Armor quality of the Tiger I

[Stiltzkin]

https://rostislavddd.livejournal.com/37 ... w=13102454

Ey, its Rotislav.

[Avalancheon]

Sorry everyone for resurrecting an old thread, but I have found important information relevant to this part here. A user on the russian speaking part of the Internet has posted scans of the very same report referenced in the book on his blog, which sparked quite a discussion in the comment section about the results obtained: https://rostislavddd.livejournal.com/37 ... w=13102454
Backup(scans only): https://imgur.com/a/q2BEXaD

I'm not gonna translate this because, even though I know russian, this writing is atrocious and the book pretty much sums it up with one but important exception: in the original it says not "12-13mm" but "12-13cm" which changes things completely. Since there are no thicknesses like these anywhere on the hull of the tank, we can only conclude that these shots were fired at the mantlet front which has thicknesses around 135-150mm in the central part.

Another mystery solved(?).

Good find, Peasant. Its nice to have this extra information.

This looks like an informal field test compared to the trials that were done in May 1943. (Which TankArchives describes in very fragmented fashion on his blog) The Soviets seemed to be putting their money on the 85mm gun as the solution to the Tigers armor.

[Peasant]

From what I gather, the 85mm was incapable of holing the 80mm/55deg glacis at any range and had difficulties to penetrate the 60mm/55deg nose plate at short range.

Normally this would be the case for a plate of RHA of good quality, but from what I seen between the ballistic test result of Panther tanks by soviets, british and americans this was hardly ever the case. With all the information I seen by this point the only logical conclusion to make is that late war mass produced german armour of 80+mm offered protection equivalent to about only 90% of its actual thickness.

Like I said previously, my first estimates about the effectiveness of soviet ammo were pretty pessimistic about the protection provided. Here are the revised numbers I'm currently working with as my go-to assessment of this gun.

[critical mass]

Peasant,

can u point out soviet ballistic trials in which they unambigiously defeated the Panther glacis with 85mm?

from what I have seen they failed to achieve this even from point blanc range.

thanks in advance,
cm

[Peasant]

Peasant,

can u point out soviet ballistic trials in which they unambigiously defeated the Panther glacis with 85mm?

from what I have seen they failed to achieve this even from point blanc range.

thanks in advance,
cm

Hi, cm.

Alas, I can not. I meant a defeat in the US Army/Protection sense, which is usually left out in the less detailed reports from the soviet side.

One soviet report indicates that 100mm BR-412 "defeats" Panther UFP at ranges of 1200-1400m.(striking velocity at 1300m 693m/s) I assume they are talking about complete penetrations here. From the British testing of BR-412B, interpolating between data points at 60°and 45° obliquity, give the limit thickness defeated at that velocity as 75mm/55° using US Army criteria.

To be completely defeated by the 100mm that particular Panther's glacis must've had equivalent thickness less than that, which makes possible a scenario where the 85mm gun could produce a US A/P defeat from extremely close range.

cheers, P.

[Mobius]

One soviet report indicates that 100mm BR-412 "defeats" Panther UFP at ranges of 1200-1400m.(striking velocity at 1300m 693m/s) I assume they are talking about complete penetrations here. From the British testing of BR-412B, interpolating between data points at 60°and 45° obliquity, give the limit thickness defeated at that velocity as 75mm/55° using US Army criteria.

From the US graph of Protection provided by cast homogenous armor to the 100mm Soviet BR-412B the 55° curve at 693m/s [2273 f/s] is 3.3" or 83.8mm. This is an estimated graph based on MV of 3400 f/s, but I'm not sure it matters to the impact velocity.

[Peasant]

From the US graph of Protection provided by cast homogenous armor to the 100mm Soviet BR-412B the 55° curve at 693m/s [2273 f/s] is 3.3" or 83.8mm. This is an estimated graph based on MV of 3400 f/s, but I'm not sure it matters to the impact velocity.

The m.v. shouldn't matter here. Something to re-iterate again because many people don't know this yet: as the obliquity increases the RHA advantage vs cast armour becomes bigger. At high obliquity the cast armour looses about 10-15% of its effective thickness. 84mm would be equivalent to 71 - 76mm of RHA.

The M-47 tanks UFP has effective thickness of only 85-90mm/60° RHA. This is why the guns like D-10T and Kwk 43 L/71 could penetrate it in the Yugo trials and couldn't that of T-54 and not because one is 210BHN and the other is 280BHN.

[Mobius]

The m.v. shouldn't matter here. Something to re-iterate again because many people don't know this yet: as the obliquity increases the RHA advantage vs cast armour becomes bigger. At high obliquity the cast armour looses about 10-15% of its effective thickness. 84mm would be equivalent to 71 - 76mm of RHA.

I haven't heard of that relationship before but for cast armor vs shell diameter 100mm of cast is 93% of the effectiveness of RHA vs 100mm shell size.

100mm br412b.jpg

[critical mass]

In regard to terminal velocity of the 100mm, the 1945 proving ground trials employed the following range velocity combinations:

100m = 888ms actual velocity
300m = 875ms actual velocity
500m = 855ms actual velocity
1000m = 829ms actual velocity

This suggests that the actual velocity tested for ‚1400m’ was considerably higher than 740m/s found in official range tables, which corresponds to a shorter range for the later corrected range table ranges than they believed initially.

Personally, I am very careful to attribute plate quality factors at high obliquely. Plate quality is not an invariable factor unchanged by obliquity. High quality plate at normal impact (fe soviet Medium hardness or HHA) will have very poor plate quality at high obliquely (acc. To soviet trials) while German RHA, which is of lower resistance at normal impact (the condition typically tested by the soviets) will show superior resistance at high obliquely (again, from soviet trials, using soviet and German ammunition).

US RHA is of further lower resistance at normal impact than German RHA, but again, at high obliquely, and in case it’s not an embrittlement affected plate, it can show very good performance, particularly if it also manages to break up the shot (due to softness of the US armor, breaking up high quality capped AP is more difficult for US armor than for British, German or soviet products).

Finally, the US chart gives the protection limit, which requires considerably thicker plate to prevent hole through formation than a penetration limit. At high obliquely, the delta between both can be considerably, depending on which way the plate gives in.

The reason RHA is superior at obliquely to cast armor is that the mechanical treatment by cross rolling strengthens the lateral and longitudinal strain limits. Cross rolling doesn’t improve through section strength, thus, at normal impact there is little difference to cast armor, while at oblique impact, the RHA plate can rely on the higher strain limits affecting a higher fraction of the total plate area.

[Peasant]

The m.v. shouldn't matter here. Something to re-iterate again because many people don't know this yet: as the obliquity increases the RHA advantage vs cast armour becomes bigger. At high obliquity the cast armour looses about 10-15% of its effective thickness. 84mm would be equivalent to 71 - 76mm of RHA.

I haven't heard of that relationship before but for cast armor vs shell diameter 100mm of cast is 93% of the effectiveness of RHA vs 100mm shell size.
100mm br412b.jpg

I believe I got this info from cm and he quoted the Lilienthal Report 166, and so far it explained very well the inconsistencies between the penetration values reported against RHA and the actual performance of these guns against real targets with cast armor.
Where did you get the 93% value from? I have a bad feeling it's from WW2BAG, am I correct? The authors have a bad tendency of extrapolating far reaching conclusions based on a small number of cases and their reported values often diverge drastically when compared with other examples than those used in the book.

Some of my musings on the difficulties of accurately estimating terminal ballistic performance of guns:
Large caliber shells loose velocity very slowly. Especially if they have windshields on them. The 122mm BR-471B looses about 6m/s between 2000 and 2100m or <1%(0,95% to be exact) of its velocity. To determine the distance at which this shell would defeat a given target with accuracy up to 100m would require to determine the ballistic limit with the same level of accuracy. Even the official values for BL, in most cases, have the Standard Error in order of 10's of m/s, which results in a Zone of Mixed Results for this shell extending at +-400m in either direction.

[critical mass]

Before I start my commentary on it, I suggest to familiarize with this article:

https://warspot.ru/16322-tolstaya-shku ... -zverintsa

Unfortunately, not the primary source but a selected range of excerpts and interpretations...

Notice the -unfortunatly unreferenced- ductile holding event of the 152mm AP impact on an RHA armor plate in the front cover photo. The impact is close to smaller ones (less than 3 cal distant), yet it shows fully ductile, plastic deformation. The armor gave in as good as could be wanted....

[Mobius]

In regard to terminal velocity of the 100mm, the 1945 proving ground trials employed the following range velocity combinations:
100m = 888ms actual velocity
300m = 875ms actual velocity
500m = 855ms actual velocity
1000m = 829ms actual velocity
This suggests that the actual velocity tested for ‚1400m’ was considerably higher than 740m/s found in official range tables, which corresponds to a shorter range for the later corrected range table ranges than they believed initially.

That is from the discredited 1944 flawed firing tables. (Incidentally it has 2400m = 763ms).
From the DDR table (source Miles)
Panzergranate mit Leuchtspur und ogivalem Kopf BP-412
200m = 864 ms
400m = 832 ms
1000m = 739 ms
1400m = 681 ms
2400m = 551 ms

Which is within 2 ms to the captured/translated Foreign Firing Table FT-F-50 pdf https://digitalcommons.unl.edu/cgi/view ... odmilintel

[Mobius]

Where did you get the 93% value from? I have a bad feeling it's from WW2BAG, am I correct? The authors have a bad tendency of extrapolating far reaching conclusions based on a small number of cases and their reported values often diverge drastically when compared with other examples than those used in the book.

Yes, WW2BAG. To disprove the table you would have to find vertical cast armor where firing results differ.

castvsRHA.jpg

[Peasant]

In regard to terminal velocity of the 100mm, the 1945 proving ground trials employed the following range velocity combinations:

100m = 888ms actual velocity
300m = 875ms actual velocity
500m = 855ms actual velocity
1000m = 829ms actual velocity

This suggests that the actual velocity tested for ‚1400m’ was considerably higher than 740m/s found in official range tables, which corresponds to a shorter range for the later corrected range table ranges than they believed initially.

The fact that this table has velocity at 0m as 900m/s leads me to believe that these are the terminal velocities for the 100mm HE shell. Comparing them with the official FT for OF-412 shell gives the following results:



I think you are jumping to conclusions here. Just because somebody once made a mistake of using wrong FTs, doesn't mean every single test made by the soviets has wrong striking velocities. It never hurts to be too careful, but in pretty much every other test they proved to know how to use firing tables to get the correct distances in.

Here is some soviet data that you might have not seen yet: https://imgur.com/a/hz3Uc8S

--many complicated words about how steel armor behaves at high obliquity--

Is it even possible to predict the interaction of shell and armour at high obliquity with so many variables affecting the results? Clearly there has to be some limits on what is possible, otherwise we would've seen photos of the UFP of KT penetrated by the soviet 45mm gun.
Is there really no lower limit on protection provided by the sloped armour (besides that it cant be less than its nominal thickness, obviously... right? at this point it wouldn't surprise me to learn that even this is not true.)

Before I start my commentary on it, I suggest to familiarize with this article:

https://warspot.ru/16322-tolstaya-shku ... -zverintsa

Unfortunately, not the primary source but a selected range of excerpts and interpretations...

Notice the -unfortunatly unreferenced- ductile holding event of the 152mm AP impact on an RHA armor plate in the front cover photo. The impact is close to smaller ones (less than 3 cal distant), yet it shows fully ductile, plastic deformation. The armor gave in as good as could be wanted....

Have you considered that the armour remained ductile because its structure was already compromised by a nearby hole, therefore it didnt offer as much resistance to the 152mm shell and did not absorb as much energy as an otherwise intact plate would've?

Yes, WW2BAG. To disprove the table you would have to find vertical cast armor where firing results differ.

castvsRHA.jpg

Not exactly. To disprove this (according to my own standards) one would need to find, at least, a dozen or so cases, which is not something I'm very keen on doing right now. I'm planning on using this document to do it, so meanwhile, if you want, you can take a look yourself.

[Mobius]

I think you are jumping to conclusions here. Just because somebody once made a mistake of using wrong FTs, doesn't mean every single test made by the soviets has wrong striking velocities. It never hurts to be too careful, but in pretty much every other test they proved to know how to use firing tables to get the correct distances in.

You are right. In firing tests even from the 1930s they are accurate. But in 1944 someone seems to have substituted HE ballistics for the AP ballistics in a number of cases.