Monday, 13 July 2015

Imperial Japanese Army Ammunition: IJA Rockets, Mortars and Explosive Charges

Japanese Explosive Ordnance: Army and Navy Ammunition

20cm High Explosive Spin-Stabilized Rocket

Assembled Round:
-Weight of complete round: 84.51kg
-Length of complete round (with fuze): 38.58 inches
-Weight of filled head (w/o fuze): 39.2kg
-Weight of filling (cast TNT): 16.2kg
-Length of head (w/o fuze): 17.52 inches
-Diameter of head: 7.87 inches
Filling: Cast TNT - 16.2kg

-Army Type 100 mortar fuze - Selective: Instantaneous, short delay

-Weight of filled motor: 45.31kg
-Weight of propellant: 9.52kg
-Length of motor: 19.06 inches
-Diameter of bearing surface: 7.99 inches

-Type: Smokeless powder B
-Weight: 9.52kg
-Number of sticks: 6 long, 2 short
-Smokeless powder B by analysis is a mixture of 27.71% N.G., 63.50% nitro-cellulose, 0.45% graphite, 0.34% percent ash, 3.81% ethylcentralite, 3.68% diphenyl formamide, and 1.30% volatiles. Six long sticks (34cm x 5.8cm x 1.05cm perforation) and two short sticks same diameter and perforation and 1/2 length. In some cases, one or both of the short grains have been omitted in assembly.

Ignition Mechanism:
-Igniter: Pull friction igniter
-Ignition charge (B/P/ in two blue lacquered silk bags)
-Weight of ignition charge: 0.04kg

Color and Markings:
Black overall, Head carries single yellow band at its junction with rocket motor. Weight of head and motor stenciled on each component.

The only launcher recovered for use with this round is a single barrel-type launcher

A newer model of this round has been recovered, similar to the first but with the rocket motor wall diametrically reduced to 18.9cm, giving a bourrelet effect at each end of the motor. The motor weight is correspondingly reduced to 42.43kg. Neither the head nor the motor is interchangeably with its respective component in the older round.

Type 89 58mm H.E. Mortar

Weight of complete round: 1.6 lbs
Weight of main charge: 5.4 oz
Explosive Components:
-Main charge: TNT
-Propellant: Nitrocellulose diphenylamine flaked powder.
Overall length: (w/o fuze): 4.33 inches
Maximum diameter: 50mm

1. Black overall with red band at nose, and
-A. A yellow band below the bourrelet and white band forward of rotating band
-B. Yellow band midway on the shell
2.Maroon color overall for Navy use
3.Green nose, black body with yellow and white bands.

-Type 88 small instantaneous fuze

Used in:
-Type 89 grenade discharge

The body of this shell is made of three parts.
-The propellant base housing houses the propellant container and the percussion primer.
-The main shell base cover is threaded to the top section on one end and to the propellant housing on the other.
-The top section has an opening in the top to receive the fuze.
On firing, the gases generated blow through the ports in the base housing, expanding the copper rotating into the rifling of the discharger giving a gas seal and imparting rotating to the seal.

The Navy version of this shell is exactly the same in construction as the Army version the only variation being in the color scheme, Two minor variations of construction have been found.
1. The nose portion screws on (LH) the body directly below the bourrelet. The base is solid instead of being closed with base plate.
2. Similar to the first variation except the threads are right hand (RH).

I believe this entry is a typo and should read 50mm rather than 58mm

Type 95 50mm Smoke Mortar

Weight of complete round: 1.9 lbs
Weight of smoke filling: 3.7 oz
-Smoke compound: Hexachlorethane smoke mixture
-Propellant: Nitrocellulose diphenylamine flaked powder.
Overall length (w/o fuze): 4.33 inches
Maximum diameter: 50mm

Black overall with a red band at the nose and two white bands, one immediately below the bourrelet and the other before the rotating band.

-Type 89 small time fuze

Used in:
-Type 89 grenade discharger

The projectile casing is of forged steel. The nose screws onto the main body at a point just behind the bourrelet. The main body is joined to the base with a press-fit held by four screw shear pins. The propellant base housing which screws onto the shell base is similar in construction and operation to that of the H.E. shell. The smoke mixture is held in a brass can inside the main body and has attached to it by a short cord a steel retarder cup to slow its decent.

When the fuze gaine fires, it ruptures the thin plate in the base of the gaine, ignites the smoke mixture, and expels the smoke candle from the shell casing.

Type 89 50mm Incendiary Mortar

Weight of complete round: 1.25 lbs
Weight of incendiary mixture: 10.7 oz
Filling: Incendiary Mixture:
-Potassium nitrate: 47.7%
-Aluminium: 21.7%
-Antimony trisulphide: 6.1%
-Wax: 2.8%
Propellant: Nitrocellulose powder
Overall length: 6.25 inches
Length of propellant containers: 1.25 inches
Diameter propellant container: 1.02 inches
Maximum diameter: 50mm

Natural brass body with black propellant container

Powder delay train

Used in:
-Type 89 grenade discharger

The shell is a cylindrical sheet metal tube with a hemispherical nose and is covered with clear lacquer. Around the side of the casing are four silver-foil disks, each disc covering seven ports in the shell casing. The casing is crimped over the base, which contain two black powder delay trains and is threaded to receive the propelleant housing. The propellant housing is of steel with six gas escape ports in the sides and a percussion cap set in the screwed in base. The propellant is contained in a copper cup inside the propellant housing.

The flash from the propellant ignites the delay trains in the base of the shell, which in turn ignite the incendiary filling.

Another incendiary shell, the Type 10 year, is similar in appearance and operation to the Type 89 shell. It is 5 and 7/8 inches in length; the color of the body is natural brass; and the propellant assembly is black. There are eight sets of perforations covered with silver-foil disks. The Type 10 year shell is fired from the Type 10 year grenade discharger, an obsolete weapon that was the forerunner of the Type 89 grenade discharger.

50mm Finned Bangalore Torpedo

I'm unsure if this is a printing error or if there is no visual documentation of the item.

Weight of complete round: 8.11kg
Weight of main charge: 2.87kg
Main charge: Picric
Overall length (w/o fuze): 78.37 inches
Base section length: 33.25 inches
Length from after end of base to forward bearing surface of base section: 12.75 inches
Maximum diameter of explosion tube: 50mm

-Length: 14.75 inches
-Maximum width: 3.5 inches
-Minimum width: 2.5 inches

Fins and bangalore section are painted tan with a red band at the top of each section. The modified portion of the base section is painted black.

-Instantaneous delay fuze for bagalore mortar

Used in:
-Type 98 discharger

The projectile is constructed in two sections. The nose section is a standard bangalore length, while the base section is a bangalore length cut off and modified to fit into the barrel of the discharger. This section also has three spot-welded brackets to which the sheet metal fins are bolted. A cap, having two circumferential grooves cut into it to divide the surface into three after bearing surfaces, is welded around the after end of the base section. A length of 50mm tubing is welded to the base section and serves as a forward bearing surface for the projectile. A plate is welded to the bangalore base section to prevent the bangalore from sliding too far down into the launcher tube.

50mm Stick Charges

(SM) Small (LA) Large
Weight of complete round: (SM) 15.62 lbs - (LA) 17 lbs
Weight of main charge: (SM) 7 lbs - (LA) 10 lbs
Explosive components:
-Main charge: (SM) Picric - (LA) Picric
-Propellant: (SM) Black Powder - (LA) Black Powder
Overall length: (SM) 27.35 inches - (LA) 25.5 inches
Length of explosive container: (SM) 6.75 inches - (LA) 4.5 inches
Width of explosive container: (SM) 4.5 inches - (LA) 6.25 inches
Height of explosive container: (SM) 4.5 inches - (LA) 6.25 inches
Wall thickness: (SM) 0.05 inches - (LA) 0.25 inches
Diameter of stick: (SM) 50mm - (LA) 50mm

The metal explosive container is painted black, while the wooden "stick" is left unpainted. The large model has a white stripe fore and aft around the explosive box.

Used in:
Type 98 discharger

Two pull igniters

The projectile consists of a cast iron box containing blocks of picric acid mounted on a wooden pole 50mm in diameter. Two pull igniters are inserted in the bursting charge and are tied to metal loops on each side of the launcher tube collar. When the projectile is fired these pull igniters are initiated and will in turn set off the bursting charge after a short delay. The black powder propellant in silk bags is placed in the launcher tub below and independently of the projectile. The propellant is fired by a pull igniter inserted in the ignition aperture in the side of the launcher tube.

Next time: 70mm Mortar rounds, including the interesting High Explosive Anti-Aircraft Barrage Mortar Projectile 

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