Soviet Tests: Guns, Ballistic Trials...

[Mobius]

In trying to normaize this data to agree with other data I have gathered I found a possible error in labeling the data from The Russian Battlefield. They have table CP data the BR-471 and the BR-471B. But pluging in their BR-471 data into my curve fit program and it looks like this might be for a BR-471B round. Compare it to DDR data of both rounds it can be seen that this round does not lose velocity like the BR-471.

Edited September 5, 2012 by Mobius

[alejandro_]

Very interesting Mobius. I will try to find when when the tests carried out, and if they were done at different times. I do not think BR-471B was available in 1943. AFAIK trials were carried out in 1944 and round began to be deployed in early 45.

[Mobius]

Very interesting Mobius. I will try to find when when the tests carried out, and if they were done at different times. I do not think BR-471B was available in 1943. AFAIK trials were carried out in 1944 and round began to be deployed in early 45.

Hey alejandro, I think I saw one of your old (2008) posts on ww2aircraft forum where you were posting discussion with someone called Soren. (BTW, where I found the 122mm DDR firing table data.) Did someone have Aberdeen data on the 88/L71 or was that just Rexford's WW2 Ballistics data?

[Marek Tucan]

Question: If I have a penetration curve done by, say, US standards and want to convert it to, say, Soviet standard (providing I have one data point), is it as simple (for general impression) as simply using the same coefficient for all values, IE moving the entire curve up or down?

 

Example: I have US curve of say 100mm/100m; 80mm/500m; 60mm/1000m and a Soviet test giving say 90mm/100m, so can I then go with 0.9*80=72mm/500m and 0.9*60=54mm/1000m?

[Mobius]

Question: If I have a penetration curve done by, say, US standards and want to convert it to, say, Soviet standard (providing I have one data point), is it as simple (for general impression) as simply using the same coefficient for all values, IE moving the entire curve up or down?

 

Example: I have US curve of say 100mm/100m; 80mm/500m; 60mm/1000m and a Soviet test giving say 90mm/100m, so can I then go with 0.9*80=72mm/500m and 0.9*60=54mm/1000m?

No. That doesn't quite work in practice. I may use a multiplier on one set but I have found the curves will not match. In practice with the right multiplier and all the data points i can make the curves cross somewhere 500-1500. One curve always seems to be steeper than the other. That is the best I can hope to get. Edited September 7, 2012 by Mobius

[alejandro_]

The full documentation on the famous Kubinka Tiger-II test has been uploaded. Its in Russian but pictures are very interesting.

 

http://litl-bro.livejournal.com/26198.html

[alejandro_]

Hey alejandro, I think I saw one of your old (2008) posts on ww2aircraft forum where you were posting discussion with someone called Soren.

 

Oh yes I am still waiting for the guy to send me a photo of an IS-2 obr 1944 with front glacis penetrated.

 

Did someone have Aberdeen data on the 88/L71 or was that just Rexford's WW2 Ballistics data?

 

You mean in that discussion? I think that data came from Aberdeen. It all seemed to be compiled and the 122mm data match that test you uploaded a while ago. Can you confirm?

[Mobius]

Did someone have Aberdeen data on the 88/L71 or was that just Rexford's WW2 Ballistics data?

 

You mean in that discussion? I think that data came from Aberdeen. It all seemed to be compiled and the 122mm data match that test you uploaded a while ago. Can you confirm?

It is a snippet copy of table from the WWII Ballistics book by Bird and Livingston. It is calculated data.

 

[Edit] Actually, I did some digging on 11 year old posts and found that is the Aberdeen data for the 122mm A-19 but adjusted for a velocity drop from 2634 f/s (803m/s) to 2600 f/s. But, the 122mm L43 had a muzzle velocity of 781m/s.

Edited September 11, 2012 by Mobius

[Marek Tucan]

Did some number crunching on the data that started this thread in comparison with others. It seems that the conditions for these tests were extremely harsh, as they seem to be 15-20% below both German tests and Soviet "Certified Penetration" tests. There are few exceptions, but usually the difference is this big.

[Marek Tucan]

Btw interesting thing regarding the 88mm L/71... While most of shells I've checked have conversion from 30°to 0° values (based on tests) over 1.2 (usually 1.2 - 1.25), in Spielberger the long 88 with PzGr.39/43 APCBC has only 1.08, suggesting pretty good performance vs. sloped armor. OTOH with undisclosed (but presumably older) projectiles from the Russian tests this is in the "1.2+" range.

[Mobius]

Btw interesting thing regarding the 88mm L/71... While most of shells I've checked have conversion from 30°to 0° values (based on tests) over 1.2 (usually 1.2 - 1.25), in Spielberger the long 88 with PzGr.39/43 APCBC has only 1.08, suggesting pretty good performance vs. sloped armor. OTOH with undisclosed (but presumably older) projectiles from the Russian tests this is in the "1.2+" range.

It appears that way. But on the US converted data the slope modifier is 1.138

We went over this before here.

http://208.84.116.223/forums/index.php?showtopic=18562&st=180

I'd side with the Yugoslav tests.

[bojan]

Mobius, I will say that both are relevant, just that target plate was quite different from what we we shoting at in '60s... Don't forget there was plenty of oddities in Yugo tests also, like 100mm performing way better then 88mm vs M47 glacis while in other tests 100mm and 88 had quite close performances etc.

Then note quite a difference in performance of 57mm ZiS-2 vs Sherman vs T-34 glacis, while 75/76/85mm guns performed ~ same.

Simple answer is that we don't know what a test plate was here and what a criteria was.

Regarding criteria there was a pic of Ferdinand armor testing with 122mm BR-471 stuck in front superstructure armor, with 1/3 of projectile past the armor. By Soviet criteria that was not a penetration., even if IRL such shot would at least kill some crew...

Edited September 14, 2012 by bojan

[Mobius]

Mobius, I will say that both are relevant, just that target plate was quite different from what we we shoting at in '60s... Don't forget there was plenty of oddities in Yugo tests also, like 100mm performing way better then 88mm vs M47 glacis while in other tests 100mm and 88 had quite close performances etc.

The Yugo tests (T-54 and M-47) are excellent examples of the 88mm performing better against vertical armor than the 100mm but not as well against sloped armor.

Plus the Aberdeen 88mm/L71 test supplied by Cary Erikson:

3 7/16" @ 55: Two complete penetrations. both projectiles fractured. Projectile fragments passing through plate. One partial penetration projectile fractured. 3334 mv on two penetrations. 3310 mv on 21/2 deep partial.

[Mobius]

This data I found several years ago goes along with the data on the first page.

It does fill in some blanks and lets us know this is for the A-19 122mm/L46 gun.

[Marek Tucan]

Hmm, thought that both BR-471 and 471B were APBC of same general ballistics and the difference was only in the penetrating part shape (blunt nose for 471B) but from this it seems it was significantly better streamlined and retained more penetration at range.

[bojan]

BR-471 was plan sharp nosed AP w/o ballistic cap.

BR-471B was blunt nosed AP with ballistic cap.

[Mobius]

Nope. For some reason the early AP ogive nosed rounds didn't even have a ballistic cap.

 

 

Edited September 14, 2012 by Mobius

[bojan]

Which is exactly what I wrote...

[Mobius]

Which is exactly what I wrote...

That's what I get for not quoting Tuccy. Your post slipped in between his and mine.

Nope to this v.

Hmm, thought that both BR-471 and 471B were APBC of same general ballistics and the difference was only in the penetrating part shape (blunt nose for 471B) but from this it seems it was significantly better streamlined and retained more penetration at range.

[Mobius]

Btw interesting thing regarding the 88mm L/71... While most of shells I've checked have conversion from 30°to 0° values (based on tests) over 1.2 (usually 1.2 - 1.25), in Spielberger the long 88 with PzGr.39/43 APCBC has only 1.08, suggesting pretty good performance vs. sloped armor. OTOH with undisclosed (but presumably older) projectiles from the Russian tests this is in the "1.2+" range.

Tuccy, I found this chart. It is part of an Allied debriefing of German ballistic scientists after the war. The lines are hard to read but it appears the 88mm/L71 doesn't penetrate as much at 30 degrees as the Spielberger/Jentz charts say.

The legend on the one for Russian guns says it was done 11/1946 and was 'traced'. Indicating that it was made from a German original.

Edited September 18, 2012 by Mobius

[Marek Tucan]

That's from the BIOS report, right?

 

I noticed also that the 128mm got there much more penetration with PzGr.43 than usually quoted... Though the report mentions that "manufacturer standars differed from Army standardas, but there was conversion for curves" or something for that effect.

 

This "lower" curve is whrere, some 190 mm at 100 m?

[Mobius]

That's from the BIOS report, right?

Oh, yeah. I thought at first it was US, but it is British.

He he, I noticed on the Soviet chart the 57mm is listed as \L13 instead of \L73, those European 7s looked like 1s.

 

The 128mm gun here has a muzzle velocity of 920m m/s. The one listed in Jentz book is 880m/s.

Edited September 18, 2012 by Mobius

[Marek Tucan]

The 920 mps would place it for L/61 gun (FlaK/field gun), still the penetration is significantly higher than in Jentz.

 

OTOH from the report itself it seemed more naval oriented, so mabye the difference between Navy and Army demands? (the report mentions that manufacturer and army tests were different). In such case probably more attention would be paid to burster but maybe with softer armor?

[Mobius]

The 920 mps would place it for L/61 gun (FlaK/field gun), still the penetration is significantly higher than in Jentz.

 

OTOH from the report itself it seemed more naval oriented, so mabye the difference between Navy and Army demands? (the report mentions that manufacturer and army tests were different). In such case probably more attention would be paid to burster but maybe with softer armor?

The Aberdeen data book has the 128mm Pak 44 Krupp Model w 920 m/s. Penetration 202mm/1000m/30° or (8"/1094/30°)

[Mobius]

What it looks like is the WWII Soviet ballistic model is a bit simple. Very linear. At least compared to the 1972 US and 1960 DDR model for the 122mm.

The shaded area is the DDR data for the 122mm/L43 gun. The impact velocity is taken from the US 122mm A19 table. The penetration of the A-19 is just from the corresponding velocity of the DDR table. .