4 lb. Incend. Bomb Mks III & IIIE30 lb. Incend. Bomb Mk IV








Simple impact striker

4 LB. I.B.


End face of nose, and


body aft of nose for 2"


painted bright red; Mk IVE


has ½" aft of bright red

Mks IV & IVE


nose coloring.




(Also Mk V, VE, and 4 lb. "X" with


1.67" (hexagonal in shape)

2 & 4 minute delays, Mk II - See


4 lbs. approx.

"Similar Incendiaries" below)












The bomb is hexagonal is snape, having a hollow magnesium-alloy body, cast iron nose, with body cast to the nose in manufacture. A tinplate tail, closed by a tail cover, is secured to the other end of the body by three drive-screws, which also hold a steel striker housing in position in the body. At the tail end, the body is counterboard to ac-commodate an igniting mechanism consisting of a striker, located in the striker housing, and a steel plate seated at the bottom of the ecounterbore and containing a 1.7 grain detonator. One end of the striker is pointed, and the other end projects through a hole in the striker housing. The edge of this hole is chamfered to permit a thin brass cross secured to the striker, to be bent and pullet through the hole when the bomb functi-ons. This cross forms a striker support during transit and storage. Movement of the striker towards the detonator is, when the bomb is packed in its case, prevented by a spring-loaded safety plunger housed in a sleeve. Two vent holes, plugged by cork in-serts, are provided in the tail end of the body and communicate with the space bet-ween the igniter mechanism and the bomb main filling. A strip of primed cambric is loca-ted in this space. The filling consists of a cardboard washer filled with gun-powder-shellac priming paste, a quantity of pressed priming composition, and the thermite igni-ter pellets.


These incendiaries are carried in the Small Bomb Container or in Cluster Projectiles.


When released from the container the safety plunger springs out, and on impact with the target the striker moves down, breaking free from the brass cross striker sup-port, and firing the detonator. The flash from the detonator ignites the primed cambric strip and the gunpowder-shellac paste, and the products of combustion blow the cork inserts out of the vent holes. The paste ignites the pressed priming composition which, in turn, ignites the igniter pellets. The magnesium-alloy body starts to melt about 25 sec. after the bomb has ignited, and burns for about 10 minutes. In the Mk IVE, after 1½ to 4 minutes, the gunpowder in the burster is ignited and explodes.


4 lb. Mk V and VE: Similar to the Mk IV and IVE, except for the following differences: (a) bomb is initiated by a cap and anvil being struck by the striker, the striker having a blunt point; (b) the cap is supported by an aluminum plate; (c) the striker housing is made of aluminum; (d) a different kind of pressed priming composition is used, being more violent than the priming compositions used in the Mk IV bombs, and causing some of the magnesium-alloy to scatter when the bombs are ignited. This bomb is actually the U.S. AN-M 50.

4 lb. X, with 2 & 4 minutes delays, Mk II: Similar in construction to the Mk IV, ex-cept that a C.E. exploder is contained in the steel nose, as shown in the drawing oppo-site, this exploder being initiated after delay of either 2 or 4 minutes, depending on which bomb it is. The nose for 3½" is painted dull red, with two ¼" black bands separa-ted by a 1" bright red band painted around this dull red nose. A second bright red band, ½" wide and ½" aft of the dull red coloring, indicates that the incendiary is of the ex-plosive type.


No "E" marks now produced. The small black powder charge was not lethal, but for scare purpose only.

4 lb. Incend. Bomb Mks III & IIIE30 lb. Incend. Bomb Mk IV