Armor quality of Panzer III and IV

[critical mass]

When comparing ductile and brittle types of failure one need to factor in and guard against yet another important bias: Every material, even the most ductile types of armor can show brittle behavior in very cool ambient conditions. That is because the ability of the steel to exhibit plastic deformation is dependent on the ambient temperature, too. Armor steel has a temperature, where the change from ductile to brittle behavior takes place. F.e. most 1920´s US armor was having this temperature -measured by Charpy impact notch tests- at approx. 0°C with 1950´s US armor averaging at -50°C. Armor steel which has a very low brittle temperature is thus preferable. This is important when one tries to compare, f.e. a test made under summer conditions (say TIGER I trials) with another one executed at subzero temperatures (say famous TIGER II trials).

For those who are wondering, although the Tiger II was abandonned during some hot day in the summer, as far as I can remember - and correct me, if I'm wrong - the tests with the 122mm and 100mm guns were conducted during mid November 1944, when it was -2°C on average.

the recorded temperature of the trials was even lower (compare lower attachment).
The problems represents a unique bias for testing, though. That is because the engine isn´t running (steel is a good heat conductor).
Of course, the soviets didn´t pay that much attention to the issue in their own ballistic vehicle tests. Though we don´t know a lot about the ambient conditions in these cases, making direct comparison a very difficult project (like, f.e. IS2 with welded, RHA straight nose getting frontally penetrated by plugging by 88mm KWK43 at 450-600m through the glacis and at >4km through the nose plate, compare upper attachment).

[seppw]

This tank was taken out by a 75mm L46 in June 1944. Shermans are known to have used very mild and ductile steel, yet this looks like discing to me. It's easy to see how one can come up with the wrong conclusions about the ductility by simply looking the end result and without important additional information such as effect on the penetrator etc - and in this case even impact angle.

[Avalancheon]

The Kubinka report on the Tiger II is an interesting sample. If you had read tankarchives interpretation of the trials, you would be given the impression that the tank was a flaming piece of garbage. In fact, its armor held up very well in the strenuous conditions it was tested under. As critical mass pointed out, the ambient temperature at the test ground were -10 to -6 celcius. Thats cold enough to effect how the armor was behaving under impact. But even with that impediment, the Tiger II did not do poorly in the trials. Its armor actually displayed more ductility than the Tiger I.

tankarchives description of the Kubinka trials is full of exaggeration and hyperbole.

When the tank was shot at by the 122mm HE round, he tells his audience that it has been literally blown apart. And yet, he doesn't show a picture of how the Tigers armor reacted to the hit, even though they are provided in the report itself (!). When you look at the actual photographic documentation, then it becomes clear just how far removed from reality his description is.



In total, the 122mm gun in the test fired five shots against the glacis. There was the HE round, then four AP rounds. Two of them were the BR-471, and two of them were the newer BR-471B. Out of those four shots, only one of them actually pierced the armor. The ballistic capped BR-471B shell could penetrate at 600 meters, but not at 700 meters. So its range envelope against the Tiger II tank is limited.

This is literally the most powerful gun in the Soviet arsenal, firing the newest shells, and it can barely handle the tanks glacis! The armor didn't even fail in the brittle manner you would expect. Despite the cold, it was behaving in a ductile manner.

[critical mass]

Krogfuss deserves credit for pointing out that the range table ranges given in the Tiger2 firings are not based on accurate range table data.Revised, GDR range table for 122mm D25T tank gun firing 122mm BR-471B at V0=781m/s, official source, dated 1960, courtesey Mobius:

700m= 735m/s.
200m= 765m/s.

All firing was done at 100m distance. the velocity was controlled by using controlled filling charges and the velocity in front of the target recorded by selenoids. The specified distances of 500m were based upon faulty range table data and the A-19 field gun,-not the D25 tank gun.
The velocity given for 500m range table range was 771.1m/s (actually slightly more than 100m for D25T) and the velocity for 700m range table range with unscuccesful attempts was recorded with 759.3m/s (actually lightly less than 300m for the D25T).

[seppw]

The Kubinka report on the Tiger II is an interesting sample. If you had read tankarchives interpretation of the trials, you would be given the impression that the tank was a flaming piece of garbage. In fact, its armor held up very well in the strenuous conditions it was tested under. As critical mass pointed out, the ambient temperature at the test ground were -10 to -6 celcius. Thats cold enough to effect how the armor was behaving under impact. But even with that impediment, the Tiger II did not do poorly in the trials. Its armor actually displayed more ductility than the Tiger I.

tankarchives description of the Kubinka trials is full of exaggeration and hyperbole.

When the tank was shot at by the 122mm HE round, he tells his audience that it has been literally blown apart. And yet, he doesn't show a picture of how the Tigers armor reacted to the hit, even though they are provided in the report itself (!). When you look at the actual photographic documentation, then it becomes clear just how far removed from reality his description is.



In total, the 122mm gun in the test fired five shots against the glacis. There was the HE round, then four AP rounds. Two of them were the BR-471, and two of them were the newer BR-471B. Out of those four shots, only one of them actually pierced the armor. The ballistic capped BR-471B shell could penetrate at 600 meters, but not at 700 meters. So its range envelope against the Tiger II tank is limited.

This is literally the most powerful gun in the Soviet arsenal, firing the newest shells, and it can barely handle the tanks glacis! The armor didn't even fail in the brittle manner you would expect. Despite the cold, it was behaving in a ductile manner.

Shots #3 and #4 are pretty close to each other. For good measure, whenever homogenous armor is hit by a penetrator smaller than 120mm in diameter, the volume within two diameters around the hole can be significantly weakened, for bigger penetrators it's a little more. Without being able to measure it properly, I'd guess that shot #4 is just inside that area, but the shape doesn't look like it was affected too much. Perhaps because the plate's high thickness?
Nontheless, it would be interesting to know if a penetration had occurred further away from the previous hits.

[Avalancheon]

Krogfuss deserves credit for pointing out that the range table ranges given in the Tiger2 firings are not based on accurate range table data.Revised, GDR range table for 122mm D25T tank gun firing 122mm BR-471B at V0=781m/s, official source, dated 1960, courtesey Mobius:

700m= 735m/s.
200m= 765m/s.

All firing was done at 100m distance. the velocity was controlled by using controlled filling charges and the velocity in front of the target recorded by selenoids. The specified distances of 500m were based upon faulty range table data and the A-19 field gun,-not the D25 tank gun.
The velocity given for 500m range table range was 771.1m/s (actually slightly more than 100m for D25T) and the velocity for 700m range table range with unscuccesful attempts was recorded with 759.3m/s (actually lightly less than 300m for the D25T).

So because of these inaccurate range tables, the Soviets believed they were simulating a shot from 700 meters, when in fact, the velocity was actually more representative of a shot from even closer range? Interesting. That means the 122mm had an even smaller engagement envelope against the Tiger II.

One oddity with the Kubinka test is how the 88mm L71 failed to pierce the glacis, yet the 122mm L46 succeeded. (Albeit only with the BR-471B shells) Going by the 50% criterion, the 88mm actually has superior penetration against flat armor. Why would the 122mm have superior penetration against sloped armor? Maybe it has something to do with the T\D ratio...

Shots #3 and #4 are pretty close to each other. For good measure, whenever homogenous armor is hit by a penetrator smaller than 120mm in diameter, the volume within two diameters around the hole can be significantly weakened, for bigger penetrators it's a little more. Without being able to measure it properly, I'd guess that shot #4 is just inside that area, but the shape doesn't look like it was affected too much. Perhaps because the plate's high thickness?
Nontheless, it would be interesting to know if a penetration had occurred further away from the previous hits.

The shot spacing against the Tiger II was similar to the spacing used against the Tiger I. You think the Soviets would have used a larger spacing, given that much larger caliber weapons were being used!

And yet despite that abuse, the glacis shows no signs of brittleness at all. It resists four out of five hits, and when it does fail, it is in a ductile manner. Thats unquestionably a superior performance to the Tiger I.

[critical mass]

One oddity with the Kubinka test is how the 88mm L71 failed to pierce the glacis, yet the 122mm L46 succeeded. (Albeit only with the BR-471B shells) Going by the 50% criterion, the 88mm actually has superior penetration against flat armor. Why would the 122mm have superior penetration against sloped armor? Maybe it has something to do with the T\D ratio...

It´s not an oddity at all. At 50° impact, which is the minimum impact angle at close range for the TIGER Auf.B glacis, the 88mm Pzgr39/43 will not stay intact but regularely break up. I think this is why an angle of 50° and such a thick plating was choosen in the first place. The maximum a high quality, late ww2 Pzgr39 could be expected to stay intact is about 45°against 1.75 cal/plate, relatively soft RHA target plate (witness 75mm Pzgr39/42 in US trials vs US RHA), but likely less if the target plate was harder and/or the necessary striking velocity was elevated.
If the Pzgr39 breaks up, it will loose it´s advantage over larger calibre, deformable AP projectiles, such as the BR-471B because it will undergo a change of penetration mechanism and now needs to defeat by discing, rather than by ductile hole expansion or ductile plugging.

The 122mm breaks up at low and high obliquity alike, so it cannot be negatively affected by the high obliquity break up in the first place. This makes it appear like it has better angle performance than higher quality AP. But once one looks closer to the details, it´s performance is rather "capped" due to inferior projectile strength.

[Avalancheon]

It´s not an oddity at all. At 50° impact, which is the minimum impact angle at close range for the TIGER Auf.B glacis, the 88mm Pzgr39/43 will not stay intact but regularely break up. I think this is why an angle of 50° and such a thick plating was choosen in the first place. The maximum a high quality, late ww2 Pzgr39 could be expected to stay intact is about 45°against 1.75 cal/plate, relatively soft RHA target plate (witness 75mm Pzgr39/42 in US trials vs US RHA), but likely less if the target plate was harder and/or the necessary striking velocity was elevated.

Is this just a line of sight (LOS) complication for the shell? Or is there a certain angle that will automatically cause all APCBC shells to fail?

If the 88mm could handle a 154mm thick plate at 45 degrees, then could it handle a 109mm thick plate at 60 degrees? (I'm guessing the answer is a firm no)

If the Pzgr39 breaks up, it will loose it´s advantage over larger calibre, deformable AP projectiles, such as the BR-471B because it will undergo a change of penetration mechanism and now needs to defeat by discing, rather than by ductile hole expansion or ductile plugging.

The 122mm breaks up at low and high obliquity alike, so it cannot be negatively affected by the high obliquity break up in the first place. This makes it appear like it has better angle performance than higher quality AP. But once one looks closer to the details, it´s performance is rather "capped" due to inferior projectile strength.

So basically, the nose shattering is preventing the 122mm shells from bouncing off? If the plate was angled even more steeply, would this still happen?

What kindof shell design could the 88mm L71 gun have used to enable better performance against the glacis of a Tiger II? Something with a softer nose that prevents ricochet?

This tank was taken out by a 75mm L46 in June 1944. Shermans are known to have used very mild and ductile steel, yet this looks like discing to me. It's easy to see how one can come up with the wrong conclusions about the ductility by simply looking the end result and without important additional information such as effect on the penetrator etc - and in this case even impact angle.

I just saw your post now, seppw. There are even better examples I've seen of Sherman armor failing in a brittle manner from the cold weather. Take a look at his picture.

[Mobius]

Shots #3 and #4 are pretty close to each other. For good measure, whenever homogenous armor is hit by a penetrator smaller than 120mm in diameter, the volume within two diameters around the hole can be significantly weakened, for bigger penetrators it's a little more. Without being able to measure it properly, I'd guess that shot #4 is just inside that area, but the shape doesn't look like it was affected too much. Perhaps because the plate's high thickness?
Nontheless, it would be interesting to know if a penetration had occurred further away from the previous hits.

If you read one translation on shot #4 the shell stuck in the armor. Later an 80mm piece of armor fell off behind it. So you wonder how much help it had after it was extracted from its location.

[Peasant]

Mobius
Actually, the translation might be misleading. The original document doesnt say "The shell remained in the tank" but simply "shell in the tank" which I immagine means it was recovered afterwards from inside the tank.

Avalancheon
The hit #4 was made with the older sharp-tipped shell, btw.

There are even better examples I've seen of Sherman armor failing in a brittle manner from the cold weather. Take a look at his picture.

That's a T-34.

It's interesting to compare the performance of soviet shell vs KT armour with US testing of the same BR-471B in 1972:

We have 150mm/50° RHA of 255-269BHN. The shot #3 with a BR-471B managed to spall the rear face of the armour, I shall consider the lowest border of protection limit for this target as 771m/s (2528fps)

The US graph indicates the thickness defeated at 2530fps to be 4+5/8" or 117mm/50° of 241-277 BHN RHA. (US Protection Criteria)

The lower glacis 100mm/55° RHA of 255-269BHN. Again the same shell.
The shot #6 at 653m/s(2140fps) results in a cracked bulge. The actual P. limit is likely to be a bit higher than this.
US chart gives up 3+1/16" or 78mm/55° against 269-311 BHN RHA

I'll leave the chart here if anyone wants to check the numbers. https://imgur.com/5uOUxBm

[Mobius]

We have 150mm/50° RHA of 255-269BHN. The shot #3 with a BR-471B managed to spall the rear face of the armour, I shall consider the lowest border of protection limit for this target as 771m/s (2528fps)

The US graph indicates the thickness defeated at 2530fps to be 4+5/8" or 117mm/50° of 241-277 BHN RHA. (US Protection Criteria)

I don't understand where you are getting these numbers. Is it from the 1970s firing table or the incorrect 1944 firing table?

[Peasant]

I'm using the velocities specified in soviet test, since according to critical velocity its only the distances that are wrong, for KT tests and measuring with paint.net the BLs from the 1972 chart.

The captured KT plate's thickness/slope and hardness are specified in the original soviet document as the diameter of the Brinell test ball impression. I'm using this table to convert it in BHN: https://www.engineeringtoolbox.com/bhn- ... _1365.html

The chart specifies that it's calibrated against RHA made at MIL-S-12560 standard , of which I happen to have the specs laying around.

I wonder why the protection provided by KT armour was drastically inferior to what one might expect. One possible factor is that during almost 30 years that passed since WW2, the US RHA evolved to be much stronger per thickness basis. Either this particular sample of german armour was seriously flawed. I know they had difficulties in consistently producing good quality 80mm panther glacis plate, those probably would only be exacerbated with thicker plates.

[Mobius]

I'm using the velocities specified in soviet test, since according to critical velocity its only the distances that are wrong, for KT tests and measuring with paint.net the BLs from the 1972 chart.

I didn't see the velocities mentioned anywhere. Just the ranges. I wonder why hits #2, #3, #5, #6 and #7 didn't penetrate because they are the same kind.

[Peasant]

Doesn't look like our friend, Peter Samsonov, deemed important to translate those, but all shots with AP projectiles have the striking velocities recorded in the original documents.
Here, take a look yourself: https://mega.nz/#!XO5mAILR!kwFgFDmDdsHE ... eo-qfldKTw
Edit: it seems obvious that it penetrated only because it hit close to the previous shot.

[Mobius]

Well this is great. It has the 1944 incorrect firing tables

1944 Firing tables.jpg

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