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I.B. 4-lb. Mks I, IE, II, IIE, III, and IIIE. and 4-lb. "X" with 2- and 4-minute delays, Mk I (Obsolescent) |
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Filler and Weight | ||
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| NA, | |||
| Body and Overall Weight | |||
| A hollow, magnesium-alloy body,, 4 lb. | |||
| Color | |||
| Bright Red | |||
| Type of Round, DODIC | |||
| I.B.,Mk X, NA |
| Description: |
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| The Bomb Mk III consists of a hollow, magnesium-alloy body, at one end of which is a cast iron or steel nose ; the body being cast onto the nose during manufacture. A magnesium-alloy tail plug:, which may be of solid or open construction, is screwed into the other end of the body. Fixed to the tail plug by two drive-screws is a tin-plate tail closed by a tail cap. The tail plug houses a striker, creep spring, ferrule having four tabs, and a brass cap holder containing a 1.7-grain detonator. When the bomb IB packed in its case, movement of the striker towards the detonator is prevented by a spring-loaded safety plunger housed in a sleeve fitted into the tail plug. Two vent holes, plugged by cork inserts, are provided in the body to communicate with the space between the cap holder and the filling of the bomb. A strip of primed cambric is located in this space. The Mk IIIE is identical to the Mk III, except for a black powder exploder charge, just abaft the nose plug in the body cavity, which replaces a small quantity of the thermite filler. |
| Use: |
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| Incendiary bombs of many various types, ranging in weight from 4 to 2o0 lb., are at present in service use for operations against different types of targets. The Construction and filling of these bombs differ with the individual types, and no general description can be given here to cover the complete range. |
| Functioning: |
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| When the bomb is released, the safety plunger springs out. On impact, the striker overcomes the resistance of the creep spring, bends the tabs on the striker support (brass cross), and strikes and fires the detonator. The products of combustion from the detonator blow the cork inserts out of the vent holes. The flash from the detonator is conveyed by the primed cambric strip to the priming paste (gunpowder-shellac paste) on the inside of the washer, which ignites the pressed priming composition and in turn the thermite pellets. The magnesium-alloy body starts to melt about 25 sec, after the bomb is ignited, and burns for about 10 minutes. In the Bomb Mk II IK, after ll/2 to 4 minutes, the powder in the burster is ignited and explodes. |
| Munition Components: |
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| Data Source: |
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| OP 1665 Explosive Ordnance British |
| Munitions Tech Data Sheet: |
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