8,8 cm PzGr 39 Performance

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Re: 8,8 cm PzGr 39 Performance

Post by Contender » 09 Sep 2020 10:57

Peasant wrote:
07 Sep 2020 12:10
Wow, what's this: 780m/s velocity for the AP shell? Interesting. Then perhaps the much quoted figure of 773m/s is the velocity at 100m after all.
Image
critical mass wrote:
08 Sep 2020 18:13
soft iron, yes
Interesting I was not aware they made a soft iron core round for the 88 mm caliber.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 09 Sep 2020 13:51

I've cleaned it up a bit.
P.S. The ballistics of this shell are not the same as those of the normal 8.8cm PzGr.39-1. It has slightly more drag.
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Last edited by Peasant on 10 Sep 2020 10:58, edited 3 times in total.

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 09 Sep 2020 22:31

Peasant wrote:
09 Sep 2020 13:51
I've cleaned it up a bit.
P.S. The ballistics of this shell are not the same as those of the normal 8.8cm PzGr.39-1. It has slightly more drag.
You have different firing table? This is the same as the one Mile posted .

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Re: 8,8 cm PzGr 39 Performance

Post by Yoozername » 09 Sep 2020 23:10

I doubt that neither 8,8 cm HL or 'W' rounds were fielded in any great numbers (if ever). The Kursk ammunition consumption posted by Miles seems to reflect that. I have never heard of a W round for this caliber either.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 10 Sep 2020 10:56

Mobius wrote:
09 Sep 2020 22:31
Peasant wrote:
09 Sep 2020 13:51
I've cleaned it up a bit.
P.S. The ballistics of this shell are not the same as those of the normal 8.8cm PzGr.39-1. It has slightly more drag.
You have different firing table? This is the same as the one Mile posted .
Nope, sorry, I was looking at the data I've extracted from FT for the 88mm L/71 gun. But this makes me consider the fact that a, pretty much the same, shell fired from a different gun can have different ballistic profile. Probably something to do with the amount of yaw and the spin imparted to the shell.
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Re: 8,8 cm PzGr 39 Performance

Post by Thoddy » 13 Oct 2020 09:15

"Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!"

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Re: 8,8 cm PzGr 39 Performance

Post by Thoddy » 14 Oct 2020 09:35

Contender wrote: » 08 Sep 2020, 09:01
is Pzgr 40(w) iron-core?
critical mass wrote:
08 Sep 2020 18:13
soft iron, yes
Can you check this, maybe (W) refers to "Wolfram Hartkern"
"Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!"

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Re: 8,8 cm PzGr 39 Performance

Post by Thoddy » 14 Oct 2020 12:11

Peasant wrote:
04 Mar 2019 15:03
Mobius wrote:
25 Dec 2018 16:13
Whelm. do you have any British Critical Velocity charts on the ballistic capped British 6 pdr? It would be interesting to compare it's ballistics with that of the Russian 57mm and US 57mm M86.

BTW, plotting 88mm MV=780 m/s velocities on the British CV of 88mm small capacity yields these data points.
88mmsmallcapcityOB44.jpg
Mobius, I have good news. we can stop pixel-hunting on these charts. These curves were computed using this formula here:

Image

Image

With n = 1,43, as the later paper suggests, the R constant is very close to 3260, for 6pdr AP at normal incidence (SD=27)
Here is the calculated graph from excel overlayed on top of the chart:

Image

To get R not so small as to go into decimal values, I've used Kg for shell weight, cm for diameter and m/s for velocity.
Other charts will have slightly different "R"s, mind you.
Hello Peasant,
is it possible to provide the converted Excel -Gercke Formula
as well as Thompson F-Formula and de Marre

:idea:
Thank you in advance
"Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!"

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 14 Oct 2020 18:43

Thoddy wrote:
14 Oct 2020 12:11

Hello Peasant,
is it possible to provide the converted Excel -Gercke Formula
as well as Thompson F-Formula and de Marre

:idea:
Thank you in advance
I'm afraid I dont understand what you're asking me to do, can you explain that in more detail?

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Re: 8,8 cm PzGr 39 Performance

Post by Thoddy » 15 Oct 2020 06:51

You wrote
"Mobius, I have good news. we can stop pixel-hunting on these charts. These curves were computed using this formula here:"
...
I concluded you had derived the formula for use in Excel as well as the de Marre and Thompson formulas.
I tried it also but failed.


May you can copy the pieces to the forum? or in a PN.

Thorsten
"Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!"

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Re: 8,8 cm PzGr 39 Performance

Post by critical mass » 15 Oct 2020 10:43

Thoddy,
Pzgr.40 designations:

Pzgr.40(Hk.) -tungsten carbide cored and uranium cored projectiles (Hartkern)
Pzgr.40(St.) -hardened steel cored (Stahl)
Pzgr. 40(W) -soft iron (Weicheisen)

The Pzgr.40(W) was a blunt nosed APBC-shot, matched ballistically to Pzgr 40. It had a ballistic cap to retain downrange velocity but no armor-piercing cap, fuse or filler due to it´s assumed plastic deformation on impact (see attachment for the schematic of the 75mm Pzgr.40(W)). The projectile body received not the usual differential hardening treatment either. Projectiles such as those would not be capable of attacking the target plates resistence to ductile holing, unless its highly overmatched. It couldn´t penetrate a strong enough plate intact and even against thin plates deforms to cover a wider area on the impacted point, hoperfully overcoming the target plates shear strength (target plate failing at once with discing and scabbing primarely). The very short and blunt projectile body assists in negotiating high obliquity effects. Not too dissimilar to post ww2 HESH but of course without the added explosive effect of the high explosive. In my opinion, at short range (i.e. high velocity) it should be somewhat effective versus oblique and high hardness armor plate, in the range of 0.4-0.6 cal/D, perhaps slightly more, depending on target plate shear toughness (the harder the target plate, the more effective this attack will be). It´s function within target rests purely on kinetic impact effects, aided by it´s and the target plates fragmentation damage. A base fuse and high explosive element would not work here because it could explode the projectile before perforation or holing was obtained.

If You plot the performance vs obliquity it would result in a very flat curve with low obliquity effects. Quiete unlike the Pzgr40(Hk.), which didn´t like high obliquities. But in turn, the Pzgr.40(W) must have been awefully impotent against thick vertical armor plate (1cal/D or more), which would just smash the projectile body (upset failure). This is not a good performance, its an intentionally capped performance but allows the ballistic advantages of light weight and high i.V.

There was also a Pzgr41(W) for the 75mm PAK41 (see attachment)
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Re: 8,8 cm PzGr 39 Performance

Post by Contender » 15 Oct 2020 19:03

I thought Uranium core was "suggested" by some sources but never proven.
The Panzer Beschuss tafel for the Pak 41:
Image
Image
Image

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Re: 8,8 cm PzGr 39 Performance

Post by critical mass » 16 Oct 2020 13:28

See attachment of summery of notes on ammunition development (spefically 37222/43, orginally classified SECRET, dated 13th of august 1943). I was only referring to designations. Uranium cored ammunition would be included in the Hk.-category. by inference from this source. A Führerbefehl requiring a substantial enlargement of uranium processing capacity for the explicit purpose of manufacturing uranium cored Hk. ammunition implies that at least some experimental work had been concluded with some form of projectile by this date. I am not informed about the results of these experiments. It does not mean that uranium cored ammunition was actually procured, of course.
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Re: 8,8 cm PzGr 39 Performance

Post by Contender » 16 Oct 2020 21:56

ty for information.
Last image on my previous post (apologies the image looks a bit small) open imagine in new tab for larger pic or save image as.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 17 Oct 2020 13:14

Thoddy wrote:
15 Oct 2020 06:51
You wrote
"Mobius, I have good news. we can stop pixel-hunting on these charts. These curves were computed using this formula here:"
...
I concluded you had derived the formula for use in Excel as well as the de Marre and Thompson formulas.
I tried it also but failed.


May you can copy the pieces to the forum? or in a PN.

Thorsten
Alright I think I understand what you mean.

Take for example this chart here for 6pdr shot: https://i.imgur.com/Oyy1r7s.jpg

You can calculate with extremely high accuracy the relationship between thickness and critical velocity for perforation with this formula:
Image

or the same in explicit form relative to V:

Image

Using K = 1807 and n = 1,43

I went into more details DeMarre and similar formulas here: viewtopic.php?p=2282814#p2282814

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