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3inch tail on a 4.2inch

BMG50

Well-Known Member
Premium Member
A friend of mine has a 4.2 base eject mortar round relic inert. but the tail has a 3inch tail on it, is this normal or is this a heath robinson put together. but saying that this was found in its condition.
 

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That is a Tail Unit No 8 produced for the Bomb 4.2" Base Ejection Discarding Sabot (BEDS) BE Smoke bomb.
The Tail Unit No 8 produced for the 3" Mortar is entirely different.
Most of the 3" and 4.2" bombs were fitted for Fuzes 152 or 162 with 1.375" fuzehole, but the BE Smoke bomb required a 2" fuzehole to take the Fuze No 390.
A bomb was made to match the performance of the 4.2" HE bomb, but retaining the base ejection capability to provide screening smoke rather than bursting smoke.
The BEDS Smoke Bomb used the Fuze 390, which was used in the 3" mortar, but the timing ring composition was changed to suit the longer burning time required to match the increased range of the 4.2" bomb, over the 3" bomb.
On firing, the pins retaining the sabot sheared and the sabot fell away on leaving the 4.2" mortar barrel.
You can see the sabot on the relic bomb.
 
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Thanks for the reply, so is the relic bomb fitted with a 3" tail on a bomb body that is much larger in diameter than the tail, surely it mush be unstable in flight.
 
Thanks for the reply, so is the relic bomb fitted with a 3" tail on a bomb body that is much larger in diameter than the tail, surely it mush be unstable in flight.

Hmm, just looking at the image one can see that the tail fin unit (well the bore-riding tabs) is (are) approximately the same diameter as the bore-riding 'sabot' around the modified 3-inch bomb's middle area. As such good luck loading it into a 3-inch mortar.

Ignore me, I was only looking at the first image, I didn't even see the second corroded one. And yes, this does seem to have the wrong fin unit and it seems to be missing its sabot.
 
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I should have said 'Increased range of the 3" Mortar bomb with the flange to fit in the 4.2" mortar'.
 
The relic bomb has not retained its sabot ring, the body has the raised sections with the groove between to take the sabot ring. The tail unit no8 for the 4.2" is, as stated totally different than the 3" tail unit but that relic example is not a 4.2" tail. The fins are much longer and almost reach the base of the bomb, just like a 3".
IMG_1389.jpg
 
I am editing posts and further replies are being added while I am doing so.
I should point out that this is a discarding sabot bomb and on firing the the sabot retaining pins shear, but the two ring sections are retained in position by the bore, but on clearing the barrel they drop away leaving a ballistically clean, virtual 3" bomb which can be mixed and matched with HE bombs to provide screening smoke for a prepositioned attacking force. While one mortar is set to hammer the enemy position, another firing slightly shorter range is laying down an attack smoke screen.
 
I think that the relic bomb has a bent over front vane at the top and who knows what distortions may occur on landing and burial.
Unless you have the full life history of modifications and experimentals it is hard to say what is what.
 
Many thanks for your input much appreciated. It appears that when the bomb was found it was in pieces and the 3" tail was in the vicinity and was assumed it was part of the 4.2, when in fact the tail was part of a 3" be smoke.
 
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