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Settle a bt...EOD guys.....Would Pzgr 39....

L

lc123

Member
I have a bet regarding 7,5 cm Pzgr 39 (any type) actually fragmenting after piercing armor intact. By that, I mean, if a penetrating round, that initiates its small 17 gram HE charge, actually fragment? I say such a small charge would just blow out the threaded tracer. Make a big bang. I have seen what seems to be images and video of US troops pulling out spent ammunition from penetrated Shermans and even destroyed Panthers that have cooked off some rounds inside. Basically just the caps are gone and the penetrator is seen with a cavity at the back. I would imagine if a round that penetrates, and might have cracks, could break up into a few chunks, but we are talking about the whole rear half of the AP 'grenading'...thoughts?
 
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Yes it fragments but the front part not always. Keep in mind that the shells are brittle because they are hardened until 58 HRC and the HE charge consists of very powerful Hexogen. The front part is the hardest part and the base the softest. Small failures in heat treatment and such shells "fragment" (break) upon impact on a armor plate even without a HE charge. Because such broken shells don't penetrate much armor long tests with thousands of fired shells were carried out to find the best method of heat treatment and the best steel alloy without using rare elements like Cobalt, Molybdenum or Vanadium because they didn't had enough of these metals during war.
 
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Alpini said:
Yes it fragments but the front part not always. Keep in mind that the shells are brittle because they are hardened until 58 HRC and the HE charge consists of very powerful Hexogen. The front part is the hardest part and the base the softest. Small failures in heat treatment and such shells "fragment" (break) upon impact on a armor plate even without a HE charge. Because such broken shells don't penetrate much armor long tests with thousands of fired shells were carried out to find the best method of heat treatment and the best steel alloy without using rare elements like Cobalt, Molybdenum or Vanadium because they didn't had enough of these metals during war.
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i think you are disregarding the softest part...that is the rear tracer/fuse element? In any case, this somewhat well known image shows 5,0 cm penetrators stuck in the armor. Clearly, the negative acceleration has triggered the fuse, and the detonation has left, what I have described?

https://external-content.duckduckgo.com/iu/?u=http://i.imgur.com/JY8GgpZ.jpg&f=1&nofb=1

kv1.jpg
 
This image shows a US serviceman examining two recovered penetrators. These are actually the 'bolts' or main penetrator, without any caps. They evidently lost in the event. Note neither shows any loss of mass from the small 17 gm HE charge inside. i suspect these are 7,5 cm Panther rounds.

75cmpantpensherm.jpg
 
I have seen these pictures before but I am not sure if anything is known about them. Do you know more of their background? There are many possibilities why they are as they are. Low quality explosive from 1945, unfilled TP shells, wrong heat treatment, etc.

I may be wrong but both do not look like battle damaged. The hits came exactly from the same angle and they are very close together.

Complete or half front parts of 7,5 / 7,62 cm Pzgr 39 which missed the target and detonated correctly are found from time to time by metal-detectorist in my country.

EOD destroyed Pzgr. 39 (using a shaped charge) often show the effect of blown out fuzes like you mention (also for 8,8 cm PzGr). I have been told it's because of deflagration of the HE charge. Sometimes these shells also break into two halves like sections.

The shells in the last picture have only one driving band so they can't be from a 7,5 cm KwK42 of the Panther. More likely from 7,5 or 7,62 cm Pak or any of the other guns.
 
Personally I think the charge was not meant to splinter the projectile as such, but augment/enhance the effect of an already weakned/cracked penetrator body.
On impact the ballistic cap and penetrator cap take the first blows, dissipating a lot of energy away from the hardened penetrator nose. However on it's way through the armour, the penetrator will inevetably develop cracks and splinters. I believe that the small charge detonated with a short delay, will boost the velocity of the parts/splinters. Imagine the hardned nose penetrating and reaching target's innerside, when, with a major part of the projectile body still inside the penetration channel, the charge detonates. The body can't expand (much) "captured" in the channel, thus detonation is sent via the (cracked) nose/upper body. I can see this acting very "shotgun like". Especially as the weak thread holding the basefuze, should, by that instance, be more resillient than the cracked nose/upper projectile body.
It would be very informative (and equally disturbing) to see pictures of the insides of allied armour hit, in combat, by "39"
 
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What puzzles me, are the many reports of German AP pentrating a target one side and exiting on the other. As the vast majority of German AP, either 7,5 or 8,8, was of the "39" (APCBC-HE-T) type, how come so many failed to detonate? I am not willing to accept "must have been "40" (APCRHC) than", as that ammo was quite scarce and was reserved for the heaviest of targets (not to be spent on the ubiqutous M4). With the event of the Bd.Z.5127 duds would seem even more unlikely
 
pzgr40/42 said:
What puzzles me, are the many reports of German AP pentrating a target one side and exiting on the other. As the vast majority of German AP, either 7,5 or 8,8, was of the "39" (APCBC-HE-T) type, how come so many failed to detonate? I am not willing to accept "must have been "40" (APCRHC) than", as that ammo was quite scarce and was reserved for the heaviest of targets (not to be spent on the ubiqutous M4). With the event of the Bd.Z.5127 duds would seem even more unlikely
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Fuse failures are an interesting subject here. In bombs you're looking at ~10% of fuses are never going to trigger. Even modern rounds are effected, I saw a report that said 40mm grenade launcher rounds are about ~8% fuse failures. It would logically then follow that if 10% are insensitive, then the same number would be hyper sensitive. Suddenly you're looking at 20% of your rounds fired not acting as advertised. You can see why some nations just said 'Sod it, lets fire solid shot'. I'll bet there's some interesting reports on this kicking about in archives.
 
I recall reading an account of a Sherman being penetrated and the round bouncing around the inside, spinning like a top and spitting out flames from the tracer. It has been a long time since I read that, and I do not recall any of the more recent first person Allied tanker books having such an account. Most were just heard a bang, fire and get out.
 
pzgr40/42 said:
What puzzles me, are the many reports of German AP pentrating a target one side and exiting on the other. As the vast majority of German AP, either 7,5 or 8,8, was of the "39" (APCBC-HE-T) type, how come so many failed to detonate? I am not willing to accept "must have been "40" (APCRHC) than", as that ammo was quite scarce and was reserved for the heaviest of targets (not to be spent on the ubiqutous M4). With the event of the Bd.Z.5127 duds would seem even more unlikely
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The Germans knew that sloped armor resulted in many fuse failures after penetration. This is due to the rear of the projectile gets 'slapped' as it turns into the sloped armor. The 17 gm explosive was considered by the Germans to be enough to incapacitate a buttoned up crew.
 
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