British Bomb, 250 lb Multiflash, No. 7 Mk 1, No. 7 Mk 2, No. 21 Mk 1, No. 21 Mk 2, No. 21 Mk 3, No. 21 Mk 1C
No. 7 Mks 1 and II and No. 21 Mks I and II Bodies - The actual construction of these bombs is the same as that of the No. 1 Tl Bomb Mk I except for a different arrangement of the filling. which requires a different type of central flash tube and priming, and eliminates the use of the division disc.
The flash units are packed around the central tube in seven layers, each of which contains 26 units; and an eighth layer, containing 28 units, is positioned above the central tube. The flash units are positioned so that the primed ends of each two layers contact one of the four primed cambric washers for purposes of ignition. Each of these- washers engages a strip of primed cambric, which 7s secured around a set of holes in the central tube.
The Bomb No. 7 Mk II differs from the No. 7 Mk I as the No. 1 Mk II differs from the No. 1 Mk I.
No. 21 Mk III and IC Body - The body, tailplate, burster container, and ejector plate of this bomb are the same as in the Tl Bomb No. I Mk I. The interior arrangement of the Bomb No. 21 Mk III differs from the No. 7 and No. 21 Mks I and II in that the central flash tube extends completely through the bomb to the tail fuze pocket, thus displacing two of the flash units. The Bomb No. 21 Mk IC differs from the No. 21 Mk III as the No. 1 Mk IC differs from the No. 1 Mk III.
Tail Construction: Same as for the No. 1 TI bomb tails.
The bomb is suspended by a single lug, which is welded to the body.
This bomb is used to distinguish a genuine ground marker from one simulated by the enemy.