Prematures

[Matlock1418]

I can sort of perhaps understand what might cause a 'dud' - poor fuses/settings, duff bursting & explosive charges I guess [always open to further enlightenment on this too]

 

But what might cause a 'premature'?

- Shells

- Bombs

- Grenades (hand and rifle)

i.e. going off much sooner than intended  [i.e. in barrel or shortly after - not just dropping/not throwing quickly enough after a flyoff lever had gone from a grenade]

I'm again guessing iffy fuses/fusing and charges etc. - but hope you good sorts can enlighten me further/more accurately please

???

Thanks in anticipation.

:-) M

[Gunner Bailey]

Regarding grenades the Mills No 5 suffered from premature detonation for two reasons, defective levers releasing the striker before the grenade was thrown, as a result of poor manufacturing standards but premature detonation mainly was due to the fuze suffering a fast 'burn through' due to a lack of ventilation inside the grenade. The first occurrence of this was on the 30th July 1915 with an 'accident' at Woolwich Arsenal during testing. Mills spent a lot of time right through to the end of 1915 working on it. The answer was the slot being cut into the bottom of the striker which was progressively introduced from 1916 onwards.

 

Regarding rifle grenades the main culprit was the No 22 which had design issues with the cap which was impacted by the .303 cartridge used as a detonator on launch rather than on landing. Two types were used but eventually the No 22 was abandoned in 1917, for the more expensive but reliable No. 24 and the later No. 35. 

[Matlock1418]

Thanks GB,

23 minutes ago, Gunner Bailey said:

Regarding grenades

An interesting start.

 

I have never been a gunner or mortarman, hence my enquiry - Why would a fuse operate early?

 

As for grenade levers and strikers I am presuming it is physical manufacture tolerance that would create the defectiveness and early release/striking.

Or something else?

 

However I can't imagine that fuses would allow for such a setting/immediate activation on/so extremely quickly after firing
I can perhaps understand a slow fuse - presumably a slow train or a complete failure and thence a dud [this is not about shorts - which may or may not function]
Or can you have a fast train too and thus a premature?

 

Thus ...

Whilst not really familiar with grenades and the various No. types mentioned I think I essentially understand your post. 

You mentioned one of my suspects [above] - "fast 'burn through'".

I am curious as to "lack of ventilation" - what does that mean?

More ventilation [as in more air/oxygen] to me means generally means faster combustion so a lack of it has me scratching in this scenario.

I know propellants/explosives have their own oxidising components, but ... ???

I suspect I may have the wrong end of the stick and/or dodgy knowledge and comprehension when it comes to this point about grenades.

 

Always interested in the practical things that affected servicemen's experiences of weapons and munitions, and not just at the intended 'receiving end'.

:-) M

Edited 1 June , 2020 by Matlock1418

[Gunner Bailey]

With the Mills grenade the lever was intended to detach from the striker when the bottom of the lever was 1 1/4" away from the body. Ideally the lever would be gripped tightly to the body up until the grenade left the thrower's hand. It was found though that some soldiers did not grip the grenade tightly enough and where the lever had been badly manufactured the striker was allowed to drop whilst the grenade was still in the throwers hand. Exploding the grenade before it was thrown. 

 

For the Mills grenade the fuze was enclosed under the centre piece with no clear air flow. I can't explain the science of fast burn through but adequate air allowed the fuze to burn as intended. Bickford invented his rope fuze to be reliable and to burn at a known rate to make mining work safer. Bickford's rate was 30 seconds for a foot of fuze. Not giving the fuze adequate air flow made it burn faster, indeed almost instantaneous.

[Matlock1418]

20 minutes ago, Gunner Bailey said:

With the Mills grenade the lever was intended to detach from the striker when the bottom of the lever was 1 1/4" away from the body. Ideally the lever would be gripped tightly to the body up until the grenade left the thrower's hand. It was found though that some soldiers did not grip the grenade tightly enough and where the lever had been badly manufactured the striker was allowed to drop whilst the grenade was still in the throwers hand. Exploding the grenade before it was thrown. 

Lever under fingers could allow a release of lever without conscientious knowledge - hence lever to palm and gripping body of grenade was introduced I believe

20 minutes ago, Gunner Bailey said:

For the Mills grenade the fuze was enclosed under the centre piece with no clear air flow. I can't explain the science of fast burn through but adequate air allowed the fuze to burn as intended. Bickford invented his rope fuze to be reliable and to burn at a known rate to make mining work safer. Bickford's rate was 30 seconds for a foot of fuze. Not giving the fuze adequate air flow made it burn faster, indeed almost instantaneous.

Hmm?

Wonderful thing science - if you understand it, and I'm struggling here.

[Mods: I'm not making a current political statement! - it''s thread topic-related]

Edit: I wonder if it is due to the pressure build-up/increased heat transfer or even increased heat of a limited ventilated burn?

???

Edited 1 June , 2020 by Matlock1418
addition

[14276265]

The No.3 rifle grenade and its simplified successor the No.20 were blighted with prematures. After many trials over several months, a fault was found in the detonator pellet, which when rectified effectively solved the problem.

 

The No.3 detonator flaw was similar to that encountered in certain of the early percussion fuzes for HE shell, where some tiny part of the detonator pellet set back on firing - this lead to a whole tranch of development work to provide safety devices (detents and shutters).

 

 

 

265

[Gunner Bailey]

We're there ever numbers linked to Early Hale's prematures Tom? Volumes were never massive in usage. 

[Matlock1418]

19 hours ago, 14276265 said:

some tiny part of the detonator pellet set back on firing

Trying to keep up with others who know a great deal more than me.

What is this "set back"?

Is it a movement of a physical part or a compression of filling on firing?

Or ???

And, how did it thus cause a premature?

[I'm currently hypothesising that a compressed/compacted detonator filling might have a greater/faster burn rate compared to less-compacted ???} Edit: Now explained below

:-) M

Edited 2 June , 2020 by Matlock1418

[Gunner Bailey]

Here's quite a good diagram that shows the No 24.

 

When the pin was removed and the grenade fired, Inertia moved the 'set back collar' (releasing socket on this diagram) backwards freeing the two 'retaining bolts' which fell away. This freed the striker to move forwards when it hit the ground / target. It would compress the creep spring by force allowing the pin on the end of the striker to hit the detonator. The creep spring was there so that if the grenade was dropped accidently after the pin was removed the spring would stop the striker hitting the detonator as the drop was insufficient to fully compress the spring.

 

In the No. 3 the bolts were held in place by a wind vane that on firing wound back with the airflow and then released the retaining bolts.

 

Edited 1 June , 2020 by Gunner Bailey
expanded answer

[Matlock1418]

36 minutes ago, Gunner Bailey said:

the 'set back collar' (releasing socket on this diagram)

Thanks for your recent post.

 

I have been doing a bit of reading in the interim:

HAND GRENADES
A HANDBOOK ON RIFLE
AND HAND GRENADES

COMPILED AND ILLUSTRATED BY

Major GRAHAM M. AINSLIE

FIRST EDITION

NEW YORK

JOHN WILEY & SONS, Inc.

London: CHAPMAN & HALL, Limited
1917

https://www.gutenberg.org/files/56638/56638-h/56638-h.htm

 

Now I know what I am looking for I note the releasing socket on a No 20 on page 25

 

I also noted on pages 10 [No 5] and 58 the use of fingers holding the lever - not what I understood was the correct way- or was using the palm a later development?

 

One of my previously un-posted questions was:

Does shock of firing have some impact on artillery, mortar and/or rifle grenade fuses [presumably likely both delayed and impact ones] and/or other charges?

 

3 hours ago, 14276265 said:

some tiny part of the detonator pellet set back on firing

As for 'set back' here I am starting to think a small fragment broke off and detonated setting of the whole thing as a premature.

Am I on the right track?

 

Happy to hear more on premature grenades - Interested as a family member, who survived, was trained as a rifle-bomber [though know that could mean a rifleman with Mills bombs, but perhaps also rifle grenades ??? - or were those called rifle grenadiers?] - he went on to be a runner.  I don't know which was the more dangerous!

 

And about premature artillery shells and mortar bombs of course.

:-) M

[14276265]

4 hours ago, Matlock1418 said:

What is this "set back"?

Is it a movement of a physical part or a compression of filling on firing?

Or ???

And, how did it thus cause a premature?

 

 

The shock of discharge of a projectile causes any component that is unrestrained to appear to fly back towards the gun. In reality the component is momentarily stationary as the rest of the projectile accelerates forwards. The action is referred to as set-back.

 

In the case of the No.3 and No.20 rifle grenade fuzes, the detonator was initiated by a small 3-grain percussion cap. The construction of the cap used two small foil discs, one of which was found susceptible to set back into the cap body on firing the rifle, causing the cap to explode and setting of the detonator. Changing the way the caps were manufactured, and finally choosing a simpler design of cap, solved the issue of prematures with these troublesome grenades.

 

Detonator cap failure in early percussion fuze designs for artillery was just one of several faults that were identified as causing prematures.

[Matlock1418]

6 minutes ago, 14276265 said:

The shock of discharge of a projectile causes any component that is unrestrained to appear to fly back towards the gun. In reality the component is momentarily stationary as the rest of the projectile accelerates forwards. The action is referred to as set-back.

Thanks for the clarifying explanation.

7 minutes ago, 14276265 said:

In the case of the No.3 and No.20 rifle grenade fuzes, the detonator was initiated by a small 3-grain percussion cap. The construction of the cap used two small foil discs, one of which was found susceptible to set back into the cap body on firing the rifle, causing the cap to explode and setting of the detonator.

I can see how that would be a problem!

:-) M

[Gunner Bailey]

12 hours ago, 14276265 said:

 

In the case of the No.3 and No.20 rifle grenade fuzes, the detonator was initiated by a small 3-grain percussion cap. The construction of the cap used two small foil discs, one of which was found susceptible to set back into the cap body on firing the rifle, causing the cap to explode and setting of the detonator. Changing the way the caps were manufactured, and finally choosing a simpler design of cap, solved the issue of prematures with these troublesome grenades.

 

Detonator cap failure in early percussion fuze designs for artillery was just one of several faults that were identified as causing prematures.

 

So to be fair the Frederick Marten Hale it was detonator design rather than the design of the grenade?

[14276265]

The detonator was an integral part of the grenade and had originated with Hale. Early in 1915 a lack of co-operation by Hale's company, Cotton Powder Co, in expanding production of the detonator was in part the reason for Hale's attitude being noted officially as "inexplicably unsatisfactory".

 

As for the No.3 grenade, in early 1916 over a third were failing at proof (some prematures, most blinds) but the need was so desperate they were accepted. Ironically Hale pulled out of contracts for the No.3 as being too difficult to make without incurring an unacceptable amount of rejects; he had moved to the company of Roberite and Ammonal from which nearly two thirds of the output failed at proof. Thereafter redesign of Hale type grenades to reduce the percentage of blinds and prematures was passed to one of his competitors, all a fun part of the story of WWI British rifle grenades.

Edited 2 June , 2020 by 14276265

[new3.2]

Back to artillery- I have had two prematures in the bore shooting a US 3.2"  Span/AM era cannon.  Both times we think it was caused by casting flaws in the zinc projectile.  There is a bit of excitement  as parts of the projectile go down range as cannister rounds do, kicking up much dust, and rattleing around generally. .  The tube is cast steel (1898) and the gun was not harmed in any way.
new3.2

[Matlock1418]

8 hours ago, new3.2 said:

Back to artillery

Thank you - an area not yet explored  :-)

 

Still also looking for mortar stuff too - Know I have seen a photo of a mortar being fired from a dug-out using a lanyard [a 'toffee apple' bomb I think i recall] - Would that because of the fear of a premature? I've always assumed it was [always the risk of ass u me - or perhaps just because of shrapnel and the like flying around outside?]  - Your thoughts on mortars please

 

8 hours ago, new3.2 said:

I have had two prematures in the bore shooting a US 3.2"  Span/AM era cannon.  Both times we think it was caused by casting flaws in the zinc projectile.  There is a bit of excitement  as parts of the projectile go down range as cannister rounds do, kicking up much dust, and rattleing around generally. .  The tube is cast steel (1898) and the gun was not harmed in any way.

And ... Has brought us to a question I was yet to ask - Which is worse; a 'premature' in receiver, bore or just after left muzzle? [know it is possible for early detonation longer into flight or detonation due to being struck by another projectile whilst in flight - but I am thinking of close to the firer and not rather closer to the intended recipient]

 

Some thoughts / observations from a definite non-gunner:

Your round was zinc in steel barrel = zinc projectiles [and no harm to the stronger/harder gun]

Round with or without an internal charge to compound things? - if with, did it detonate?  [I'm sort of thinking because of your post referring to failure of a casting it did not have / detonate]

I'm presuming that a premature detonation of a WW1 shell charge would be worse than just fragmented inert [but kinetic!] materials from the round.

Can't help but think a WW1 cast [?] iron/steel shell exploding in iron/steel bore would be a very bad situation - potentially extra iron/steel from barrel floating / whizzing around one might presume - but perhaps a bit more directional than one just out of the muzzle [which I presume could also go backwards too]

As for in the receiver - presumably more surrounding metal = ???

So back to that question - Which is worse a premature in receiver, bore or just after left muzzle?

 

As per OP we have so far correctly been looking at premature detonation of a bomb / grenade - but what about potentially 'cooking off' a round/shell/bomb in a weapon's hot receiver [is that just discharging it prematurely (which I understand can happen) or actually detonating it? - or both?]

Aside: And what about variations due to/between cased and bagged/caseless propellants and premature discharges?

I am sure there is much more scope for answers to help me understand prematures [and why you really, really didn't want one in WW1 (and later, and I guess even now)]

:-) M

[new3.2]

My opinion- A pre-mature outside of the muzzle of the tube would be the worst case for hobby folk or in actual battle.  Let me clear some of this by saying that all the live firing that I have been involved with were on military ranges, and we were invited to participate, as giving demonstrations of American Civil War cannon for educational purposes.  Today I know of no military range where this kind of display is allowed.  This all happened during the 70's & 80's.  I was not present at this shoot, but a 10" CW mortar being shot at such a range had a pre-mature above the muzzle and parts of the projectile went all over.  No one was injured.  There is also the propelling charge that tends to aid in having the pieces go down range.  Die-cast or zinc is used to make projectiles because of safety.  All these projectiles were hand cast in molds.  The melting temperature that zinc melts at is about 900 degrees.  zinc also weights the same as the cast iron used in CW projectiles so it is easy to look at the manual to know the correct powder charge.  Cast iron melts about three times as hot as zinc, and that temperature is very dangerous for the hobby casting crew.   The 2-Howitzer (Toffee-Apple) was fired with a friction primer, an ignition devise, quite the same as used in the CW.  The lanyard in field artillery kept the firing person outside of the wheel track of the gun, (recoil) and with the spigot mortar, it keeps him away from the muzzle blast.  Hope I have not gone on to much.

new3.2 

[Matlock1418]

On 14/06/2020 at 01:22, new3.2 said:

The 2-Howitzer (Toffee-Apple) was fired with a friction primer, an ignition devise, quite the same as used in the CW.  The lanyard in field artillery kept the firing person outside of the wheel track of the gun, (recoil) and with the spigot mortar, it keeps him away from the muzzle blast.

Sorry for delayed reply to this other post - thanks.

I till wonder - zinc -v- steel ???

Friction primer - OK think I know a little bit about those so can perhaps see what you mean about lanyard being used

Muzzle blast surely an issue for all mortar weapons - but perhaps the spigot made it worse than the later Stokes [and modern variants of that type]??

 

Also looking for info on artillery prematures - anyone out there who could further help please?

:-) M

Edited 1 July , 2020 by Matlock1418
clarification

[Matlock1418]

On 14/06/2020 at 01:22, new3.2 said:

My opinion- A pre-mature outside of the muzzle of the tube would be the worst case for hobby folk or in actual battle.

Got to admit my thoughts are still 'open' about this - especially if a shell prematurely detonates, but ... ???

Also looking for more info on artillery prematures - anyone out there who could further help please?

:-) M

[new3.2]

I certainly agree with you Matlock, about outside the bore; unless some "Bubba"s decide to use an old gas pipe or some other unsuitable "repro-cannon".

new3.2

[Matlock1418]

Artillery = This thread introduces, in post #5 an interesting explanation for some artillery prematures - hairline cracks [from manufacturing] in shells

:-) M

[KizmeRD]

As regards motars, and specifically German meinenwerfer - the explosive used in the shells was ammonium nitrate-carbon. This was considered an acceptable substitute to use as the muzzle velocity of these weapons tends to be lower than that of conventional artillery (which used a TNT type explosive). However, the sensitivity of the minenwerfer explosive occasionally made it detonate in the tube, and there were many incidences of prematures, one of which claimed the life of the weapon’s designer (Karl Völler of Rheinmetall in 1916).

[squirrel]

Hoist on his own petard...

[trajan]

Shades of the Me263 Komet...

[Matlock1418]

16 hours ago, KizmeRD said:

the sensitivity of the minenwerfer explosive occasionally made it detonate in the tube, and there were many incidences of prematures, one of which claimed the life of the weapon’s designer (Karl Völler of Rheinmetall in 1916).

Many thanks - a useful example to consider

 

13 hours ago, squirrel said:

Hoist on his own petard...

3 hours ago, trajan said:

Shades of the Me263 Komet...

Yes, can see where you are both coming from, but both different types of weapons - and ...please [and I know there has also been a previous reference(s) to the US CW which slipped by], please let's keep on topic / in period lest the mods are overly-distressed and lock my thread! 

Thanks for your anticipated cooperation [and hopefully more contributions]

:-) M