Imperial Japanese Navy Explosives
Type 2 No.6 Mk 21 Bomb Model 1
Fuzes: D-4(a)
Overall Length: 41 inches
Length of body: 38 inches (w/ nose piece)
Diameter of body: 9 and 1/2 inches
Thickness of wall: 1/16 inches
Material of wall: Steel
Type of suspension: Horizontal
Suspension lug: Normal Navy type suspension lug
Dimensions of tail struts: None
Material of tail: Sheet Steel
Type of filling: 40 1kg high-explosive hollow-charge bombs
Weight of filling: 88 pounds
Total weight of bomb: 132 pounds
Charge/weight ratio: 66%
Color and markings: Gary overall. One inch green band on nose. Brown band just aft of green band. Two 1/2-inch white bands on body marking the position of binding straps.
Description: The canister consists of a blunt-nose assembly and a light tail piece, around which are fitted three steel segments held together by two circumferential metal retaining bands. Two steel wires, which are attached to the nose, run longitudinally along the canister and pass through the buckles of the bands locking them together.
The buckles open automatically when the wires are withdrawn. The nose assembly is constructed of two pieces held together by four lead sealing strips. The forward piece is hollow and has a fuze pocket. The after piece contains a wooden disk. Set off center in the disk is a flat, round can housing a black powder burster charge in an annular silk bag.
The eccentric position of the charge centers the ignition hole of the can directly under the fuze and places the main portion of the charge near to the point at which the two steel release wires are attached to the nosepiece. This accounts for a more direct pull being exerted on the release wires when the burster charge detonates.
Operation: Upon release from the plane the aerial burst fuze functions. The burster charge is fired. shearing the lead sealing strips and blowing off the forward nosepiece. The nosepiece withdraws the release wires from the buckles of the retaining bands which frees the segments of the canister. The 1-kilogram bombs separate and fall individually.
The buckles open automatically when the wires are withdrawn. The nose assembly is constructed of two pieces held together by four lead sealing strips. The forward piece is hollow and has a fuze pocket. The after piece contains a wooden disk. Set off center in the disk is a flat, round can housing a black powder burster charge in an annular silk bag.
The eccentric position of the charge centers the ignition hole of the can directly under the fuze and places the main portion of the charge near to the point at which the two steel release wires are attached to the nosepiece. This accounts for a more direct pull being exerted on the release wires when the burster charge detonates.
Operation: Upon release from the plane the aerial burst fuze functions. The burster charge is fired. shearing the lead sealing strips and blowing off the forward nosepiece. The nosepiece withdraws the release wires from the buckles of the retaining bands which frees the segments of the canister. The 1-kilogram bombs separate and fall individually.
1-kg Hollow Charge Bomb
Fuzes: B-5(b)
Overall Length: 17 and 1/2 inches
Length of body: 8 and 1/2 inches
Diameter of body: 1 and 3/4 inches
Thickness of wall: 1/16 inches
Material of wall: Steel
Type of suspension: Carried in clusters of 40 in a container
Suspension lug: None
Suspension lug: None
Length of tail: 9 inches (w/ fuze)
Width of tail: 1 and 3/4 inches
Dimensions of tail struts:
-Length: 1 and 3/8 inches
-Diameter: 1 and 3/4 inches
-Diameter: 1 and 3/4 inches
-Thickness: 1/32 inch
Material of tail: Light Sheet Tin
Type of filling: Type 98 explosive and Tetryl booster
-TNT: 70%
-HND: 30%
-TNT: 70%
-HND: 30%
Weight of filling: 11 ounces
Total weight of bomb: 2 pounds 3 ounces (excluding nosepiece)
Weight of tail assembly: 10 ounces
Weight of tail assembly: 10 ounces
Charge/weight ratio: 31%
Color and markings: Body is a natural steel color. The tail assembly is aluminum colored.
Construction of body: The body is constructed of tubular steel. An aluminum nose cap and hollow metal cone are crimped into the nose. The fuze and tail assembly are threaded into the base of the body.
Construction of tail: Four fins are soldered to the tail cone and braced at the after end by a circular strut. The tail cone is secured to the fuze body by a four small screws.
The arming system consists of arming vanes at the after end of the tail connected to the inertia weight by a threaded reach rod which passes through the tail cone. A spring-loaded safety detent which fits into the inertia weight is located on the side of the tail cone and is held in the safe position by an arming vane.
A thin metal disk attaching to the arming wire is placed on top of the arming vanes. It prevents the vanes from rotating and acts as a drogue to withdraw the arming wire when the bomb is released.
Operation: When the bomb is released from the canister the pressure of the air on the drogue forces it from the bomb thereby withdrawing the arming wire. The safety detent spring ejects the reach rod from the inertia weight. The inertia weight and striker are then free to move forward on impact and hit the primer.
Construction of tail: Four fins are soldered to the tail cone and braced at the after end by a circular strut. The tail cone is secured to the fuze body by a four small screws.
The arming system consists of arming vanes at the after end of the tail connected to the inertia weight by a threaded reach rod which passes through the tail cone. A spring-loaded safety detent which fits into the inertia weight is located on the side of the tail cone and is held in the safe position by an arming vane.
A thin metal disk attaching to the arming wire is placed on top of the arming vanes. It prevents the vanes from rotating and acts as a drogue to withdraw the arming wire when the bomb is released.
Operation: When the bomb is released from the canister the pressure of the air on the drogue forces it from the bomb thereby withdrawing the arming wire. The safety detent spring ejects the reach rod from the inertia weight. The inertia weight and striker are then free to move forward on impact and hit the primer.
Type 2 No.6 Mk 21 Bomb Model 2
Fuzes: D-4(a)
Fuzes: D-4(a)
Overall Length: 42 and 1/4 inches
Length of body: 39 inches
Diameter of body: 9 and 1/2 inches
Thickness of wall: 1/16 inches
Material of wall: Sheet Steel
Type of suspension: Horizontal
Suspension lug: Normal Navy suspension lug is held in place by a steel plate that fits over it and is riveted to the body section.
Suspension lug: Normal Navy suspension lug is held in place by a steel plate that fits over it and is riveted to the body section.
Length of tail: 3 and 1/4 inches
Width of tail: 11 inches
Width of tail fins: 2 and 1/8 inches
Length of tail fins: 8 inches
Width of tail fins: 2 and 1/8 inches
Length of tail fins: 8 inches
Dimensions of tail struts: None
Material of tail: 1/16-inch sheet steel
Type of filling: 36 1-kilogram high-explosive bombs
Weight of filling: 80 pounds
Total weight of bomb: 109 pounds
Charge/weight ratio: 72%
Color and markings: Gray overall with a green-tipped nose and a brown nose band.
Description: The hexagonally-shaped bomb container consists of a blunt-nose assembly and a light tailpiece around which are fitted three sheet steel sections held together by three metal retaining bands. Two steel wires run longitudinally along the exterior of the container and pass through the three retaining band buckles. One wire is attached to the nosepiece; the other is a safety wire which is removed after the container has been placed in the bomb rack.
The nose section is of two-piece construction. The after piece is attached to the sheet steel sides by a welded stud for each section. The forward piece is attached to the after one by three lead sealing strips. The nosepiece, which has a fuze pocket to take the D-4(a) fuze, is filled by a wooden block.
A round metal can containing the burster charge in an annular silk bag is set off-center in the wooden block. The initiating charge in the burster is directly beneath the fuze magazine. The balance of the charge is off-center toward the point where the retaining band release wire is secured to the nosepiece. The purpose of this offset is to exert a more direct pull on the release wire when the charge is detonated.
The tailpiece is held in place by a bungee cord fastened to a hook on the after end of each body section. Two tail fins are riveted to the after portion of the sheet steel section to which the suspension lug is attached. Two metal plates divide the container into three sections in each of which are packed 12 1-kilogram bombs.
Operation: After the bomb container is released from the plane, the aerial burst fuze functions. The burster charge shears the lead sealing strips between the two sections of the nose, blowing the outer piece free from the container and withdrawing the release wire from the retaining band buckles. The retaining bands open and the container sections separate allowing the 36 1-kilogram bombs to fall individually.
The nose section is of two-piece construction. The after piece is attached to the sheet steel sides by a welded stud for each section. The forward piece is attached to the after one by three lead sealing strips. The nosepiece, which has a fuze pocket to take the D-4(a) fuze, is filled by a wooden block.
A round metal can containing the burster charge in an annular silk bag is set off-center in the wooden block. The initiating charge in the burster is directly beneath the fuze magazine. The balance of the charge is off-center toward the point where the retaining band release wire is secured to the nosepiece. The purpose of this offset is to exert a more direct pull on the release wire when the charge is detonated.
The tailpiece is held in place by a bungee cord fastened to a hook on the after end of each body section. Two tail fins are riveted to the after portion of the sheet steel section to which the suspension lug is attached. Two metal plates divide the container into three sections in each of which are packed 12 1-kilogram bombs.
Operation: After the bomb container is released from the plane, the aerial burst fuze functions. The burster charge shears the lead sealing strips between the two sections of the nose, blowing the outer piece free from the container and withdrawing the release wire from the retaining band buckles. The retaining bands open and the container sections separate allowing the 36 1-kilogram bombs to fall individually.
1-kg Antipersonnel bomb
Fuzes: B-5(c)
Overall Length: 11 and 3/8 inches
Length of body: 5 and 1/2 inches
Diameter of body: 2 and 3/8 inches
Thickness of wall: 1/32 inch
Material of wall: Steel
Type of suspension: Carried 36 in a container which is fuzed with a D-4(a) fuze
Suspension lug: None
Length of tail: 5 and 7/8 inches
Width of tail: 2 and 3/8 inches
Width of tail fins: approx. 1 inch at the widest point
Width of tail fins: approx. 1 inch at the widest point
Dimensions of tail struts:
-Diameter: 2 and 3/8 inches
-Length: 1 and 3/8 inches
-Length: 1 and 3/8 inches
Material of tail: Light tinned steel
Type of filling: Type 97 explosive
-TNT: 60%
-HND: 40%
-TNT: 60%
-HND: 40%
Weight of filling: 1 pound 1 ounce
Total weight of bomb: 2 pounds 3 ounces
Charge/weight ratio: 50%
Color and markings: Bomb body may be a steel gray or black. Tail assembly and fuze are aluminum colored.
Construction of body: The body is of one piece light steel construction. It is cylindrical in shape, rounded at the nose and threaded in the base to receive the fuze assembly. The inside of the body is coated with lacquer.
Construction of tail: The tail assembly is made of light tinned steel and is secured to the fuze body by four screws. Four fins spaced 90 degrees apart are soldered to the tail cone and are braced by a ring strut at the after end.
An arming spindle extends from the fuze up through the tail cone, and has vanes attached at the end. A drogue holds the vanes in a safe position.
Operation: When the bomb falls free from the container, the drogue retaining the vanes is carried away by the wind, allowing the vanes to rotate. The motion of the vanes is transmitted through the reduction gear system to the spindle which is threaded out of the striker. To prevent rotation of the striker, a key and keyway system is incorporated in the fuze body and striker. As the spindle rises, it also lifts the gear frame to which is secured a pin retaining the safety detent.
The safety detent, which fits through the fuze body into the striker and holds it in position, is spring-loaded outward, and removal of the safety detent pin permits it to fly out. With the spindle and detent removed, the heavy striker is held up only by a weak creep spring, which it overcomes on impact, initiating the gaine.
An arming spindle extends from the fuze up through the tail cone, and has vanes attached at the end. A drogue holds the vanes in a safe position.
Operation: When the bomb falls free from the container, the drogue retaining the vanes is carried away by the wind, allowing the vanes to rotate. The motion of the vanes is transmitted through the reduction gear system to the spindle which is threaded out of the striker. To prevent rotation of the striker, a key and keyway system is incorporated in the fuze body and striker. As the spindle rises, it also lifts the gear frame to which is secured a pin retaining the safety detent.
The safety detent, which fits through the fuze body into the striker and holds it in position, is spring-loaded outward, and removal of the safety detent pin permits it to fly out. With the spindle and detent removed, the heavy striker is held up only by a weak creep spring, which it overcomes on impact, initiating the gaine.
Type 3 No.6 Mk 23 Bomb Model 1
Fuzes: C-2(a)
Overall Length: 40 and 3/4 inches
Length of body: 21 and 3/4 inches
Diameter of body: 7 and 7/8 inches
Thickness of wall: 1/4 inch
Material of wall: Steel
Type of suspension: Horizontal
Suspension lug: Normal Navy type
Length of tail: 18 and 1/2 inches
Width of tail: 10 and 5/8 inches (excluding tail brake)
Width of tail fins: 4 and 3/4 inches
Width of tail fins: 4 and 3/4 inches
Dimensions of tail struts:
-Length: 7 and 7/8 inches
-Width: 1 and 3/8 inches
-Width: 1 and 3/8 inches
-Thickness: 3/32 inch
Material of tail: Sheet Steel
Type of filling: Picric acid of Type 98 explosive
Weight of filling: 50 pounds
Total weight of bomb: 143 pounds
Charge/weight ratio: 35%
Weight of filling: 50 pounds
Total weight of bomb: 143 pounds
Charge/weight ratio: 35%
Color and markings: Gray overall with a green band around the nose. New type markings may be found.
Construction of body: A cast-steel nose is attached by a continuous weld and 2 rows of 10 rivets each to a tubular-steel body. An anti-penetration ring is welded to the exterior of the nose, 4 inches forward of the rivets. This rind is 2 and 3/4 inches long and has an outer diameter of 7 and 7/8 inches.
A tail cone is held by 1 row of 24 rivets and a continuous weld to a collar which fits into the after end of the bomb body and is held there by 2 rows of screws (14 per row).
A tail cone is held by 1 row of 24 rivets and a continuous weld to a collar which fits into the after end of the bomb body and is held there by 2 rows of screws (14 per row).
Construction of tail: Four fins are spot welded to the tail cone and braced by a single set of box-type struts. A 1/16 inch sheet steel tail brake measuring 10 inches square is welded to the after end of the tail fins.
Type 3 No.6 Mk 27 Bomb (Rocket) Model 1
Please be sure to read the last paragraph in the description
Please be sure to read the last paragraph in the description
Overall Length: 53 inches
Diameter of body: 7.8 inches
Weight of load: 5.5 pounds
Weight of propellant: 22 pounds
Total weight: 145.2 pounds
Maximum speed: 270m/sec
Weight of load: 5.5 pounds
Weight of propellant: 22 pounds
Total weight: 145.2 pounds
Maximum speed: 270m/sec
Color and markings: Gray overall with green and silver nose bands and red tail struts.
General description: This rocket, along with the Type 3 No.1 Mk 28 Model 1, were the only Japanese Navy rockets which were actually under production at the end of the war. It is an aircraft-launched rocket intended for use against formations of large enemy planes, designed to eventually take the place of the Type 99 No.3 Mk 3 for air-to-air bombing.
The bomb consists of three sections: nose, barrel, and tail. The nose section is conical in shape, with a fuze well in the nose and contains a burster charge, and a charge of incendiary shrapnel consisting of white phosphorous filled steel pellets. It is threaded onto the barrel, and secured in place with screws.
The barrel is cylindrical in shape, closed at the forward end, and serves as the container and burning chamber for the rocket propellant. It is fitted with one longitudinal launching rail.
The tail section is conical in shape, and is fitted with four fins of conventional Navy type. It is threaed onto the barrel, and secured in place with screws. The rear end is constricted to form a venturi for the escape of the driving gases.
The propellant is in grains 350 millimeters long and 19.2 millimeters in diameter, and is of the ballistite type, packed into the barrel. It is ignited electrically.
The fuze used in this bomb is 10-second clockwork aerial burst fuze, using the standard Navy fuze clock, housed in a special brass case with a hand operated setting ring graduated in seconds from 0 to 10.
The data on this bomb is the result of incomplete investigation, and must not be considered as specific, accurate information.
The bomb consists of three sections: nose, barrel, and tail. The nose section is conical in shape, with a fuze well in the nose and contains a burster charge, and a charge of incendiary shrapnel consisting of white phosphorous filled steel pellets. It is threaded onto the barrel, and secured in place with screws.
The barrel is cylindrical in shape, closed at the forward end, and serves as the container and burning chamber for the rocket propellant. It is fitted with one longitudinal launching rail.
The tail section is conical in shape, and is fitted with four fins of conventional Navy type. It is threaed onto the barrel, and secured in place with screws. The rear end is constricted to form a venturi for the escape of the driving gases.
The propellant is in grains 350 millimeters long and 19.2 millimeters in diameter, and is of the ballistite type, packed into the barrel. It is ignited electrically.
The fuze used in this bomb is 10-second clockwork aerial burst fuze, using the standard Navy fuze clock, housed in a special brass case with a hand operated setting ring graduated in seconds from 0 to 10.
The data on this bomb is the result of incomplete investigation, and must not be considered as specific, accurate information.
Type 3 No.1 Mk 28 Bomb (Rocket) Model 1
Please be sure to read the last paragraph in the description
Please be sure to read the last paragraph in the description
Fuze: Type 3 Mk 28
Overall Length (w/o fuze): 25 and 1/4 inches
Diameter of body: 4.69 inches
Weight of explosive: 1.32 pounds
Weight of propellant: 4.4 pounds
Total weight: 19.8 pounds
Weight of explosive: 1.32 pounds
Weight of propellant: 4.4 pounds
Total weight: 19.8 pounds
Color and markings: Gray overall with green and brown nose bands and red tail struts.
General description: In its early stages of development, this rocket was designated Mk 19. It is constructed of a light aluminum alloy and carried a high-explosive charge. It is intended for use against large aircraft.
Rocket power is supplied by 16 grains of ballistic type propellant 19.2mm x 350mm. They are contained in the cylindrical barrel of the bomb, and are ignited electrically.
The nose section is ogival in shape, and carried the high-explosive charge. A nose well is provided to take a special small impact fuze similar to the A-3(a). The tail section is constricted to form a venturi, and is fitted with fins, riveted in place, for stabilization. An error of 10 meters at a range of 500 meters is assumed by designers. Two launching rails, 180 degrees opposed, are attached to the barrel of the bomb.
The data on this bomb is the result of incomplete investigation, and must not be considered as specific, accurate information.
Type 4 No.25 Mk 29 Bomb
Type 4 No.25 Mk 29 was in the process of being developed at the end of the war to take the place of the No.25 Mk 3 bombs as a weapon for use against large bomber formations. It was designed either to be dropped in the same manner as the Mk 3 bombs, or to be detonated in the plane by the pilot. The bomb incorporates a larger explosive charge, and smaller quantity of incendiary shrapnel, than do the Mk 3 bombs of the same size.
The nose section of the bomb is conical in shape, and is filled with a wooden block except for a central channel filled with explosive leading into the main charge of the bomb. An adapter is supplied at the nose to receive the Type 3 electric gaine.
The barrel of the bomb is cylindrical in shape, and is filled with incendiary shrapnel of the white phosphorous filled steel pipe type. A central burster charge of high explosive is surrounded by the incendiary shrapnel.
The conical tail section is filled with a central burster charge surrounded by the same type of incendiary shrapnel as is found in the barrel of the bomb. An adapter is provided at the apex of the tail cone to receive the Type 99 Mk 3 tail fuze D-2(a), without centrifugal arming. Tail fins are standard Navy design without rotational offset, such as is found in the Mk 3 bombs.
The bomb is fuzed in the nose with the Type 3 electric gaine fitted with a cable which leads into a firing switch in the cockpit of the airplane. It is to be used when the pilot desires to fire the bomb in the airplane in a suicide attack on bomber formations.
The tail fuze is a Type 90 Mk 3 without centrifugal arming. It is to be used when the bomb is dropped in an air-to-air bombing attack.
This bomb had not gone into production at the end of the war, but was considered by the Japanese to be a practical weapon for defense against heavy bombers.
The data on this bomb is the result of incomplete investigation, and must not be considered as specific, accurate information.
Next Time: Still more IJN bombs!
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