945)

Antitank “Lunge” Mine

WWII Japanese Antitank Suicide Lunge Mine

Japanese Antitank Suicide Lunge MineThis suicide mine, an antitank device used by Japanese Close-quarter Combat Units, consists of a conical-shaped hollow charge encased in a steel container, and a wooden handle. Three legs equally spaced around the base of the charge provide proper stand-off distance. A well in the apex of the charge contains the detonator.

The firing mechanism, quite simple in construction, consisting of a needle type striker, a shear pin, and a safety pin, is housed in a metal sleeve. This sleeve, which holds the mine” and the handle 2.4 inches apart, slips over the end of the handle and is held in place by the shear pin and safety pin; it is attached to the body of the mine by a threaded connecting ring.

To operate the mine, the soldier must first remove the safety pin, and then, using bayonet tactics, lunge forward striking the mine squarely against the tank. When the legs of the mine strike the target, the handle is driven forward breaking the shear pin, and the striker is driven into the detonator, initiating explosion of the mine.

Reports indicate that when head-on contact is made, the mine will penetrate 6 inches of steel plate; with contact at a 60° angle, steel plates of approximately 4 inches can be penetrated.


Length of mine body (approx.)        12 ins.
Diameter of base of body (approx.) 8 ins.
Length of handle59 ins.
Diameter of handle1 1/4 ins.
Weight of explosive charge6 1/2 lbs.
Length of legs5 1/4 ins.
Weight of mine (total)14.3 lbs.

Japanese: p. 308.3 (May 1, 1945)

High Explosive Rifle Grenade Model 3

High Explosive Rifle Grenade Model 3This grenade, designed to be fired from Models 38 and 99 rifles by means of a spigot launcher and wooden bullet, is similar in use and operation to the Model 91 rifle grenade. However, it is smaller and has a smooth-wall body rather than the serrated type. It contains a cyclonite primer enclosed in a brass container, a tetryl booster, and a three-ounce bursting charge of cast TNT; it is also fitted with an instantaneous fuze and a tail assembly with four fins spot welded to the rear part of the tube.

The grenade is armed by the removal of a safety fork. On impact, an inertia block is forced into the fuze body shearing a brass shear wire and driving the firing pin into the detonator.


Diameter of grenade body         1.63 ins.
Length of grenade body 2.43 ins.
Wall thickness 1/8 in.
Overall length of grenade 7.88 ins.
Weight of grenade without explosive 14 ozs.
Weight of explosive body without explosive 10 ozs.
Length of fin assembly 4 15/16 ins.
Outside diameter of tube 1 13/16 ins.
Inside diameter of tube 1 1/16 ins.
Width of tail assembly 2 1/8 ins.
Length of tail fin 2 3/8 ins.
Width of tail fin 1/4 in.
Material of construction Steel
Weight of main charge 3 ozs.
Weight of primer 3 gr.
Weight of booster 1 gr.

Japanese: p. 304.2 (April 1, 1945)

Pottery Hand Grenade

pottery-hand-grenadeThis hand grenade, made of terra cotta, and, like the Model 3 Flower Pot Land Mine, filled with Type 88 explosive, is assumed to be a Navy weapon. Except for the neck at the top, it is spherical, consisting of two halves baked together. It is light brown, in color, and lightly glazed both inside and out. The grenade is encased in a straw-colored, waterproof rubber sack.

The ignition system consists of a match composition and scratch block, a 4-5-second delay element, a lead azide initiator, and a tetryl booster. All are encased in a rubber tube except the match composition which is lacquered into the neck of the grenade. In order to operate the grenade, the small rubber covering is removed from the top and the scratch block is struck on the protruding match composition, igniting the delay element.


Height (base to top of neck)         99 mm—3.9 ins.
Diameter 79 mm—3.1 ins.
Total weight 1 lb.
Weight of explosive 100 grams—3.5 ozs.
Pottery thickness 7/16 inch

Japanese: p. 304.2 (April 1, 1945)

Conical Antitank Hollow Charge Hand Grenade

Japanese Conical Antitank Hollow-Charge Hand Grenade

This Japanese antitank grenade consists of a Pentalite (50/50 TNT & PETN) explosive charge cast around a thin aluminum cone, a wooden stand-off head, a fuze, and a tail attachment.

The explosive charge, which is shaped in the form of a hollow truncated cone, has a covering of thin waxed paper and a well in the upper end to receive the booster of the fuze. A cast ring pellet surrounds the cyclonite booster. The fuze, an all-ways impact type, is constructed in two parts which are threaded together. It will not function unless the mine has attained a velocity of approximately forty feet per second, and strikes a hard surface. The wooden base provides proper stand-off distance and has a central hole of slightly smaller diameter than that of the cone.

The grenade is encased in a silk bag, either white or olive drab in color, and closed by a draw-string at the bottom. A tail made of hemp is tied around the top of the grenade to provide stability in flight. The device, which will penetrate about 2 inches of armor plate, should be thrown from a distance of approximately ten meters.

A modified version of this grenade, referred to as the Type B, has been recovered. It differs from the grenade previously encountered in the Philippines in the following respects: it is smaller, the cover is yellow silk instead of canvas, the fuze is screwed into a metal seat on top of the mine, the fuze body is metal with a single-pronged safety pin, and the detonator tube is larger.

According to reports, there is also a larger grenade of the same type which has a Type 94 explosive charge.


           Large Grenade          Small Grenade
Length of grenade 6 3/4 ins. 5 7/8 ins.
Length of tail 14 ins.  
Diameter at base 4 3/8 ins. 4 ins.
Length of fuze 1 7/8 ins. 1 7/8 ins.
Length of cone 3 3/4 ins. 2 3/8 ins.
Diameter of cone 2 3/8 ins. 2 ins.
Cone angle, apex 30° 38°
Weight complete 1.25 kg. .84 kg
Weight of grenade 1.14 kg. .76 kg.
Weight of fuze 42.3 grams 42.3 grams
Weight of explosive .87 kg. .60 kg
Weight of cone 141.7 grams 42.5 grams
Weight of base 56.7 grams 50.0 grams
Weight of booster 5.1 grams 5.1 grams

Japanese: p. 304.1 (April 1, 1945)

20 mm Aircraft Cannon Type 99 Mk. II

20 mm Aircraft Cannon Type 99 Mk. II

This is a gun of higher power than the Type 99 Mk. I, 20 mm cannon. Like the earlier gun, it operates on the Oerlikon principle and is found both with drum type magazine feed (Mod. III—top photo) and with belt feed (Mod. IV—lower photo).

The principal differences between this model and the Mk. I consist of a longer barrel and a longer chamber. The barrel protrudes 18 inches beyond the leading edge when mounted in the wings of fighter aircraft. The projectiles used are identical to the Mark I, but the cartridge employed contains approximately 40% more propellant than the older type, thereby increasing the velocity of the Mk. II 500 to 700 foot seconds. The muzzle velocity of the weapon varies from 2,500 to 2,700 foot seconds depending upon the type of projectile used. The gun has been found in ZEKEs and HAMPs. It is probably fitted in RUFEs and as a flexible gun in the tail turret of BETTY.


Caliber         20 mm (.787 in.)
Weight of gun 67 lbs.
Length of gun (overall) 73 ins.
Length of barrel 47 ins.
Length of rifling 41.5 ins.
Number of grooves 9
Depth of grooves 0.026 in.
Twist of rifling Right hand
Principle of operation Blow back
Feeding device French drum or belt
Capacity of drum 100 rds.
Cooling system Air
Sights Reflector type
Charging mechanism Pneumatic
Firing system Flexible cable
Effective range (est.) 600-700 yds.
Rate of fire (est.) 400-500 r.p.m.
Ammunition Ball, A.P., A.P./I., T., H.E., H.E./T., H.E./I.

Japanese: p. 254 (August 1, 1945)

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)

20 mm Aircraft Cannon Ho 5 (Browning Principle)

20 mm Aircraft Cannon Ho 5 (Browning Principle)

This weapon, an improvement on the 12.7 mm Japanese copy of the U.S. Cal. .50 aircraft machine gun, is a recoil-operated, disintegrating metallic link belt-fed, air-cooled, aircraft machine cannon. It is mounted as a fixed weapon and as such it is fired electrically by remote control.

The recoil mechanism consists of a metal cylinder into which is fitted a coil spring. Through the center of this extends a 5/16-inch rod which screws into a brass bushing. The rod extends through the spring follower which rests on the coil spring and is secured by two lock nuts. Buffering action takes place in the recoil direction only. There is no quick change barrel. Because of the weight of the bolt and the heavy recoil spring, a booster is used, this being found in the flash hider.

The gun has a high cyclic rate of fire, muzzle velocities of 2,304 f/s (A.P.), 2,430 f/s (H.E.), and a penetration performance of 7/8-inch homogenous plate at 20° at 200 yards; 1/2-inch at 20° at 580 yards. The maximum weight lifting capacity of the belt is 62 pounds.

The disassembly of the weapon is the same as the Browning Cal. .30 and Cal. .50 machine guns with a few minor exceptions. The Japanese weapon has no back plate latch. The back plate is held in place by two pins, one at the top, and one at the bottom.


Caliber         20 mm (0.79 in.)
Weight w/accessories 104 11/16 lbs.
Weight w/o accessories 86 3/4 lbs.
Length (overall) 63 3/4 ins.
Sight radius
Principle of operation Recoil with muzzle cup
Feeding device Metal link belt type
Capacity of feeding device 100 rounds
Cooling system Air
Ammunition types A.P., H.E., Incendiary
Cyclic rate 950 r.p.m.
Type of sight Reflector
Weight of barrel 12 1/8 lbs.
Length of barrel 35.4 ins.
Length of rifling 31.5 ins.
   Twist R.H.
   No. of grooves 8
   Depth of grooves
   Width of grooves
Chamber pressure
Muzzle velocity (A.P. Shot) 2,304 f/s
         (H.E. Shell) 2,430 f/s
Effective range 600 yds.

Japanese: p. 252 (June 1, 1945)