TM 9-1985-4; Japanese Army bombs

Japanese Explosive Ordnance – Bombs, Bomb Fuzes, Land Mines, Grenades, Firing Devices
and Sabotage Devices

Chapter 1 – Section 1

Japanese Army Bombs

1. Designation

The Japanese Army designation its bombs according to a type number, weight, and sometimes a descriptive title.

a. The type number indicates the year in which the bomb was adopted for ser-vice use.

b. The weight is expressed in kilograms and usually is stenciled on the bomb.

c. The descriptive title is not used on the standard high-explosive bombs but is used on others. The descriptive title such as smoke, incendiary, gas, subsitute, practice, and anti-shipping, indicate the purpose of the bomb.

2. Construction

The standard high-explosive bombs are of three-piece construction.On older bombs the tail cone, which is filled with explosive, is welded to the cylindrical body, and the nose section is threaded to the body. In later models the nose is welded to the body and the tail cone is threaded on.

Some of the antishipping bombs utilize two-piece construction; the nose body are of one piece, and the tail cone is threaded to the body. The special construction features of the various antishipping bombs are described under the individual bombs.

3. Suspension

All the Army bombs except those carried in containers are suspended by a single hinged rectangular lug located at the center of gravitys.

4. Filling

High-explosive bombs are usually filled with precast, paper-wrapped blocks of explosive surrounded by paraffin, or in the latest type by cast TNT. When fillings other than picric acid are used, the nature of the filling may be stenciled on the bomb. Bombs filled with an explosive other than the standard filling for that bomb are marked with the Jap cha-racter for "special".

ARMY EXPLOSIVES

Explosive		Use	Japanese Designation	Remarks
Primers (cap composition):
1.	Mercury fulminate, potassium chlorate, antimony trisulfide	Primer cap composition	Bakufun = exploding powder	Documents: Mks I and II are ammunition primers, Mk II is as fuze primer.
2.	Potassium chlorate, antomony sulfide	Primer cap composition		Most common mixture for fuze primers.
Initiators (detonators):
3.	Mercury fulminate	Initiator for fuzes and blasting caps.	Raikö = thunder mercury
4.	Lead azid	Initiator for fuzes and detonators.	Chikka Namari	Most common initiator espe- cially where a black powder realy is present.
Boosters:
5.	Picirc acid	Main booster charge	Oshokuyaku = yellow color explosive	Pressed. Toxic.
6.	Tetryl	Subbooster	Meiayaku	Pressed. Toxic.
7.	RDX	Subbooster	Shouyaku	Pressed (often with wax.)
Main charges:
8.	Picric acid	Bombs, projectiles, land mines, bangalore torpedo.	Yellow color explosive	Usually cast in performed papper-wrapped blocks. Toxic.
9.	TNT	Bombs (rare) projectiles, hand grenades.	Chakatusuyaku = tea- brown explosive	Generaly cast into case. Granualar in grenades. Toxic.
10.	TNT, 25 percent; Picric, 75 percent	Bombs	Chaoyaku = TNT-picric	Cast-rare. Documtents: TNT lowers metling point and facilitates casting. A bit less sensitive than picric. Toxic.
11.	Picric, 50 percent; Dinitronaphtalene, 50 percent.	Projectiles	Onayaku	Cast-rare. Documents: Picirc 80 percent, Dinitronaphtatha- lene 20 percent. Dinitronaph- thalene aids casting and makes less sensitive. Toxic.
12.	Picric, 90 percent; Wax, 10 percent.	Projectiles	Oshivaku = picric wax.	Pressed. Used in nose of A.P. projectiles. Documents: low sensitivity. Toxic.
13.	TNT, 70 percent; Dinitronaphatalene, 30 percent.	Projectiles	Chanayaku	Cast. Toxic.
14.	TNT, 70, 60 and 50 percent; RDX 30, 40 and 50 percent.	Bombs, projectiles, land mines, bangalore.	Nigo tanoyaku = Mk 2 pale yellow explosvie.	Cast. Appears to be the com- ing Army explosive. Many new types of ordnance have it. Toxic.
15.	Ammonium nitrate, 75 percent; RDX, 25 per-cent.	Bombs.	Anga yaku	Cast in case. White and very hygroscopic.

5. Color and markings

High-explosive bombs are painted black overall. A red band around the tip of the nose indicates that the explosive is loaded in the bomb case. A white band forward of the suspension lug indicates that the bomb case is made of high-grade steel. A yellow band forward of the white band denotes a high-explosive filling. Recently this system has been modified to the extent that the white has been omitted. Forward of the yellow band is stenciled the type number, weight, filling, and additional description. Aft of the suspen-sion lug is stenciled the place and the date of manufacture and "+" or "-" indicating a minor weight discrepancy.

Incendiary bombs with a solid filling are painted black over-all with a white band forward of the suspension lug.

A symbol for incendiary bombs " " is stenciled on the bomb.

All liquid-filled bombs are painted grey over-all. A red nose tip indicates that the high ex-plosive burster tube is loaded and a blue band aft of the nose tip indicates that the liquid filling is present.

Liquid-filled incendiary bombs are marked by a single white band just forward of the sus-pension lug and by the symbol " ".

Liquid-filled smoke bombs are gray over-all, have a red nose band and no body band. Thay are marked by the symbol for smoke " ".

Gas bombs are painted gray over-all and have a red nose band. It is supposed that color bands around the body indicate the type of gas filling. This system is utilized in marking Army gas projectiles.

Red band	Vomit gas
Blue band	Lung irritant
Green band	Tear gas
Yellow band	Vesciant
Brown band	Blood and nerve poison

6. Sizes

Although documents refer to 1,000 kg. bombs, none lager than 500-kg. has been reco-vered.

7. Fuzing

All Army bombs of 30-kg. and above may be fuzed in both the nose and tail. Bombs of 250- and 500-kg. generally use larger weight.