Monday, 13 June 2016

Imperial Japanese Explosives - Land Mines and Grenades (Part 6)

Imperial Japanese Explosives


Explosive Food Cans

Length: 4 and 1/2 inches
Diameter: 3 and 3/8 inches
Explosive: RDX (78.3%); Mineral Oil (21.7%)
Weight of explosive: 1.37 pounds
Description: Three types of explosive food cans have been recovered, whose main difference lies in the spurious food labels which conceal the true nature of the can. 

The "tin of strawberries" is typical and consists of a standard No.2 can filled with high explosive.  The tin bears a cleverly counterfeited "Libby's Strawberries" label, which covers and conceals the threaded igniter pocket in the side of the can.  This label gives the weight of the can as 1 pound 4 ounces.  The interior of the can is lined with thick brown paper.  Two rectangular metal containers filled with heavy mineral oil are placed in the main filling on either side of the igniter pocket.

Two smaller 14-ounce cans labeled "Libby's Long Slices Fancy Pineapple" and "Del Monte Mixed Salad Vegetables," which are similar to the "Strawberry" can in all respects except size and label, have been recovered.

All the types of charges can be used either as sabotage devices or booby traps depending on the type of initiating system used.  One common initiator has a scratch type igniter, a safety fuse delay (about 1 minute), and a detonator.  Another consists of a brass sleeve containing a scratch type igniter, an integral short delay train, and a detonator.  The third type of igniter consists of a brass sleeve containing a friction pull igniter, and a detonator.  This last igniter has no delay and can be used only if the charge is placed as a booby trap.

Operation: The label of the can is removed or perforated to expose the igniter pocket into which the igniter is threaded.  The activation of the igniter sets off the delay, if present, which fires the detonator and the main charge.

Metal Incendiary Cylinders

Length: 6 and 3/4 inches
Diameter: 2 and 3/4 inches
Incendiary Mixture: Thermite
Description: These cylinders are constructed of a light unidentified metal.  They are filled with thermite and have an igniter located in the center of the top section.

Four types of cylinders have been recovered which differ as to type of casings and igniters.  One casing is a plain cylinder, while the other type has vents around the top to allow more rapid escape of the thermite.  Both casings can be fitted with either a friction pull igniter or a scratch type igniter.

Both igniters are of conventional design and both employ a delay element and a 5-gram first fire charge of antimony sulphide, aluminum, and potassium chlorate.  A circular piece of wood with rough sides is provided as a scratch block for the scratch type igniter.  The block is wrapped in waxed paper and taped to the top of the cylinders in which it is used.

Operation: Place the charge and initiate the igniter.  After the delay time has expired, the first fire charge and then the main incendiary charge are ignited in turn.

Incendiary Brick

Size: Same as standard building brick

Incendiary Mixture: Potassium chlorate, sulphur, ground coal, or sugar, iron fillings, and wax
Description: This device is a skillful imitation of a standard, glazed building brick to which it is comparable in size, weight, and appearance.  The brick is wax coated with paint to give it a realistic finish and so allow it to be carried about without detection.  There is no pocket for insertion of an igniter.

Operation: The incendiary brick is ignited in various ways, all of which are alike in principle.  One method is to pour sulphuric acid and glycerine into a thin rubber tube which is weakened at one point to allow the acid to burn through quickly.  When the acid burns through the tube, it drips onto a small amount of potassium permangenate which ignites the brick.

Incendiary Soap

Length: 4.17 inches
Width: 2.67 inches
Thickness: 1.45 inches
Weight: 14 ounces

Incendiary mixture:
-Barium Nitrate: 30.4%
-Paraffin: 19.4%
-Magnesium: 11.3%
-Aluminum: 11.1%
-Rosin: 10.9%
-Ferrosoferric Oxide: 9.1%
-Nitrocellulose: 4.4%
-Gritty Siliceous Material: 2.6%

Description: This incendiary bar is specifically designed to resemble a bar of "Ivory" soap.  The word "Ivory" is stamped on one side and "Proctor and Gamble" on the other.  The bar burns with an intense flame, but is easily extinguished by water.  It is difficult to ignite.

No method of ignition has been found, but it is probable that some type of ignition device is inserted into the recess in the side of the bar.

40mm Hollow-Charge Rifle Grenade

Overall length: 7.98 inches
Maximum diameter: 1.58 inches

Color: Black and grey

Total weight: 12.45 ounces
Filling: 50/50 RDX and TNT
Weight of filling: 3.81 ounces
Description:  This grenade is a copy of the German Gross Gewehr Panzergranate and is fired from a cup launcher attached to the standard 6.5mm rifle.

The body is cylindrical with a semiconical shaped head.  It is made in two parts threaded together and fitted with a ballistic cap and cone to give the hollow-charge effect.  The forward part contains the explosive charge cast around the cone.  The after part which is made of aluminum has a rifled collar near the base and contains the fuze and explosive train.
The fuze is held in by a base plate with a protruding spigot which is screwed into the base of the grenade.  The fuze is held in position by the spigot.  The needle firing pin is secured in a housing that has a four stirrup-like springs protruding from the side.  Around the housing is a setback spring held in by an arming sleeve which has two sets of grooves notched on the inner side. 

Holding the firing pin stationary is a coil clock spring which is held in by the arming sleeve.  There is also a creep spring between the firing pin and detonator.   The propelling charge consists of a special cartridge with a wooden bullet.
Operation: On firing, setback causes the arming sleeve to move down and it is held down by the stirrup springs which engage in the groove in the arming sleeve.  Centrifugal force then causes the clock spring to expand and the fuze is armed.  On impact the firing pin housing overcomes the creep spring and moves onto the flash cap setting off the detonator and booster.

30mm Hollow-Charge Rifle Grenade

Overall Length: 8 inches
Maximum Diameter: 1 and 5/8 inches

Color: Black and grey

Total Weight: 8.25 ounces
Filling: 50/50 RDX and TNT
Weight of Filling: 1.75 ounces

Description: The explosive head of the 30mm is of the same type construction as that of the 40mm, but on a smaller scale.  The spigots of the 30 and 40mm grenades are identical with the exception of the threads on their forward ends.  Both grenades use the same fuze.

Operation: The operation of the 30mm hollow-charge rifle grenade is identical to that of the 40mm size.

Model 3 Modification 1 Rifle Grenade

Overall Length: 8 inches
Maximum Diameter: 1 and 5/8 inches
Thickness of body wall: 1/8 inch
Length of body: 2 and 13/16 inches
Length of tail: 4 and 5/16 inches
Length of fuze: 1 and 3/16 inches

Color: Black

Filling (main charge): TNT
Weight of Filling: 3 ounces

Description:  This grenade is similar to the Type 99 Kiska grenade with a tail assembly added.  It is designed t be fired from the spigot type rifle grenade launcher.  The body and tail are painted black.

The grenade body is a smooth-surfaced, cylindrical cast steel tube.  It is threaded internally at the forward end to receive the cover plate.  There is a bored opening in the base of the grenade body.  A cylindrical solid steel plug, threaded on its after end to receive the tail assembly, is pressed into this hole.

The tail assembly consists of a stabilizer tube to which four fins are welded.  The tube is constructed of rolled sheet steel with a smooth weld down the joining seam.  Threads are pressed into the forward end to correspond with those on the base plug.  The four fins are of light metal.  The outer end of each fin is doubled back to provide a smooth exposed surface.  The inner edge is bent 90 degrees and provides a surface for spot welding the fin to the tube.  The fins are positioned at 90 degree intervals around the circumference of the tube.

The fuze body differs from the Type 91 and Type 97 hand grenade fuzes only in having an aluminum striker block into which is screwed a steel striker.  A brass shear wire through the block holds the striker away from the percussion cap.

The explosive train of the grenade consists of a percussion cap, black powder relay, cyclonite primer, tetryl booster and a main charge of cast TNT.  The cyclonite is enclosed in a brass container, the tetryl in a cardboard cylinder.  Directly under the tetryl booster there is a setback buffer consisting of a felt washer and a jelly-like pellet.

Operation: Prior to firing the grenade from the rifle the safety fork is withdrawn.  The fuze is fully armed.  On impact the brass wire through the striker block is sheared and the steel striker is driven into the percussion cap.  The resultant flash ignites the black powder relay.

The fuze is instantaneous and cannot be substituted as a fuze for hand grenades.

Remarks: A translation of the labels attached to the stabilizer tube gives the following information: "This grenade can be used on rifles Type 38 and Type 99.  The wooden bullet for Type 38 and Type 99 is to be used."  These two rifles are the standard combat weapons for Japanese troops.

A translation of the tag attached to the safety fork gives the following precautionary measures: "Do not remove fork until ready to fire." and "Do not drop or otherwise strike on the nose."

Smoke Rifle Grenade

Overall Length: 8 and 1/2 inches
Maximum Diameter:
-Body: 2 inches
-Fins: 2 and 9/16 inches

Color: Silver

Total weight: 1.29 pounds
-Hexachlorethane: 56.2%
-Zinc: 27.6%
-Zinc chloride: 2.9%
-Zinc oxide: 13.4%

(The above numbers total 100.1%.  I don't know why.)

Description:  This grenade is used with a special adapter which fits over the end of the rifle barrel.  It is painted silver and thoroughly waterproofed with coats of heavy lacquer and paraffin.

The nose is of No.23 gage B. and X. tin plate with rolled threads to fit those on the body of the grenade.  Soft iron wire is wrapped in the thread groove and soldered in place, presumably to aid in sealing the joint.  The body proper is rolled from No.23 gage B. and X. tin plate and is soldered along one longitudinal seam.  Rolled threads are provided at each end to fit the threads on the nose and base.

The base is stamped from No.18 gage B. and S. sheet steel and is screwed onto the body by means of rolled thread.  Soft iron wire is wrapped and soldered into these thread grooves.  The base is partially filled with plastic which has a threaded hole half filled with solder.  The bottom plate is held in place by a small screw imbedded in the solder.  The igniter pellet is encased in a thin walled brass container which is supported by tin plate screwed and soldered onto the body.

The four smoke ports are placed at 90 degree intervals around the base and are covered with light sheet metal discs which are held in place by waterproof cement covered with paraffin.  There are three flash ports, spaced at 120 degree intervals, in the bottom of the base.

The grenade tube is made of No.18 gage B. and S. seamless steel tubing and the upper end is threaded to fit the small end of the base.  The threaded joint is wrapped with adhesive tape.  The tube is sealed with a paraffin impregnated cardboard disc attached to 9 inches of heavy twine.  The four fins are soldered to, and are equally spaced around, the tube and are of No.24 B. and X. tin plate.

The motive force and primary ignition are furnished by a standard .256 caliber Japanese rifle cartridge loaded with 1.927 grams of powder and fitted with a wood pellet.  This cartridge is wrapped in paper and stored in the grenade tube.

Operation: The rifle cartridge is removed from the grenade tube and inserted into the rifle.  The grenade is placed over the spigot adapter.  When the rifle is fired, the gases from the cartridge propel the grenade and also pass through the flash ports to initiate the igniter pellet which in turn ignites the smoke mixture.  Smoke is then emitted through the emission holes.

Small Incendiary Rifle Grenade

Overall Length: 10 inches
Maximum Diameter: 1 and 7/8 inches

Color: Grey with purple body band

Total weight: 1.01 pounds
Filling: White Phosphorus
Weight of Filling: 42 ounces (Manual states 42 pounds!)
Delay: 4-5 seconds

Description:  This grenade is designed to be launched from a spigot type rifle grenade launcher on the Type 38 or Type 99 Japanese rifle, using a cartridge having a wooden bullet.

The grenade is of light, seamless, steel construction and has an incendiary filling of white phosphorus.  The nose piece is threaded at its forward end to receive the fuze.  A thin, metal well extends into the filler and is soldered around the fuze pocket to give an air tight seal.  This well contains the detonator and auxiliary detonator of the fuze, which serves as the bursting charge for the grenade.

The barrel of the grenade is threaded at its forward end to take the nose piece, and at its after end to receive the hemispherical end plate internally and the base piece externally.  The end plate has a small hole in its center.  The base piece is threaded at one end to screw onto the barrel and at the other end to screw into the stabilizer tube.  A bakelite cushion is cast into the base piece to fit the hemispherical end plate.

The stabilizer consists of a cylindrical tube which threads onto the base piece.  Four fins are welded to the after section of this tube at 90 degree intervals.  The rolled threads, joining the barrel and base piece and base piece and stabilizer, are reinforced by wrapping and soldering soft iron wire into the thread grooves.

The fuze used in this grenade is the same as that used in the Type 97 hand grenade.

Operation:  After the grenade has been placed over the spigot adapter of a rifle loaded with a cartridge having a wooden bullet, the safety pin is removed from the grenade.  When the rifle is fired, the gases from the cartridge propel the grenade, and the force of setback initiates the grenade fuze.  After a short delay, the fuze detonates, rupturing the case of the grenade.

Next Time: Italian and French Explosives

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