American Projectiles and Explosives - Chemical, Incendiary, Smoke - "AN" Series Bombs (Part 1)

American Projectiles and Explosives



Explosive Bombs

"AN" Series

2-pound Incendiary (Obsolete) AN-M52, AN-52A1, and AN-M52XA1

Overall length: 14.22 inches
Body length: 9.13 inches

Body diameter: 1.68 inches
Wall thickness: 0.35 inches
Tail length: 5.79 inches
Tail width: 1.68 inches

Filling: Thermate

Weight of filling: 0.4 pounds
Total weight: 2 pounds
Charge/weight ratio: 20%

Construction: The hexagonal cast-magnesium alloy body weighs 1.13 pounds.  The bore is one inch shorter than the body length, thus making a solid nose.  There are three vent holes below the primer cap assembly, to assist in initial burning.  The hexagonal sheet-metal tail is secured to the body with three screws.

Filling: Thermate is a composition of 80% Thermite and 20% first fire charge, see below.

Action: The spring-loaded safety plunger is depressed by the adjacent bomb; upon release from the cluster, it jumps out, leaving a thin brass cross holding the striker.  On impact, the striker breaks free from the cross, igniting the primer, first fire charge, and the thermate.  The thermate burns, igniting the magnesium alloy case.  The total burning time is eight minutes.


Remarks: In the Incendiary Bomb AN-M52A1, a primer of heavier metal is used, and the composition of the first fire charge is altered.  The AN-M52XA1 incorporates an explosive charge; otherwise it duplicates the AN-M52A1.






4-pound Incendiary AN-M50 Series

AN-M50A1

Overall length: 21.3 inches
Body length: 13.4 inches

Body diameter: 1.69 inches
Tail length: 8.7 inches
Tail width: 1.69 inches

Filling: Thermate

Weight of filling: 0.63 pounds
Total weight: 3.6 pounds
Charge/weight ratio: 17%


Construction: The hexagonal body of magnesium alloy, weighing 1.25 pounds, has an iron nose plug.  There are three vent holes below the primer cap assembly, to assist in initial burning.  The hexagonal sheet-metal tail is secured to the body with three screws.


Operation: The spring-loaded safety plunger is depressed by the adjacent bomb; upon release from the cluster, it jumps out, leaving a thin brass cross holding the striker, which breaks free on impact and ignites the primer.  The thermate burns, igniting the magnesium alloy case.  The total burning time is 9.5 to 10.5 minutes.

Remarks: AN-M50XA1. (Army: limited standard; Navy: obsolescent) contains 170 grains of black powder in a steel capsule at the nose, replacing a portion of the thermate.  The bomb burns approximately 1.5 minutes, until the black powder explodes, scattering burning magnesium over a wide radius.

AN-M50A2, similar to AN-M50A1, is waterproofed around the primer cap and first fire charge.

AN-M50XA2, similar to AN-M50XA1, has an explosive head consisting of a steel nose cap which houses three tetryl pellets, a detonator, and a delay fuse.  The delay fuse is ignited and sets off the detonator, exploding the tetryl pellets and projecting fragments of steel and burning magnesium.

AN-M50XA3 is identical to AN-M50XA2, except that the assembly around the primer cap and first fire charge is waterproofed.


Type A and Type B

AN-M50XA2 and AN-M50XA3 each have a Type A and a Type B.  Type A indicates that the delay from impact to explosion is two to four minutes; Type B indicates that the delay from impact to explosion is sixty to seventy seconds.

AN-M50TA2 is identical to AN-M50A2, except that it contains a secret toxic agent, which does not affect the burning properties of the incendiary.  Clusters carrying these bombs will have a green and a purple band painted around them.

AN-M50TXA3 combines the toxic feature of the AN-M50TA2 with the H.E. feature of the AN-M50XA3.  It is identical to the AN-M50TA2 as to appearance, except for a new longer, double-mortised steel nose, hollowed out to contain the explosive charge.  Because of the extra length of the nose, the column of therm-64C is 1 and 1/8 inches shorter.

The M50TXA3 is produced according to only one design or type, which gives a delay on the explosion of the H.E. charge of from 1 and 1/2 to 6 minutes.  A heat-sensitive detonator 2.556 inches long, which ignites at 300 degrees Celsius is housed in a hole drilled centrally through the upper part of the steel nose.  A 1/16-inch steel disk is placed in the bottom of the filling cavity of the bomb body, thus covering the top of the hole in the nose and insulating the detonator from the heat of the burning bomb.  The H.E. charge consists of tetryl pellets.






4-pound Incendiary AN-M54 Series (Obsolete)

AN-M54
Overall length: 21.35 inches
Body length: 13.6 inches

Body diameter: 1.69 inches
Tail length: 10 inches
Tail width: 1.69 inches

Filling: Thermate

Weight of filling: 1.6 pounds
Total weight: 4 pounds

Charge/weight ratio: 40%

Construction: The bomb body is a steel cylinder having a hexagonal nose plug.  The fuze is installed in the tail plug assembly.  There are three vent holes below the primer cap assembly, to assist in initial burning.  There is a hexagonal hollow sheet-steel tail.

Operation: The spring-loaded safety plunger is depressed by the adjacent bomb; upon release from the cluster, it jumps out, leaving the firing pin riding on a creep spring.  On impact, the firing pin overcomes its creep spring and strikes the primer, igniting the thermate, which melts the steel body and releases molten iron.


Remarks: AN-M54X is the same as AN-M54, except that next to the hexagonal nose plug a small portion of the thermate charge is replaced by a steel capsule containing 170 grains of black powder, which explodes and scatter the molten iron after the bomb has burned for about one minute.  It is limited standard for the Army, obsolete for the Navy.

AN-M54XA1 is the same as the AN-M54, except that inside the hexagonal nose plug there is a steel cylinder containing a tetryl high-explosive charge with a delay fuse and a detonator.  A thin spacer of magnesium is between the thermate and the fuse opening of the explosive cylinder.  After one minute of burning, the fuse is ignited, exploding the tetryl.  These bombs are no longer being procured for naval service, and should not be used except when Incendiary Bombs AN-M50A2 or AN-M69 are not available.  It is limited standard for the Army, obsolete for the Navy.

6-pound Incendiary AN-M69 and AN-M69X

Overall length: 19.5 inches
Body length: 19.5 inches

Body diameter: 2.87 inches
Wall thickness: 0.042 inches
Tail length (streamer): 54 inches

Filling: Gelled gasoline (NP or IM)

Weight of filling: 2.8 pounds
Total weight: 6 pounds

Charge/weight ratio: 46%

Construction: The bomb body is a hexagonal case with a nose cup welded to the forward end.  The nose cup, fuze and powder charges are sealed off from the rest of the case by an impact diaphragm and plug held in a cup-shaped sealing diaphragm.  The incendiary oil filling is held in a cheesecloth sock situated between the forward sealing diaphragm and the tail cup.

The tail assembly consists of a tail cup, tail retainer, and disc.  The tail cup is secured to the hexagonal case by beading, crimping, and heating.  Four gauze streamers, each 54 inches long, are attached to the tail retainer by the tail disc to stabilize the bomb and reduce the terminal velocity.

Operation: The spring-loaded safety plunger jumps out of the Fuze M1 upon release from the cluster, arming the fuze.  On impact, the striker overcomes its spring and detonates the primer cap, which ignites a lead-coated spitter fuse.  The spitter fuse burns from three to five seconds, allowing penetration, and ignites the black-powder booster charge.  This ignites the igniter-ejector charge consisting of two bags of black powder and oiled magnesium powder.  The combustion blows off the tail cup, ignites the incendiary filling and ejects it for a maximum of 75 yards.


Remarks: The bomb and the delay are calculated to permit penetration inside a structure before detonation.  The incendiary oil filling is of a very sticky composition and will normally adhere to any object, including vertical walls.

The AN-M69X incorporates a 4.5-ounce charge of tetryl to produce an anti-personnel effect.  Overall dimensions of the AN-M69X duplicate those of the AN-M69, but the amount of incendiary mixture is reduced (0.4 pounds less).  Operation of the Fuze M1 ignites a safety fuze lead terminating in the Detonator M106, which explodes the tetryl, fragmenting 65% of the bomb case after ejection of the incendiary material, following a pre-determined time delay of 0.5 to 6 minutes (30% - 1/2 minute; 30% - 2 minutes; 40% - 6 minutes).  The time delay is varied by adjusting the length of the safety fuse.

Next Time: Chemical, Incendiary, Smoke - "AN" Series Bombs (Part 2)