Monday, 15 February 2016

Imperial Japanese Explosives - Army and Navy Markings and Designations

Imperial Japanese Explosives
It came to my mind that I forgot to add the descriptive information regarding IJA bombs: their designations, construction, and so on.  Thus, it will be added here alongside the Navy's version.  These also differ from the posts some time ago containing descriptions given for "Ammunition" posts.
I would also like to take this moment to apologize for this omission, and thank the readers for your continued interest.
Imperial Japanese Army Bombs
1. Designation: The Japanese Army designates 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 service 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, substitute, 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 anti-shipping bombs utilize two-piece construction; the nose and body are of one piece, and the tail cone is threaded to the body.  The special construction features of the various anti-shipping 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 gravity.
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 Japanese character for "special."
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 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 tot he extent that the white band has been omitted.  Forward of the yellow band is stenciled the type number, weight, filling, and additional description.  Aft of the suspension lug is stenciled the place and the date of manufacture and a "+" or "-" indicating a minor weight discrepancy.
Incendiary bombs with a solid filling are painted black overall with a white band forward of the suspension lug.  A symbol for incendiary bombs "ヤ" is stenciled on the bomb.
All liquid-filled bombs are painted grey overall.  A red nose tip indicates that the high-explosive 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 suspension lug and by the symbol "ヤ".
Liquid-filled smoke bombs are grey overall, have a red nose and no body band.  They are marked by the symbol for smoke "ケ".  Gas bombs are painted grey overall 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 ---- Vesicant
Brown Band ---- Blood and Nerve poison
6. Sizes: Although documents refer to 1,000kg bombs none larger than 500kg have been recovered at the time of this manual's writing
7. Fuzing: All Army bombs of 30kg and above may be fuzed in both the nose and tail.  Bombs of 250 and 500kg generally user larger weight. (Not quite sure what the book means by this)
Imperial Japanese Navy Bombs
1. Designation: Japanese Navy bombs are divided into classes: land bombs, ordinary bombs, special bombs, smoke bombs, practice bombs, target-marker bombs, training bombs, and dummy bombs.
"Land" bombs are bombs specially designed for use against land targets.  They are usually of rough construction.
"Ordinary" bombs are designed for use against ships.  They include both G.P (General Purpose) and S.A.P. (Semi Armour-Piercing) types.  They are of smoother construction than land bombs.
Special bombs are designed for various special purposes and each special class is indicated by a mark number. (See chart below)
According to a captured document, a new system of designating Navy bombs has been proposed.  The existing bombs are not to be redesignated but new bombs will be assigned mark numbers as follows:
Marks 1 through 9: Anti-shipping bombs
Marks 10 through 19: Chemically-equipped bombs
Marks 20 through 29: Anti-aircraft bombs
Marks 30 through 39: Anti-land bombs
As the name indicates, practice bombs are used for practice bombing.  Target-marker bombs are used as target marking beacons.  Dummy bombs are used for training and practice bombing.  Training bombs are used for training in handling bombs.
Smoke bombs are used for concealment purposes.
Individual bombs in these main general classes are given further designations:
a. The type number discloses the year that the bomb was adopted for service use.  In the "land" and "Ordinary" bomb classes, the first bomb of a given weight class is not assigned a type number but is merely indicated by the weight number.  Subsequent designs of the same weight are assigned type numbers.  Thus there is a No.6 land use bomb and a Type 97 No.6 land use bomb.
b. The number indicates the weight of the bomb in units of tens of kilograms.  Thus a No.6 bomb weighs 60kg, a No.25 bomb weighs 250kg, etc.  This designation is as much an indication of size as it is of weight, No.6 indicating a bomb of the 60kg size, and approximate weight.
c. A description of the bomb is indicated by the characters for land use, ordinary, etc.  If it is a special bomb, the mark number is given.
d. Model: This term has several meanings bu in this instance is used to distinguish different designs of bombs in the same general class.
e. Modification: This term represents a minor change in design or a change in filling.
2. Construction: There are two main patterns of construction of Navy bombs, typified by the "land" bombs and the "ordinary" bombs.
a. Land bombs: Land bombs are of three-piece construction.  The nose is attached to the cylindrical body either by welding and riveting or by welding alone.  The tail cone, which is filled with explosive, is attached to the body by means of a collar or coupling ring.  Either the body or tail cone is attached to the collar by welds and/or rivets and the final junction is made by attaching the other part to the collar by screws.
b. Ordinary bombs: Ordinary bombs are of two-piece construction.  The nose and body are manufactured of one piece, and are machined both inside and out.  If the tail cone is filed it is threaded into the body or, in the case of larger bombs, an interrupted screw arrangement is used to attach it to the body.  If the tail cone is the body and the cone is attached to the base plate by threads or screws.
The construction of special bombs and other general classes varies greatly and is covered in the description of each individual bomb.
3. Suspension: Bombs up to and including 250kg are suspended by a single U-shaped fixed lug.  Two lugs 180 degrees apart may be fitted to the bomb.  Larger bombs may be suspended from a torpedo-release gear by two flat guide studs located 180 degrees apart or by a suspension band fitted with the standard lug.
4. Fillings: Navy bombs are generally filled by casting the explosive directly into the case.  The cavity is protected by a thick coat of lacquer.  In some instances the explosive may be preformed into paper-wrapped sections which are usually additionally protected by a wax or a flannel coating.
5. Color and Markings: During the war the Japanese Navy has modified the color system used to differentiate its bombs.  Under both the new and old systems, the basic body color is grey: this color varies from greenish-grey to bluish-grey depending on variations in the paint and weathering conditions.  This grey paint is applied over a red anti-corrosive paint.
The old color pattern consisted of painting key colors as a broad band on the nose and tail struts.  Usually these colors were the same.  A band slightly aft of the suspension lug was an additional key.  Thin red stripes 180 degrees apart running from nose to apex of tail cone appeared on all service bombs.

In the new scheme all bombs containing explosive have the nose tipped in green.  Key color bands appear aft of the green tip and an additional key color band may appear on the tail strut.  The red stripes have been dropped.  Colored body bands are used in some instances to indicate different modifications. (See chart below)
6. Size: The largest bombs recovered are 1,500kg bombs.
7. Fuzing: As a rule, Navy bombs of 250kg and larger in weight are fitted with fuze pockets in both nose and tail.  The No.6 and No.3 sizes of land use and ordinary bombs have nose pockets only.
Next Time: Navy land and ordinary bombs

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