Imperial Japanese Explosives
Type 99 Hand Grenade
Overall length: 3 and 1/2 inches
Maximum diameter: 1 and 5/8 inches
Total weight: 0.8 pounds
Filling: Cast picric acid
Delay: 4-5 seconds
Color and markings: Body is black with white label pasted around it. The top of the grenade is painted red; fuze cover, red; fuze, brass.
Maximum diameter: 1 and 5/8 inches
Total weight: 0.8 pounds
Filling: Cast picric acid
Delay: 4-5 seconds
Color and markings: Body is black with white label pasted around it. The top of the grenade is painted red; fuze cover, red; fuze, brass.
Description: The cast steel body has smooth surfaces. There is a shoulder projecting 1/16 inch from each end of the body. The inside of the body is finished with lacquer to keep the filler from reacting with the steel case. The filler is also wrapped in heavy paper.
A light metal flash deflector is fitted in the top of the grenade. This deflector is 3/8 inch wide and 7/8 inch in diameter. Two 1/8 inch holes are punched in the outer periphery and match the spanner holes in the fuze body. This positions the gas vents in the fuze 90 degrees from the holes in the flash deflector. The flash deflector reduces the possibility of the flash from the cap burning the hand of the thrower and the possibility of the flash being seen by the enemy at night.
The fuze is similar to that used in the Type 91 and Type 97 grenades with a few improvements. On the old type the striker may turn or spring clear of the grenade when the safety wire is pulled. In this fuze, a screw in the fuze body projects through a slot in the striker cover and keeps the cover in place. The slot allows the cover to move down when the striker is struck on a hard object. Also, the striker and inertia weight are machined together and the striker protrudes so that it does not have to be threaded down to arm the grenade. In other respects, the fuzes are identical.
Operation: The safety pin is withdrawn and the head of the fuze is truck on some hard object. This forces the striker down into the primer igniting the delay.
Remarks: A Type 99 grenade has been encountered with a machined, waterproof, metal fuze cover. The only difference between this variation and the standard grenade is the fact that the flash guard is externally threaded to receive the waterproof fuze cover.
Type 4 Pottery Hand Grenade
Height (base to top of neck): 4 inches
Diameter: 3 inches
Body (material): Terra Cotta
Thickness of case: 7/16 inch
Total weight of grenade: 16 ounces
Filling: Type 88 explosive
Delay: 4-5 seconds
Color and markings: Light brown
Diameter: 3 inches
Body (material): Terra Cotta
Thickness of case: 7/16 inch
Total weight of grenade: 16 ounces
Filling: Type 88 explosive
Delay: 4-5 seconds
Color and markings: Light brown
Description: Except for the neck at the top, the grenade is spherical, consisting of two hemispheres baked together. The pottery body is light brown in color, lightly glazed inside and out. The grenade is encased in a straw-coloured rubber sack which serves as waterproofing and permits the thrower to take a better grip.
The ignition system consists of a match composition, a 4 or 5 second delay element, a lead azide initiator, and a tetryl booster. All but the match composition are encased in a rubber tub which is lacquered into the neck of the grenade. The upper portion of the delay element is surrounded by a wooden collar, the top of which is covered with the match composition.
A wooden scratch block is seated on top of the neck of the grenade. It is held in place by a small rubber sack which snaps around the neck of the grenade. This sack serves a second purpose in waterproofing the ignition system.
A cloth band tied around the neck is probably used for carrying.
Operation: The small rubber sack is removed from the top and the scratch block is struck on the protruding match composition, igniting the delay element. The grenade is thrown and explodes after a 4 or 5 second delay.
Remarks: This grenade appears to be made of the same type pottery as the Type 3 pottery land mine, and like the land mine, uses Type 88 explosive. For these reasons it may be assumed to be a Navy weapon.
The color of the grenade may vary from white to dark brown, and the exterior may be glazed or unglazed.
The ignition system consists of a match composition, a 4 or 5 second delay element, a lead azide initiator, and a tetryl booster. All but the match composition are encased in a rubber tub which is lacquered into the neck of the grenade. The upper portion of the delay element is surrounded by a wooden collar, the top of which is covered with the match composition.
A wooden scratch block is seated on top of the neck of the grenade. It is held in place by a small rubber sack which snaps around the neck of the grenade. This sack serves a second purpose in waterproofing the ignition system.
A cloth band tied around the neck is probably used for carrying.
Operation: The small rubber sack is removed from the top and the scratch block is struck on the protruding match composition, igniting the delay element. The grenade is thrown and explodes after a 4 or 5 second delay.
Remarks: This grenade appears to be made of the same type pottery as the Type 3 pottery land mine, and like the land mine, uses Type 88 explosive. For these reasons it may be assumed to be a Navy weapon.
The color of the grenade may vary from white to dark brown, and the exterior may be glazed or unglazed.
Type 23 Hand Grenade
Overall length: 3 and 3/4 inches
Maximum diameter: 2 inches
Total weight of grenade: 1 pound
Filling: Granular TNT
Weight of filling: 39.5 grams
Delay: 5 and 1/2 seconds
Color and markings: Black
Maximum diameter: 2 inches
Total weight of grenade: 1 pound
Filling: Granular TNT
Weight of filling: 39.5 grams
Delay: 5 and 1/2 seconds
Color and markings: Black
Description: The body, unlike the Type 91 or Type 97, has no longitudinal serrations, but does have five transverse depressions. On one side, fitted top and bottom, are two rings which could be used for carrying or for anchoring. The lead cover is screwed on to the top of the grenade and is grooved to provide a grip for easy removal. The thumb cover release holds the cover on and must be depressed before the cover can be removed.
When this is depressed, the cover can be unscrewed in one and one-half turns, thus exposing the firing string which is attached to a friction igniter.
Operation: The thumb cover release must be depressed, and then the cover must be removed. When the firing string is pulled, it draws a sanded string through a match composition. The ignition of the match composition will ignite the black powder delay train.
Type 98 Stick Grenade
Maximum diameter: 1 and 5/16 inches
Total Weight: 1 pound, 3 ounces
Filling: Cast picric acid
Weight of filling: 3 ounces
Delay: 4-5 seconds
Color: Black body; Unpainted handle
Description: The body is cylindrical in shape and is made of cast steel 1/4-inch thick. The handle is turned from soft wood and slips into the steel body where it is held by three screws. This joint is sealed with a coating of tar. The screw cap at the pull end of the handle is of light, tin-plated steel.
The fuze consists of a friction ignition composition with a sanded string running through it. This string extends up the hollow handle and is connected to a pull ring which is exposed by removing the screw cap at the top of the handle.
Operation: The screw cap is removed from the top of the handle. The ring inside the handle is then pulled. This draws the sanded string through the ignition composition igniting the 4 or 5 second delay. The delay train detonates a cap which detonates the main charge.
This grenade has more fragmentation effect than the German high explosive stick grenade.
Type 3 Conical Antitank Hand Grenade
Small Grenade
Length of grenade: 5 and 7/8 inches
Length of tail: 14 inches
Diameter at base: 4 inches
Length of fuze: 1 and 7/8 inches
Length of cone: 2 and 3/8 inches
Diameter of cone: 2 inches
Cone angle, apex: 38 degrees
Total weight: 0.84 kg
Thickness of cone: 3 mm
Material of cone: Aluminum
Large Grenade
Length of grenade: 6 and 3/4 inches
Length of tail: 14 inches
Diameter at base: 4 and 3/8 inches
Length of fuze: 1 and 7/8 inches
Length of cone: 3 and 3/4 inches
Diameter of cone: 2 and 3/8 inches
Cone angle, apex: 30 degrees
Total weight: 1.25 kg
Thickness of cone: 3 mm
Material of cone: Steel
Description: This grenade is manufactured in two sizes. The basic principles of construction are the same in both sizes, but variations occur in weights, measurements and the explosive charge. The grenade consists of a cone-shaped explosive charge, a metal cone, and a wooden base all contained in a silk bag. A fuze is inserted and a tail attached to the apex of the charge.
The explosive charge is cast in the form of a truncated cone. A metal cone is inserted in the base and in the upper end is a well which receives the gaine of the fuze. Surrounding the gaine is a cast ring pellet. In the large size grenade the explosive is Type 94, and in the small size grenade it is Pentolite (50/50 TNT and PETN). A thin layer of waxed paper surrounds the charge.
At the bottom of the explosive charge is a wooden base which is flat on the top and rounded on the bottom. The hole in the base has a slightly smaller diameter than the hole in the cone.
Covering the charge and base is a silk bag either white or olive drab in color. When the grenade is assembled, a drawstring closes the bottom. A metal ring is inserted over the top of the bag. Inside the top of the explosive charge is fitted an adapter ring which is threaded to receive the fuze. Four screws hold the parts together.
Tied around the top of the grenade is a tail made of hemp to provide stability in flight and to make the grenade strike the tank base first. The fuze is constructed in two parts which are threaded together. The lower body has external threads for screwing into the adapter ring and internal threads for receiving the gaine. The striker is held in position by a safety pin and creep spring. The under side of the upper body and the top of the striker are curved so that if the grenade strikes at a slight angle the striker will be cammed down.
The explosive charge is cast in the form of a truncated cone. A metal cone is inserted in the base and in the upper end is a well which receives the gaine of the fuze. Surrounding the gaine is a cast ring pellet. In the large size grenade the explosive is Type 94, and in the small size grenade it is Pentolite (50/50 TNT and PETN). A thin layer of waxed paper surrounds the charge.
At the bottom of the explosive charge is a wooden base which is flat on the top and rounded on the bottom. The hole in the base has a slightly smaller diameter than the hole in the cone.
Covering the charge and base is a silk bag either white or olive drab in color. When the grenade is assembled, a drawstring closes the bottom. A metal ring is inserted over the top of the bag. Inside the top of the explosive charge is fitted an adapter ring which is threaded to receive the fuze. Four screws hold the parts together.
Tied around the top of the grenade is a tail made of hemp to provide stability in flight and to make the grenade strike the tank base first. The fuze is constructed in two parts which are threaded together. The lower body has external threads for screwing into the adapter ring and internal threads for receiving the gaine. The striker is held in position by a safety pin and creep spring. The under side of the upper body and the top of the striker are curved so that if the grenade strikes at a slight angle the striker will be cammed down.
Operation: Before the grenade is thrown the safety pin is pulled out. On impact the firing pine overcomes the spring and moves down to pierce the primer. The fuze is not "all-ways action", but will probably function on a slight angle of impact.
A second small grenade has been recovered which is identical to the previously described small grenade in measurements and type of construction but differs in the following details. The silk bag which covers the charge of the second grenade is made of bright yellow finished silk. The main explosive charge is picric acid with a small RDX booster. The adapter ring is bakelite instead of metal, while a straw tail is used in place of hemp.
The fuze of the second grenade has a black finish, a single safety pin, and a gaine which is crimped to the fuze body, but otherwise is similar in construction and operation to the fuze of the first grenade.
A second small grenade has been recovered which is identical to the previously described small grenade in measurements and type of construction but differs in the following details. The silk bag which covers the charge of the second grenade is made of bright yellow finished silk. The main explosive charge is picric acid with a small RDX booster. The adapter ring is bakelite instead of metal, while a straw tail is used in place of hemp.
The fuze of the second grenade has a black finish, a single safety pin, and a gaine which is crimped to the fuze body, but otherwise is similar in construction and operation to the fuze of the first grenade.
Sling Hand Grenade
Maximum diameter: 1 and 13/16 inches
Total Weight: 1 pound, 3 ounces
Filling: TNT
Weight of filling: 1 ounce
Delay: 4 or 5 seconds
Color: Black
Description: The sling grenade consists of a steel grenade body, wooden base plug, reinforcing cloth, scratch type friction ignited fuze, wooden fuze seat, wooden spacing ring, and a metal protective cap.
The rough, cast steel, cylindrical grenade body has a hollow projection on its forward end into which the wooden fuze seat and fuze are fitted and secured with glue. The after end of the body opens directly into the TNT filled explosive cavity of the grenade. This opening is closed by the wooden base plug, which is glued in place. The throwing line is attached to the after end of the wooden base plug.
A strip of reinforcing cloth is wrapped around the base plug and the after end of the grenade body in order to help prevent the two sections from pulling apart when a line is used to throw the grenade. The cloth is lashed securely in place by light line, which is tied around the annular groove in the grenade body and the cylindrical after section of the base plug.
A light, sheet metal cap is sealed over the nose of the grenade with waterproof paper tape. The wooden spacing ring prevents contact between the fuze and the protective cap. A flat surface on the side of the ring is coated with the abrasive compound used to ignite the fuze.
The fuze for the sling grenade is made in two sections: a long brass detonator tube and a short igniter head. This tube is pierced by a single gas port and is crimped to the detonator tube.
Operation: The abrasive on the spacing ring is rubbed against the match head of the fuze to ignite the match composition which initiates the firing train. The grenade is then thrown by hand or by means of the line attached to the ring in its base. The delay is from 4 to 5 seconds.
1/2kg Incendiary Hand or Mortar Grenade
Maximum diameter: 2 inches
Body material: Brass
Weight: 1.1 pounds
Filling: White Phosphorus
Delay: 4 or 5 seconds
Description: This grenade may be thrown by hand or projected with the 50mm grenade discharger, Model 89. The incendiary filling is contained in a brass body which may have a propelling charge on the base. The fuze is identical to the one used in the Type 91 and Type 97 fragmentation hand grenades.
The steel propellant container is 1 and 1/4 inches long, 1.02 inches in diameter, and has six perforations in its walls. It is screwed into the base of the body. A perforated plug screws into the base of this container and in a cavity in this is a percussion cap. Two flash holes head through the percussion cap holder to a small quantity of black powder. A perforated steel disc covers the plug and inside the propellant container proper is a copper cup containing flakes of nitrocellulose propellant powder.
Operation: The firing pin must first be threaded down into the inertia weight. The safety pin must then be withdrawn. If the grenade is to be thrown by hand, it is necessary to strike the inertia weight on some hard object thus driving the firing pin into the primer to ignite the delay train.
If the grenade is to be fired from the grenade discharger, or knee mortar as it is sometimes called, the grenade with propellant container is dropped base first into the discharger. When the trigger mechanism of the discharger is operated, its firing pin strikes the percussion cap igniting the propelling charge which propels the grenade. Force of setback causes the firing pin in the grenade fuze to compress the creep spring and hit the primer to ignite the delay train.
Next Time: More Imperial Japanese Grenades, and Sabotage Devices
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