8,8 cm PzGr 39 Performance

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critical mass
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Re: 8,8 cm PzGr 39 Performance

Post by critical mass » 21 Dec 2018 12:56

I am pretty sure the GDR had to go with whatever the soviet authorities, commanding the warsaw pact armies passed on to them for service instruction.
They were not allowed to conduct their independent R&D.

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Mobius
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 21 Dec 2018 15:24

critical mass wrote:
21 Dec 2018 12:56
I am pretty sure the GDR had to go with whatever the soviet authorities, commanding the warsaw pact armies passed on to them for service instruction.
They were not allowed to conduct their independent R&D.
Of course. As some GDR penetration tables were copies of their Russian commanders. But then there were GDR versions of the same that where different. And the Yugoslavs and Hungarians did some testing of Russian weapons.

critical mass
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Re: 8,8 cm PzGr 39 Performance

Post by critical mass » 21 Dec 2018 16:21

Fair enough. Though I am not convinced the differences are because they had accumulated generic, independent data on them. They might just as easily derive from newer, and thus compared to ww2 vintage quite different testing procedures, target hardness materials, etc. employed in updated standartization trials conducted by the USSR.

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 21 Dec 2018 16:25

For example here is a Hungarian firing table for the Russian 57mm.
Hungarianarchive57mm.jpg
You can find the Russian version many places.
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peeved
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Re: 8,8 cm PzGr 39 Performance

Post by peeved » 21 Dec 2018 17:59

According to Google Translate: Megjegyzés: a páncélatütés adatai az 1945-ben kiadótt 0316 számú szovjet táblázatból valók. = Note: Armor information is from Soviet table 0316 issued in 1945.

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Mobius
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 21 Dec 2018 18:34

I guess the Russians revised their K=2400 table.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 22 Dec 2018 02:27

I'd like to point out that those new penetration values for BR-271@90° cannot be obtained by fitting the K constant in ARTKOM's DeMarre formula.
The most likely explanation I see: this data is re-calculated using updated external ballistics tables.

critical mass
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Re: 8,8 cm PzGr 39 Performance

Post by critical mass » 22 Dec 2018 15:30

I don´t see the problem here.

0,57dm cal
3.14 kg weight
1.14dm plate thickness
K=2400

necessary velocity: 973.8m/s

Since the muzzle velocity of the 57mm ZiS-2 is 1000m/s, a penetration of 114mm (high hardness) armor at vertical and 100m range is feasable using a De Marre K = 2400.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 22 Dec 2018 16:53

No, i'm taking into account the penetration at all ranges. Varying the K constant just traslates the curve up and down without changing its shape. The only way the relationship between penetration(ergo:terminal velocity velocity) and range could change, if they used different ballistic tables to calculate them. Now whether its the result of a more accurate external ballistics model or a new windshield design, the Hungarian table indicates that its loosing its velocity/pen faster than before.
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critical mass
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Re: 8,8 cm PzGr 39 Performance

Post by critical mass » 22 Dec 2018 18:08

Thanks for explenation. Yes, different terminal ballistic conditions seems to be the most likely cause for this variance.

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Mobius
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 22 Dec 2018 18:15

critical mass wrote:
22 Dec 2018 18:08
Thanks for explenation. Yes, different terminal ballistic conditions seems to be the most likely cause for this variance.
I don't have the ballistics from a firing table for the BR-271 @ 990 m/s. But it probably similar to that of the US 57mm M86 or British 6pdr APCBC.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 22 Dec 2018 19:39

Me neither. You can extrapolate the terminal velocities at various ranges from the penetration numbers given, with the formula used to calculate them in the first place.

Edit: Of course, keeping in mind that those tables are not always free of errors.
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 22 Dec 2018 22:04

Solving for V I found the Russian 57 APBC slope gives a ballistic coefficient very close to the US 57mm M86 shell.

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 23 Dec 2018 03:29

So this Is what I get when I plot these out. Both Russian and Hungarian data is K=2400. Anything else is inconsistent with the MV.
57mmguns.jpg
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Re: 8,8 cm PzGr 39 Performance

Post by Miles Krogfus » 23 Dec 2018 04:47

For example, the 76.2 mm AP rating went to K=2450 for the BR 350 A then K=2400 for the BR 350 B. This figure remained for all mm of AP and APBC projectiles for the rest of WW II. All Soviet Firing Tables had flaws relating to velocities and thus penetration down range figures, like the 122 mm that I have posted at AHF about so that Russian conducted penetration tests against armor plate have consistent at range success errors. During the war, the down range FT velocities of the BR 350 B were listed as the same as that of the BR 350 A . . .

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