American Projectiles and Explosives - Chemical, Incendiary, Smoke - "MK" Series Bombs

American Projectiles and Explosives



Explosive Bombs

"MK" Series

100-pound Incendiary Mk I and Mk 28 (Obsolete)

Overall length: 45.5 inches
Body length: 33.7 inches

Body diameter: 8 inches
Wall thickness: 0.05 inches
Tail length: 11.75 inches
Tail width: 11.3 inches

Filling: Gasoline, Gasoline-Gel, Gasoline and Waste, rubber

Weight of filling: 42 to 45 pounds
Total weight: 65 to 68 pounds
Charge/weight ratio: 65% (approx.)

Construction: The bomb is of three-piece sheet-steel construction, with a hemispherical nose piece and aconical tail cone welded to a tubular body.  The bomb has two suspension lugs on bands or a single lug on a band near the center of gravity.  The tail assembly consists of four sheet-steel vane welded to the tail cone, which, in turn, is welded to the body.

Color: The bomb is painted grey overall, with a bright red disc, four inches in diameter, in the middle of the body.


Remarks: This bomb is similar to the 100-pound Incendiary Bomb AN-M47A2, except that it is equipped with a filler cap.  Both bombs are prone to leak and should be examined frequently.

There is also a 100-pound Incendiary Bomb Mk I, which is almost identical to the old Army M47, both of which are obsolete.






100-pound Chemical Mk 42

For photo, see above

Overall length: 39.43 inches
Body length: 27.7 inches

Body diameter: 8 inches
Wall thickness: 0.17 inches
Tail length: 9.46 inches
Tail width: 11 inches

Filling: Mustard gas

Weight of filling: 43 pounds
Total weight: 86.5 pounds
Charge/weight ratio: 50%


Construction: The steel tube is swaged aft.  An adapter screws into the nose and is threaded to receive the fuze.  A burster tube containing TNT, running the length of the bomb, screws into the after end of the adapter.  The after end of the body is closed by a male base plate, which is threaded for the tail assembly to be fitted.  The bomb is filled through the nose.  Suspension is by two lugs seven inches on either side of the center of gravity or a single lug 180 degrees removed and at the center of gravity.  The bomb has a box-type, four-fin tail, secured by a locking nut.


Markings: The bomb is painted olive drab overall, with two green bands 1/2 inch wide and 1/2 inch apart abaft the nose.

50-, 100-pound Floating Smoke (Obsolescent) Mk 3 Mod 0 (100-lb), Mk 1 Mod 1 (50-lb), Mk 1 Mod 2 (50-lb)

For photo, see top

Mk 3 Mod 0

Overall length: 48.5 inches

Body diameter: 10.25 inches
Tail length: 13 inches
Tail width: 14.25 inches
Filling: HC Mixture
Weight of filling: 59 pounds
Total weight: 102 pounds

Charge/weight ratio: 57.8%


Mk 1 Mod 2

Overall length: 38.29 inches

Body diameter: 8.85 inches
Tail length: 9.4 inches
Tail width: 8.94 inches
Filling: HC Mixture
Weight of filling: 28 pounds
Total weight: 54 pounds

Charge/weight ratio: 51.8%

Construction: An aluminum nose casting, carrying a pyrotechnic charge, is attached to a hollow wood float which provides buoyancy.  The nose carries a water-impact fuze, and at the tail of the float is a valve cap with the valve to prevent water from leaking into the interior of the bomb.  The rear of the bomb is conical in shape, and the aluminum nose is hemispherical.  The tail consists of four fins bolted to the rear of the bomb, with four tubular struts bolted to the fins.  The fins do no extend upon the rear end of the bomb.

Suspension: Two movable suspension bands are used on the Floating Smoke Bomb Mk 3 Mod 0; the Mk 1 Mods 1 and 2 may have either one or two suspension bands.  The latest issue has one band and one attached lug, so that the bombs may be suspended from the single- and double-hook racks.


Action: Impact operates the firing mechanism in the nose, detonating the primer, which in turn ignites a length of time fuze giving a delay of 18 seconds, during which time the smoke bomb is returning to and becoming stable on the surface of the water.  The time fuse ignites the quick match which, in turn, ignites the starting mixture and this initiates the action of the smoke mixture.  Gas pressure formed by the burning smoke mixture breaks the vent discs and opens the valve cap at the tail end of the wooden float.  The bomb then evolves a dense white smoke for about 7.5 minutes in the Mk 3 Mod 0; 2.5 to 5 minutes in the Mk 1 Mod 1 and 5 to 7.5 minutes in the Mk 1 Mod 2.


Remarks: This bomb should be dropped from an altitude of over 500 feet and should not be dropped in less than 40 feet of water where the bottom is soft enough to cause the bomb to stick and fail to return to the surface.  While designed for use over water, the bomb may also be effective if dropped over ordinary loam soil, if dropped from an altitude under 2,000 feet.  If dropped from over 2,000 feet or if dropped from any altitude onto very hard rocky ground, the bomb will usually deflagrate.  The HC mixture is a pressed powder, safe under any normal storage or handling conditions.  The smoke, while harmless in the concentration found in smoke screens in the open, is toxic in more concentrated form.

The 50-pound Floating Smoke Bomb Mk 1 Mod 2 differs from the Mod 1 in that it has a longer burning time, with a maximum of 7.5 minutes, as in the 100-pound Mk 3 Mod 0, and a minimum of 5 minutes.

Next Time: Chemical, Incendiary, Smoke - "AN" Series Bombs

American Projectiles and Explosives - Chemical, Incendiary, Smoke - "M" Series Bombs

American Projectiles and Explosives



Explosive Bombs

"M" Series

10-pound Incendiary M74

Overall length: 19.4 inches
Body length: 19.4 inches

Body diameter: 3 inches
Tail length: 6.3 inches
Tail width: 2.5 inches
Filling: PT 1 or NP

Construction: This bomb has the same type of construction as the 6-pound Oil Incendiary Bomb AN-M69, with a sheet-steel leak-proof casing and a nose cup housing the fuze.  A small chemical container, located immediately behind the dome of the nose cup, is filled with white phosphorus, to aid ignition of the incendiary composition and produce smoke.  In bombs with NP, the filling is enclosed in a cheesecloth sock; if PT 1 is used, it is loaded directly into the bomb.  The Incendiary Bomb M74 has a telescope-type tail which fits inside the tail cup and is ejected under spring pressure when the bomb is released from the cluster.  A well inside the tail cup holds the tail sleeve when the assembly is compressed in the cup.

Operation: The striker of the Fuze M142 or M142A1 ignites the primer, which sets off the booster and main ejection charge.  This activates the auxiliary ejection-ignition charge.  Expanding vases rupture the dome-shaped ejection diaphragm, which forces the WP-filled cup, incendiary filling, tail cup, and tail assembly out of the bomb casing.


Remarks: Do not reinsert arming pin after it has been ejected, as it may cause the fuze to function.

The experimental bombs of this type with other fillings are designated the E5 series.  The experimental bomb with a white phosphorus filling has been rejected; however, the one with the mustard filling, E5R8, is still under development.  This bomb will be carried int he Cluster E61 holding 38 bombs (Cluster Adapter M23).




Cluster Adapter E6R2

Overall length: 59.06 inches
Body diameter: 14.69 inches
Tail width: 16 to 18 inches


General: The cluster adapter has a thin steel body that is shaped like a bomb, except the nose is not rounded off to make a full hemisphere.  A standard-type bomb fin is affixed to the rear of the adapter, and a fuze fits in the nose.  Hoisting and suspension lugs are located at the top.  Internally, the adapter is equipped with cluster bars for positioning of the bombs when loaded.  An L-shaped angle bar runs the entire length of the adapter along the bottom cluster bar.  Into the angle bar is fitted a light steel tube which encloses a length of primacord that extends from the nose fuze to the other end of the cluster adapter.  When the cluster is filled, the bomb are packed nose-forward, 19 in the front half of the adapter and 19 in the after portion.  The assembly is held together by nine nailless steel straps.  The cluster adapter then becomes a 500-pound aimable cluster that will fit any 500-pound bomb station, and, when dropped from high altitude, approximates the trajectory of a 100-pound demolition bomb.

Operation: On release, the arming wire is pulled, allowing the clockwork to start and the vanes to turn.  When the vanes have made the proper number of turns, a striker-pin safety block falls out, completely arming the fuze, so that it functions upon expiration of the predetermined time setting.  Firing of the fuze detonates the primacord, which runs the full length of the adapter.  Explosion of the primacord breaks the nine nailless steel straps, allowing the cluster adapter wall to open and the bombs to scatter.


Remarks: If desired, the cluster adapter may be kept intact during the entire period of flight, bursting open on impact.

This adapter is being replaced by the Cluster Adapter M28

Cluster Adapter M10A1

No picture available

Overall length: 56 inches

Diameter: 15.3 inches

General: The cluster adapter is streamlined in shape, and, when filled, it becomes a 500-pound aimable cluster designed to be carried by any plane equipped to carry a 500-pound bomb.  Clusters formed with this adapter are the AN-M14, which contains 104 Incendiary Bombs AN-M50TA2, four AN-M50XA3 Type A, and Two AN-M50XA3 Type B; and the AN-M17A1, which contains 88 Incendiary Bombs AN-M50A2, 16 AN-M50XA3 Type A, and six AN-M50XA3 Type B.

The cluster adapter consists of a thin metal case with a channel bar extending through the center, and a standard tail fin fixed to the after end plate by means of a single heavy bolt.  At the forward end, a rounded nose fairing is fastened to the forward end plate.  From the fuze seat, a length of primacord extends through a thin metal tube to the after end of the adapter.  The adapter is equipped with three suspension lugs, the center lug added for use in British planes.  When the cluster adapter is loaded, the bombs are packed around the channel bar and the assembly is held in place by nine metal straps.

Operation: On release, the arming wire is pulled, allowing the fuze to arm and fire at the pre-set time.  When the fuze fires, the primacord is detonated, breaking the metal straps holding the assembly together and allowing the bombs to fall free.


Remarks: The Cluster Adapter M10A1 is similar in appearance to the E6R2, but differs internally.  The bombs in the M10A1 are packed around a channel bar, while in the E6R2 the cluster bars surrounding the bombs hold them in place.

Cluster Adapter M23

Overall length: 59.5 inches

Body diameter: 14.75 inches
Tail width: 19 inches

General: Cluster Adapters M23 are used in forming 500-pound aimable clusters of incendiary or chemical bombs.  Cluster may be carried by planes equipped to handle 500-pound bombs.  They are designed for use in high- and medium-altitude bombing, the flight characteristics resembling those of the Practice Bomb M38A2

Description: The cylindrical halves of the cluster wall are joined at the top by a suspension bar and at the bottom by a burster-shield support bar.  Cluster bars, fitted into the end plates, hold the bombs in position inside the adapter.  Ballast weights are bolted by studs to the front and rear of the adapter's end plates.  Nine steel straps, drawn tight and fastened by a metal connector, are attached to release buckles which are placed on alternate sides of the suspension bar.  The buckles are held closed by two release wires attached to a release lever, which in turn is attached to a stud on the tail cone.  The tail assembly is composed of a modified box-type fin on a conical support, with two tail-fuze adapters attached to opposite sides of the cone.  The long stud, which extends through the rear ballast weight, supports the tail assembly.

The primacord wiring of the adapter is in two sections.  A metal tube channels a 60-inch length of primacord from the forward end of the burster shield, through the tail cone, and into the base of the "long" fuze adapter.  A 31-inch length extends from the tail cup into the "short" fuze adapter.


Clusters: Bombs are clustered in two sections, 19 bombs in each, with the nose to the front of the cluster.

Operation: On release, the arming wires are withdrawn and the two fuzes arm.  Upon expiration of the time setting, the "short" fuze operates to set off the booster and the primacord, which is channeled to the fin-retaining cup.  The cone is blown off by the primacord detonation, thereby withdrawing the buckle release wires and opening the cluster.  Upon failure of the "short" fuze to function, the "long" fuze operates two seconds later.  This detonates the primacord extending the length of the cluster, which shears the steel straps and releases the bombs.


Remarks: Some lots of adapters were shipped without buckles and release wires, the release of the bombs being dependent on the severing of the steel strapping bands.  The primacord from the "short" fuze is taped at a right angle to the primacord leading from the "long" fuze, to form one primacord assembly.  Operation of either fuze would detonate the primacord extending the length of the cluster, thereby severing the steel strapping bands and releasing the bombs.





115-pound Chemical M70

Overall length: 48.7 inches
Body length: 40.4 inches
Body diameter: 8.1 inches
Wall thickness: 0.224 inches

Tail length: 12.9 inches
Tail width: 10.9 inches
Tail weight: 3.5 pounds

Filling: Mustard (H)
Weight of filling: 57.1 pounds
Total weight: 122.5 pounds
Charge/weight: 46.6%


Construction: The bomb is made from a seamless steel tubing, with an ogival nose threaded to receive the nose fuze.  A burster-well tube runs the entire length of the body, fitting into a positioning cup at the rear.  The tail assembly consists of four fins welded to a sleeve, which is secured by a locking nut threading into the tail closing block.  The fins are supported by box-type struts.


Suspension: The bomb is carried horizontal by dual lugs seven inches on either side of the center of gravity, or a single lug 180 degrees removed at the center of gravity.

A cluster of four M70's is formed by using the Cluster Adapter M22.


Remarks: On impact, the fuze functions instantaneously, setting off the burster charge, which explodes the bomb and scatters the main filling.

The M70 can also be filled with white phosphorus, or with IM or NP incendiary mixture.





10-pound Smoke M77

Overall length: 19.5 inches
Body length: 19.5 inches
Body diameter: 2.9 inches

Filling: HC
Weight of filling: 9.5 pounds
Total weight: 13 pounds
Charge/weight: 73%


Construction: The body is a sheet-steel case extending the entire length of the bomb.  The tail cup fits into the after end of the casing, having a dome housing the Fuze M4.  The bomb does not have a device for stabilization in flight; therefore, an all-ways fuze is employed.

Operation: As the bombs are released from the cluster from the cluster, the arming pin is forced out by its spring, permitting the safety pin to enter the cavity in the striker.  Impact forces the striker and sleeve together, piercing the primer, which in turn ignites the first fire mixture and subsequently the H.C. smoke mixture.  The heat generated by the burning of the first mixture and the H.C. smoke mixture melts the zinc-alloy fuze body.  The smoke is then emitted through the fuze hole in the tail cup.


Remarks: Once the arming pin jumps out, the fuze is armed, and any attempt to reinsert the pin may cause the fuze to function.

Next Time: Chemical, Incendiary, Smoke - "MK" Series Bombs