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2" WW2 Mortar

Rondee

Member
Hello,
This is my first time here and I'd like some help uncover a tragic event that happened in 1945.

Boys found a 'blind' 2" mortar on a mountain training area, took it home and tampered with it the following day killing 3 boys aged between 14 and 6. I read the coroner's inquiry in the local press archive and a lucky witness testified: Heasked me to hold the bomb while he screwed off the fin. Ted then knocked offthe cap and pulled out a screw with a pliers and a spring came out. Then he puta screwdriver in a hole in the bomb and white powder came out. The boy's mother called him in for tea and that's when the bomb exploded as he sat down at the table. Could anyone guess which of the 2 springs this is likely to be: the detent or the detonator and if the 'white powder' was the pentolite or the TNT.
I'd appreciate any information surrounding this and thank you in advance.
Kind regards,
Rondee.
 
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This diagram from the manuals will help you understand how the 2 inch fuze works. This type is the 161 which has a safety pin which holds the detent in place if accidentally dropped before firing. The 151 early type fuze didn't have this feature of a safety pin. When the detent is released upon firing by the recoil moving it back, it releases the ball bearing which holds the stiker in place. The striker free then moves to the top of the inside windshield or brass dome by its spring and allows the shutter (spring loaded) that holds the det cap ( very sensitive ) to move in line with the striker. Upon landing the striker hits the det cap and flashes down into a small stem of sensitive C.E composition explosive about 3mm in diameter x 5mm long which is held in a round disc 5mm thick x 30mm wide. this bursts into the main CE pellet as you say penolite which is a more powerful explosive (used in hollow charge bazooka rounds and other devices this then busts into the TNT or amatol main charge. I think TNT has a booster charge in some 2 inch mortar rounds. The detent and ball is only there to release the striker. If the detent is activated by accidentally dropping the mortar round or fired but doesn't go off because it glanced off an object, if its dropped again then the striker could hit the det cap under inertia even though the windshield cap is not dented or crushed.
 

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Thank you very much and your reply which was thorough and illuminating. I'd like to ask a couple of further questions on the 2" mortar.

In the coroner's inquiry a witness testified that that the boy poked a screwdriver into a hole of the mortar he's found on a training range in 1945 and "white powder came out". 1: Would this hole be where the safety pin was and 2: would a screwdriver enter the 'det cap' and the CE charge via this hole?

The background story is of boys finding 2 'blinds' in a training area in 1945, took them home to make "ornaments of them" but curiosity and stupidity led one of them to tamper with one resulting in the his and 2 other boys' deaths. The subsequent coroner's inquiry was sketchy about the accident, the responsibility of the Army in safeguarding the public and this is what I'm trying to piece together. One of the innocent victims was a cousin who happened to be playing marbles nearby and was 10 when he was killed.

Kind regards.
Rondee.
 
From memory the fuse is armed when fired by inertia releasing the firing pin shutter.
If the firing pin did not hit the primer upon hitting the ground then it would not go off but if it was dropped again on hard surface it my cause it to fire.......
 
The round could be white phosphorus which is exactly the same as a HE round using same fuze but the place where the explosive is in a HE round has a small sealed tin that contains the WP.
As for poking around with a screw driver, it all depends on the condition of the mortar round in question and its condition ie was there a hole in the body, was the fuze windshield missing or damaged or a hole in the side of the fuze upon impact or another HE round which exploded next to the blind caused the hole.
As for the body of the mortar round its very thick to poke a hole in with a screwdriver unless they drilled a hole in it and poked around after wards. A hole in the side of the fuze any part is very thick to poke a hole through. The top windshield is more likely a place to get into the fuze but not possible to release white powder as the compound of the CE and main charge is deep within the bomb, unless you drill.
I suspect that the striker was in alignment with the det cap holder and the screwdriver pushed the striker against the cap, doesn't need much to set of a det cap as its different to a pistol or rifle primer cap with a different composition. The mortar det compound is very sensitive that sets of on the lightest strike.
 
Thank you very much and your reply which was thorough and illuminating. I'd like to ask a couple of further questions on the 2" mortar.

In the coroner's inquiry a witness testified that that the boy poked a screwdriver into a hole of the mortar he's found on a training range in 1945 and "white powder came out". 1: Would this hole be where the safety pin was and 2: would a screwdriver enter the 'det cap' and the CE charge via this hole?

The background story is of boys finding 2 'blinds' in a training area in 1945, took them home to make "ornaments of them" but curiosity and stupidity led one of them to tamper with one resulting in the his and 2 other boys' deaths. The subsequent coroner's inquiry was sketchy about the accident, the responsibility of the Army in safeguarding the public and this is what I'm trying to piece together. One of the innocent victims was a cousin who happened to be playing marbles nearby and was 10 when he was killed.

Kind regards.
Rondee.

The attached may be of interest (see serial 4181).

AccReg-002.jpgAccReg-003.jpg
 
Very interesting reading, thanks Norman for showing. Did they have this type of accident book throughout the war. I did see documentation about casualty rates during training at Kew public records office.
 
Thanks for this fascinating book. I wonder if anyone can help unravel the procedure for dealing with 'blind' on a training area in N Wales in March 1945. Here's the background story.

Boys found 2 blinds on the training area, they took them and 'empty' mortars (smoke mortar casings?) home on the bus and the following day while tampering with the HE 2" mortar it explodes killing three boys. A Major Jones gave evidence in the coroner's inquiry that about 2% of the 1300 fired every month were "blinds and every effort was made to recover them or a red flag was placed in the vicinity". The area was rough ground with thick bracken/gorse and a river. They had to wait for the bracken to die back or for the river to recede before recovering blinds. What I'd like to know is: 1 - did they (the army in training) really bother to find them, 2: did they call a specialist bomb disposal crew instead, 3: how did they deal with the UXO and 4: 2% of 1300 is 26 and that's a lot of UXO to be laying around per month which implies it was impossible to recover all.
The major said that all blinds were recorded in a book, their positions mapped and a record was sent to the police every month. Finally, he testified that there were warning signs in the area and although the boys entered the area knowing the risk, a witness testified there was no barbed wire fence and no red flags.
Many thanks,
Rondee.
 
Although they had safety measures back then, you have to remember that it was different times compared today health and safety wise. The rounds were on military land with a warning sign back then that was good enough to warn troops dog walkers. Even today they just have two strand barbed wire fence on restricted areas. What ever you put up kid being kids especially boys love war stuff and will trespass for souvenirs. I know as I and many of my friends back in the early 70s used to play and find things on MOD land and generations before and after. If you look at bomb sites in London during the war, kids were always on the look out for the the best bomb shrapnel.
The army did look out for blinds and dealt with them, it’s in in the manuals. They usual delt with a blinds where they landed grenade and mortars. If there was a problem ie near a building I think it was sand bagged to keep down the blast. They did this on butterfly bombs in awkward places.
The army was responsible towards their men and civilians. Remember the forces were trying train a conscript army from the useless to the intelligent and many accidents happened. I noticed the 77 grenade mentioned a bit, quite an awkward grenade to use I suspect with its tape flying all over the place and it’s reliability to go off.
If you go to the archives there were a lot of problems with 2” mortar star shell, smoke and para illum rounds usual damp water proofing issues because of black powder being its ignition source. HE and WP did have issues if landed on soft ground or a glancing shot from a tree etc plus the manufacturer factor of war time munitions being made compared to peace time munitions.
Red flags only fly when a area is active, back then a warning sign was good enough. I think the boys knew that they shouldn’t be there looking for bombs. I am sure parents and relations warned them as well as schools.
 
BMG50 the land service ammunition organisation kept records of all accidents on an annual basis (see register dates). Eventually these were formalised and circulated to all command HQs, not just ammunition departments.
By the 1950s, to my knowledge, they were circulated every 6 months and now include ammunition defects.
 
Two variants of the Abram Games "blinds" posters (courtesy IWM online poster collection), each including a 2" HE mortar round. The message - if not the actual posters - was supposedly widely circulated, but unfortunately not always observed, especially by children.
 

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Those two pages make interesting reading. I'm surprised the victim of 4171; 69 Grenade, Kicked Blind, lived to tell the tale. The 77 Grenade claimed more than its fair share of victims and surprisingly, they appear to have survived their phosphorous burns. Presumably 4186 is a fatal accident as opposed to suicide, if it were the latter I would have expected an officer to use his issue revolver.

TimG
 
Thanks so much again; all this is building a clearer picture in my mind. I now have a theory how the boy exploded the mortar.

After taking the 'blind' it home a witness saw him tamper with it in the street; he'd taken off the windshield cap then removed the striking pin ("he pulled out a screw with a pliers and a spring came out..."). He then inserted a screwdriver into the hole left by the striker pin. In effect, the screwdriver's sharp point became a replacement striking pin. This is the "hole" the witness referred to. As you know, the hole is directly above the various charges and he might have punctured the sealed tin that contained the phosphorous ("Then he put a screwdriver in a hole in the bomb an white powder came out".) At some stage poking about in the hole detonated the round. What I don't quite get is why did he not touch the septum first - the charge immediately below the sharp point of the striker? This would be sitting on top of the CE charges?
Regards,
Rondee
 
Thanks so much. I've been looking for warning posters the schoolboys might have seen without luck until now! Wonderful - a very big thanks.
Rondee.
 
If he took out the striker then he would have hit the det cap unless it stuck in place to the side which caused the blind in the first place. Directly underneath the det cap, in the correct position the point the firing pin would strike, is the narrow stem of CE in the middle of a large thick disc which is too thick to poke a hole into with a screwdriver. To get at this small stem of explosive he would have to penetrate the metal tin disc that covers the thick disc, once into that the bursting charge but to get into the main charge he would have to penetrate a thick metal cup that holds the bursting charge of the fuze. In operation the det cap bursts into the thin disc to set of the small stem into the next bursting charge. He could have penetrated the tin disc while the det cap was to the side thus revealing the white CE normally light yellow and then disrupted the det cap so it sprang in line with the CE stem so the next time he poked with a screwdriver it set of the det cap.
 
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Thanks for this. In the back of my mind I wondered what caused it to be a blind.

If I get this right; are you saying that the round has a 4-stage detonation process and that the 1st det cap wasn't under the striking pin, thus causing the blind? Can I paraphrase what you wrote and perhaps you can correct me.
The screwdriver was inserted into the sealed tin of the 2nd stage fuse. He punctured this tin and white/yellow powder came out. For this white powder to come out, he obviously withdrew his screwdriver. When he inserted the screwdriver again the 1st det cap had somehow moved into its correct position over the punctured tin disc and oblivion...
Kind regards,
Rondee.
 
I am only assuming what could have happened, the mortar round could have grazed a bush so the wind shield is not crushed enough for the striker to set off the det cap. When you mention the sealed tin i mean a tin disc that sits onto of the thicker metal disc with a small hole in the middle that contains a small amount of CE the septum. To get at the white powder you mention, this small round hole would be the only way for such a substance to come out, hence the det cap that would be in its way, if the striker and det cap worked properly ie moving in alignment, so it would seem the det cap was to the side jammed in place until the boy dislodged it and then poke the screw driver in.. Not that you may not want to, it would be best to examine a deactivated one close up rather than a drawing as then it would make sense what could have happened.
 
What you say makes good sense. There's some evidence in the coroner's inquiry that a mortar blind was found in a river. The area was also covered in thick gorse and bracken. The 2" mortar has quite an ingenious fuse mechanism. I'm afraid I know nothing about why it needed a 4-stage detonation process.
 
First the cap is set off by the striker 1, which sets off the septum 2 which then sets off the CE pellet 3 which exploded into the main charge 4 setting that off. You need a detonation to detonate explosives, a simple det cap won’t do this.
On a WP round there is no main charge just a small sealed tin can of white phosphorus, which is activated when exposed to air by the exploding CE pellet. The CE pellet when it is set off is powerful enough to blast open the bomb casing and tin like a split banana spreading WP all around. The CE pellet alone would kill or seriously injure you without any additional explosives. A live fuze alone is a dangerous thing. I do have a picture of the remains of a exploded WP case which the CE pellet alone caused, so you can see the destruction it would cause to finger arms etc.
 

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I'm having an education!! Thank you so much for this. There's one other aspect of the fuse I need help and it's the type of HE mortar that was tampered with on March 1945.

I have a diagram of the Mk 1 161 and it shows a hole to the left of the striker that has unimpeded access to the det cap directly below but other types have this hole blocked off. (I'm sorry I can't insert a picture?) Would you have any idea as to the type of mortar that would be used in training in March 1945 that have this hole open or closed.
 
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