8,8 cm PzGr 39 Performance

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Mobius
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 23 Dec 2018 17:59

Miles Krogfus wrote:
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 . . .
One of the 100mm penetration tables for the DDR for 1960s was slightly different than the standard Russian of the same guns. Did they use a different K factor?

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Re: 8,8 cm PzGr 39 Performance

Post by Miles Krogfus » 24 Dec 2018 02:04

No other 100 mm AP and APBC K factor is stated as being used for the creation of armor plate penetration figures in any Russian or Soviet bloc FT!

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 24 Dec 2018 14:34

Miles Krogfus wrote:
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 . . .
The 76.2mm BR-350 on these captured firing tables seems to defy a consistant K-factor.
https://digitalcommons.unl.edu/dodmilintel/66/
Neither K=2400 or K=2450 seems to work.

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 24 Dec 2018 16:02

Mobius wrote:
24 Dec 2018 14:34
Miles Krogfus wrote:
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 . . .
The 76.2mm BR-350 on these captured firing tables seems to defy a consistant K-factor.
https://digitalcommons.unl.edu/dodmilintel/66/
Neither K=2400 or K=2450 seems to work.
The velocity/penetration is a good match for values of ( D=0,76; W=6,3; K=2450 ). It's not a perfect fit, but the small difference is probably just the rounding errors. Remember that at the time they had to do these calculations by hand.
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Re: 8,8 cm PzGr 39 Performance

Post by Miles Krogfus » 24 Dec 2018 17:06

Check the page from my article posted above by Peasant. The K for BR 350 is 2550, weight of 6.5 Kg. I have FT data for all the 76.2 projectiles used in WW II. The BR 350 FT differs from the A and B. The BR 350A is 6.3 Kg the B 6.5 Kg.

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 24 Dec 2018 18:54

Peasant wrote:
24 Dec 2018 16:02
Mobius wrote:
24 Dec 2018 14:34
Miles Krogfus wrote:
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 . . .
The 76.2mm BR-350 on these captured firing tables seems to defy a consistant K-factor.
https://digitalcommons.unl.edu/dodmilintel/66/
Neither K=2400 or K=2450 seems to work.
The velocity/penetration is a good match for values of ( D=0,76; W=6,3; K=2450 ). It's not a perfect fit, but the small difference is probably just the rounding errors. Remember that at the time they had to do these calculations by hand.
I was using the 6.48-6.51 kg. of the US writeups on these shells. If they are 6.3 kg then it works.
I made a little program tool to calculate Russian demarre
http://panzer-war.com/Files/redstardemarre.zip

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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 25 Dec 2018 01:52

Miles Krogfus wrote:
24 Dec 2018 17:06
Check the page from my article posted above by Peasant. The K for BR 350 is 2550, weight of 6.5 Kg. I have FT data for all the 76.2 projectiles used in WW II. The BR 350 FT differs from the A and B. The BR 350A is 6.3 Kg the B 6.5 Kg.
AFAIK there were two main designs of projectile used in soviet 76mm guns. BR-350A and BR-350B. But what's this BR-350 projectile? It looks like the conflagration of both A and B versions, which could happen if the BR-350A was first called simply BR-350 and obtained the "-A" suffix only after the introduction of the "-B" version, but western intelligence didnt realize the distinction at first and for some time been calling both just BR-350. mixing the data between the projectiles.

Attached are the designs of both projectiles(for reference).

Edit: Btw, we are getting seriously offtopic here.
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 25 Dec 2018 02:12

This is what I have:
76mmBR-350x.jpg
The Br-350B variant looks like it has a larger cavity than the BR-350B. So that may be a BR-350B1 and the other a BR-350B2 (small cavity).
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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 25 Dec 2018 16:13

whelm wrote:
22 May 2018 19:40
Image
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
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Re: 8,8 cm PzGr 39 Performance

Post by whelm » 25 Dec 2018 19:30

Image

Image

Image

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 25 Dec 2018 20:57

Thanks whelm.

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 26 Dec 2018 15:49

The APCBC 6pdr has the best ballistics of the bunch of BC capped similar size AP shells. (If it is being calculated correctly.)
57mm BC strikingj.jpg
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Re: 8,8 cm PzGr 39 Performance

Post by Peasant » 26 Dec 2018 22:30

Mobius wrote:
26 Dec 2018 15:49
The APCBC 6pdr has the best ballistics of the bunch of BC capped similar size AP shells. (If it is being calculated correctly.)
Something to be aware of when measuring S.V. and Penetration from these tables: the image is distorted, so that two parallel lines on a grid do not remain such along upper and lower/ leftmost and right most edges of the chart. Its not simply rotated one way or another so you cant compensate by rotating and/or traslating the image in photoshop.
The only way I've found to be able to get relatively accurate measurements is to do it at one block at a time, then realign the grid at the new one.
I'll post the results if anyone wants them.
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Re: 8,8 cm PzGr 39 Performance

Post by whelm » 26 Dec 2018 22:54

some estimated numbers comparing the 6 pdr canuck's apcbc

Image

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Re: 8,8 cm PzGr 39 Performance

Post by Mobius » 27 Dec 2018 00:20

Peasant wrote:
26 Dec 2018 22:30
Mobius wrote:
26 Dec 2018 15:49
The APCBC 6pdr has the best ballistics of the bunch of BC capped similar size AP shells. (If it is being calculated correctly.)
Something to be aware of when measuring S.V. and Penetration from these tables: the image is distorted, so that two parallel lines on a grid do not remain such along upper and lower/ leftmost and right most edges of the chart. Its not simply rotated one way or another so you cant compensate by rotating and/or traslating the image in photoshop.
The only way I've found to be able to get relatively accurate measurements is to do it at one block at a time, then realign the grid at the new one.
I'll post the results if anyone wants them.
Right, I had use the range tics and count pixels between Strike velocity lines.
6 pdr apcbcj.jpg
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