Is the T-34's gun really under modeled in the game??

[ArgusEye]

Far be it from me to dismiss any test! It's just very unlikely that the 75mm (whether the 'French' or the later M3) would produce this effect. It is simply too large. It is a mediocre projectile, but it overmatches the first plate too much to just shatter outright. I'll believe it when I see the reports, but thus far I remain unconvinced.

Let me ask you this: Given that 50+30 was made quicker and cheaper, why would the Krauts switch to singular 80 if it resisted less?

Allow me to quote the september 24 1942 issue of Tactical and Technical Trends:

[...]

The 30-mm front armor of the original German Mark III tank (see this publication No. 3, page 12) is apparently a plate of machinable-quality silico manganese. The additional 30- or 32-mm plates which have been bolted onto the basic 30-mm armor are of the face-hardened type. This total thickness of 60 to 62 mm stops the British 2-pounder (40-mm) AP ammunition at all ranges, breaking it up so that it only dents the inner plate. The U.S. 37-mm projectile, however, with its armor-piercing cap, penetrates at 200 yards at 70°. Against the 6-pounder (57-mm) AP and the 75-mm SAP, this reinforced armor breaks up the projectile down to fairly short ranges, but the armor plate itself cracks and splits fairly easily, and the bolts securing it are ready to give way after one or two hits. If 75-mm capped shot is used, however, such as the U.S. M61 round, the armor can be pierced at 1,000 yards at 70°.

Similar results may be expected against the reinforced armor of the Mark IV.

The new Mark III tank has a single thickness of 50-mm armor on the front, and this was found to be of the face-hardened type. The 2-pounder AP projectile penetrates by shattering the hardened face, but the projectile itself breaks up in the process and the fragments make a hole of about 45 mm. The 37-mm projectile does not shatter during penetration, which is secured at ranges up to 500 yards at 70°. The 50-mm plate is softer than the reinforced 32-mm plates being 530 Brinell on the face and 375 on the back. This plate is not particularly brittle and there is very little flaking.

[...]

This shows only the uncapped (obsolete) 75mm round shattering. A cap on the thing, and the double plate loses all its advantages.

Finally: bear in mind that the double face advantage is most dominant in cases where the supporting armour is very thin, and 50+30 is quite a lot more meat than skin.

[undead reindeer cavalry]

sorry, i don't have enough time at the moment to really dig into this. IIRC the single plate approach was considered more economical.

going quickly by official numbers your quote's capped 75mm M61 round penetration equals about 71mm FHA. thus it would be crucial to know if they tested at longer ranges. if the combo plate would resists as 69mm FHA, the M61 should stop penetrating after around 1200 yards, again going only by official numbers.

EDIT: reminder for readers: the Soviet 76mm BR-350A is uncapped.

[undead reindeer cavalry]

oh my, i went to look at it again thinking about checking the 37mm numbers as well and i seem to really have mixed my curves earlier. i'm still going just with official numbers per August 1944 edition of "Terminal Ballistic Data" so it's far from proper analysis.

the capped 75mm M61 at 1000 yards at 20 degress equals around 78mm FHA penetration. 69mm FHA penetration would be at around 1500 yards.

200 yards at 20 degress for the capped 37mm equals around 61mm FHA penetration. to penetrate 69mm FHA it would require around 250 yards at 0 degrees or at 10 degress around 50 yards and "never" at 20 degress.

so if the 37mm numbers are correct and the Panzer III combo plate resists as 61mm FHA, like per 37mm penetrating at 200 meters at 20 degrees, the capped 75mm M61 should penetrate it at over 2000 yards. makes that 1000 yards number a bit peculiar.

i suspect the "TBD" curves for 37mm APC are either partly based on those trials without any thought given to the combo plate setup (it's quite a coincidence that the FHA penetration is exactly the combined plate thickness) or someone reported succes at 200 yards at 20 degrees simply by looking at the curves for 61mm FHA penetration (the wording in the quoted text is a bit vague which makes it possible if unlikely) or that they tested the 75mm M61 only up to 1000 yards (not realizing it would penetrate at double the range) or that here's simply too much at play for such simplistic curves to catch (naturally the most likely option).

the velocity difference alone is quite considerable for the two projectiles. the odd thing is that the 75mm should benefit both from the overmatch and lower velocity (considering the angle).

BTW i also checked 37mm APC for that single 50mm FHA plate and according to the same official curves it should penetrate it up to almost 800 yards. penetration at 500 yards at 20 degress equals 55mm FHA.

[ArgusEye]

Tricky business, isn't it?

These tests were done on enemy armour. This is available only in limited amounts. You need to capture tanks, and if they've burned they're unsuitable for these tests. And then, when shooting them up, you want to use as many different weapons as possible. On each plate type. At multiple angles. And especially when penetrations happen below plasticizing velocities (which only a few guns in WWII got close to), it is important to note that any hole or crack resulting from a previous shot makes the armour around it suspect, out to a radius of at least one caliber. This rather limits the amount of shots one can take at such a machine.

As such, I suspect the Brits never tried longer shots than 900 meters. This is already a distance that made a stationary tank hard to hit, given the British track record in gunnery accuracy. The round may very well be able to penetrate from up to 2000 meters, but they probably never tried it, because they had more relevant tests to expend the Kraut tank on.

One other thing I think you're noticing is that there is rather a spectacular difference between the different qualities of plate. To just convert armour thicknesses by giving them a percentage bonus or malus does not do the tricky impact physics justice. Not all German (or Soviet, or Pom, or Yank) armour is equal. Quite apart from the rapid deterioration in the last year of the war due to alloying problems, there were advances (and other changes) in the fabrication methods, which resisted one kind of penetrator more, and yielded more to another. The 10% difference from listed values for the 37mm is nothing astonishing in this light.

The 75mm SAP appears to have been designed with pre-war armour in mind, and was metallurgically dismally underdesigned. It was cheap, and against a 15mm front one only needs a bit of mass to just smash through. According to a report by the Italian RCA, it would shatter against the M11/39 front - even then, it would induce spalling. It is unfortunately not clear if this is incidental or structural.

Finally, bear in mind that TBD was constructed from multiple sources, so the relevant test might well have been done against British FHA, which was notoriously bad and therefore not used much.

[undead reindeer cavalry]

there is rather a spectacular difference between the different qualities of plate. To just convert armour thicknesses by giving them a percentage bonus or malus does not do the tricky impact physics justice.

certainly agree.

BTW i checked and didn't find any deeper insights regarding the two FH plate thing from Bird's and Livingstone's "book".

[ArgusEye]

Yes, opinions are easy to find, but facts are rare. At least the purported mechanism is clear now.

Furthermore, in the T&TT I quoted above, it says that the only face hardened plate was the bolted-on plate, with the one behind it being machinable. I assumed earlier that they didn't check the face hardening of the second plate, but I've come to understand that they actually did. This suggests that the second face hardening doesn't actually make the difference (because it isn't there). That makes the situation stranger. I'll try to dig into that.

[undead reindeer cavalry]

Furthermore, in the T&TT I quoted above, it says that the only face hardened plate was the bolted-on plate, with the one behind it being machinable. I assumed earlier that they didn't check the face hardening of the second plate, but I've come to understand that they actually did

certainly makes it all the more strange. i think it's the first time i have ever heard of a 30mm Panzer III front plate that wouldn't be FHA.

BTW i only now checked that T&TT article and see that they in fact do list longer ranges for other plate & gun combinations. some are peculiarly specific, such as 1700 and 1800 yards. PLUS they give general ranges such as "over 2000". in that context the 1000 yards figure for M61 seems to indicate that they think it wouldn't penetrate reliably at longer ranges (which would be extremely odd, considering they think the 37mm should penetrate at 200@20). i think it also means that at least some of those numbers are based on theoretical calculations.

it would be interesting to see the actual reports.

[ArgusEye]

Idle hope to see the originals - unless your sources are better than mine.

I've also been speculating what could have caused this odd measurement of the interior front plate. Has the tank burned, destroying the heat treatment? Was the machine always destined to have bolt-on armour, and therefore not hardened? Manufacturing error? Measurement error? Lies? Did they only measure the hardness of the inner face (because the outer plate was in the way)? Nothing is quite convincing.

As for the values you mention, they could have come from any number of tests or methods. Mathematical interpolation is a possibility (would be a shame though), but interviews with gun crews are another, as is finding random positions and only measuring the distance afterwards. It's unclear until we can find the test protocols.

[undead reindeer cavalry]

i think they are online but google is failing me. i only keep hitting 1944 tests. wrong terminology or something.

[ArgusEye]

Original result papers of 1944 experiments - online? That's fantastic, where's the link?

[undead reindeer cavalry]

lot's of separate parts here and there, mostly as scans. these two complete ones (but sadly offtopic) i bookmarked for later review:

http://wargaming.info/ww2-history/us-army-1944-firing-test-no1

http://wargaming.info/ww2-history/us-army-1944-firing-test-no3

[Bigduke6]

Here's a Red Army handout dated 1943.

Go here: http://www.rkka.ru/docs/real/sau/main.htm

The impression I get is, the Soviets felt 76mm could overcome 85mm German plate at 300m.

[ArgusEye]

Nice find! (and thank you!)

My Russian is *far* too bad to read this quickly, so could you tell me: are these the ranges that they expect one-hit penetrations, the ranges at which they expect to chew through the armour, or the ranges at which fire begins to have effect on the machine?

[ArgusEye]

Oh, and I forgot to say: I also think the 76mm could penetrate 80-ish armour at 300 meters. It squares with sources I found before, at least.

[dieseltaylor]

Great Stuff BD6

OK so what are the ATR's hoping for!!!

Great graphic representation. And presumably they did this for all Axis tanks?

URC

Nice to see figures on obscuration. A really big problem for hte better Allied guns. I do wonder if in game turns this does the Germans down a bit. Certainly Fireflies etc fire at vanilla SHerman rates despite the known lesse fire rate.

[ArgusEye]

URC, I apologise for not responding to your find earlier. What you have found is a report, but I'm not looking for that kind of report. You see, this is a transcript of a summary of results - which is a valuable source in and of itself. The problem with this report is that very much is left unsaid.

As so often, these reports are written by military men for military men, and it omits much of the information necessary for delimiting the applicability of the results. What I've been looking for, and it has been very hard to find, is sets of documents by the proctors and test designers, who explain the technical details of the test itself. That is quite rarely available.

Take, for example, the second link in your post. This is the famous Isigny tests. There are many references to original research papers, but all I've been able to find are quotes about them, and books containing them which are still classified. (This might tell you more about my searching skills than the availability though!)

In the Isigny tests, they got 4 or 5 Panthers together, and shot them up as described in the link you posted. It is unclear, however, what these Panthers had been through. They were made in a time that the Germans had trouble getting alloying materials, which made their temper extremely sensitive. If any of these things burned, their armour would have been severely compromised. The documents don't specify whether -and how much- this had happened.

There are plenty of opinions about the Isigny tests alone, which could be judged as to their factuality by just finding the complete documentation. Were the Panthers substandard? Had they burned? Was the 17pdr Sabot so inaccurate because it was just a bad batch of projectiles? Was the test biased in favour of the 76mm by its shot sequencing and target choice? All these points have been brought forward, but without more complete test documentation we cannot judge.

[JasonC]

Oh I can judge just fine, thank you very much. Shots went through a Panther glacis. But every imaginable spin must be put on that, because the metal was made in Germany. We understand completely. Too completely.

[ArgusEye]

Drama queening aside, have you no curiosity? Would you not rather know the fine details of what was tested? Are you not perplexed by the large differences in accuracy reported by the Isigny crew and the British for the 17pdr APDS?

[Joachim]

Well... first shot at the tanks from 4-800 yards. Several hits. "Failed" "not a fair hit" "old holes", "previous cracks"....

The likelihood of a shot hitting an old hole is rather low - if the glacis sports just 1 old hole. Not enough data to make up valid statistics, but conspicious.

Then finally at 2-300m the 76mm beats the glacis. Sometimes.

1 our of 4 hits on glacis #3 yields " 1. One rd penetrated glacis. After partially penetrating, rd turned and penetrated vertically. Photograph 24.". The best result.

2 other shots on glacis #2 yields " 1. One rd failed to penetrate. Depth of partial penetration 1 5/16". Photograph 21. 2. One rd penetrated through old hole; not a fair hit." So even the "best plate" never penetrated "fair" in the test had an old hole...

Conclusion: "Neither one can be be depended upon to penetrate the glacis plate of the Panther in one fair hit on average quality plate."

(Quotes from URC's link to Isigny test)

[jtcm2]

So what's the answer: is the 76mm undermodelled or not ?

For that matter, is 85 mm undermodelled or not /

Years ago, I was playing against Graves Registration (if anyone remembers him). A late 1944 battle in Hungarian plains (maybe near Debrecen-- does anyone know the scenario ?) I was playing Soviets. Long scouting and infantry swarming found a Panther and a Nimrod (for I was fighting against Hungarians) behind a wood). My infantry molotoved the Nimrod and were starting to bother the Panther. At this point, I rushed a plt of T34-85s down a road to go and fight the Panther. They closed in, the Panther was still behind its woods, and then-- we both had to stop the battle.

What would have happened ? In CMBB (and in real life), a plt of T34-85 rushing to a frontal fight with a Panther at decreasing range, perhaps 300-200 m (admittedly one trying to shake off 1 plt of Russian infantry trying to grenade it)-- who wins ?

[Redwolf]

So what's the answer: is the 76mm undermodelled or not ?

For that matter, is 85 mm undermodelled or not /

Years ago, I was playing against Graves Registration (if anyone remembers him).

Sure do. Good player.

A late 1944 battle in Hungarian plains (maybe near Debrecen-- does anyone know the scenario ?) I was playing Soviets. Long scouting and infantry swarming found a Panther and a Nimrod (for I was fighting against Hungarians) behind a wood). My infantry molotoved the Nimrod and were starting to bother the Panther. At this point, I rushed a plt of T34-85s down a road to go and fight the Panther. They closed in, the Panther was still behind its woods, and then-- we both had to stop the battle.

What would have happened ? In CMBB (and in real life), a plt of T34-85 rushing to a frontal fight with a Panther at decreasing range, perhaps 300-200 m (admittedly one trying to shake off 1 plt of Russian infantry trying to grenade it)-- who wins ?

BFC's "curved" rating on some plates makes this difficult to evaluate out but as long as the T34s are allowed to stop they should wax the Panther fine, both in real life and in the game. Of course a couple shell bounces and some good luck can reverse that quickly.

[ArgusEye]

So what's the answer: is the 76mm undermodelled or not ?

For that matter, is 85 mm undermodelled or not /

76mm seems well modeled to me, the 85mm is probably undermodeled before early 1944 and overmodeled thereafter. I am more verbose in earlier posts of this thread. Others disagree with me.

What would have happened ? In CMBB (and in real life), a plt of T34-85 rushing to a frontal fight with a Panther at decreasing range, perhaps 300-200 m (admittedly one trying to shake off 1 plt of Russian infantry trying to grenade it)-- who wins ?

In game I wouldn't know, but you can easily test it by trying. In real life, the Panther would get bludgeoned to death if attacked from its front, but could take some T34s with it if it was lucky. If it presented any appreciable side angle, it would be a barbecue in seconds. If it was faster on the trigger, it *might* kill 1 T34. Is my humble opinion.

[jtcm2]

Sorry to be obtuse, but should 76mm be able to puncture a Tiger's skin at *any range at all* ? I felt that to be part of the issue.

Thanks re Panther vs T 34/85. Alas, my faithful iMac, after 10 years, just decided and went funny (I kept in on an older version of OS X specifically to play CMBB)-- and I can't get the CD to appear on the desktop anymore.

[Redwolf]

Sorry to be obtuse, but should 76mm be able to puncture a Tiger's skin at *any range at all* ? I felt that to be part of the issue.

"Skin"? Skin what?

Are you aware that the Tiger like all tanks has thinner armour on the sides and the back?

[jtcm2]

Yes, Redwolf. But is there not a post somewhere in one of the 25 pages of the thread where someone (you ? BigDuke ? Undead Reindeer ?) writes that that the CMBB 76mm cannot harm the CMBB Tiger at any range from any angle (including point blank)-- and that this doesn't seem to correspond to reality-- therefore that something must be wrong with the tests. (Did I get this right ?)

On another note, I just went to an exhibition in Paris on music in the URSS. If you like socialist realism:

http://www.cite-musique.fr/minisites/1010_lenine/index.htm