George Forty on Panzers vs T34, March 1943

[rexford]

Originally posted by c3k:

Gents,

Regarding T-34 glacis resistance computations. It's all well and good to consider the slope, thickness, etc., but let's keep this in perspective. The glacis was the front of the tank. In the middle of the glacis was a big hole. The Soviets made 'em like that. It was the driver's hatch.

The glacis area near the edge of the hole will resist with a lesser ability than other glacis areas. This is the "edge effect" noted by Rexford. How far from the edge does the "edge effect" zone go? What is it's resistance? I assume some sort of gradation from near 99% theoretical maximum resistance to, as you approach the edge, a drop off to 0% resistance as you enter the edge. This _increases_ the area of weakness of the glacis.

The other zone of non-glacis resistance is, of course, the actual driver's hatch.

Thanks,

Ken

Good point.

Edge effects generally extend up to 3 projectile diameters from the opening, so 225mm or 9 inches, with varying decrease in resistance within distance.

Drivers hatch was 45mm thick and at same angle as glacis.

One would expect the max range for glacis penetration to possibly be based on hits near hatch edge (1600m). The 1200m at any angle penetrations would seem to be independent of hatch considerations.

Your point will take a while to look into. Thanks for bringing up something that slipped through the cracks.

[rexford]

JasonC,

How do you explain the Russian firing test result where 75mm L43 APCBC consistently penetrated the T34 glacis at 1000m with a 30 degree side angle? I metioned this in one of my recent posts on this thread.

The calculated resistance of the T34 glacis at 30 degrees side angle (compound angle is 64.34 degrees) is 107mm vertical using a 0.76 armor quality factor.

The 75mm L43 APCBC penetration at 1000m is 107mm, so the above test result supports the 0.76 armor quality factor for the ammo lot and T34 models that were fired upon.

Seems you overlooked the above situation in your last post.

Lorrin

[ November 20, 2003, 08:10 PM: Message edited by: rexford ]

[rexford]

JasonC stated that "As for in-game experiences, I have just had a SU-85 in June 44 (non Tungsten) fire three times at >80m frontally at a Stug. Three times partial penetration only. Is that shatter gap at work?"

Ran a scenario with 7 SU 85 lined up against 4 StuG IIIG at 850m during June 1944, no 85mm tungsten rounds.

Every 85mm APBC hit on the StuG IIIG penetrated the front hull.

No evidence of any shatter gap for 85mm APBC.

Regarding the impact of the driver hatch on T34 glacis resistance, there is some overlap where the hatch covers the edge of the glacis opening, which would decrease the impact of hits close to the edge since they would have to penetrate two 45mm plates in contact close to the edge.

The overlap may decrease the edge effect zone and percentage decrease.

Will look further into issue.

[rexford]

To respond to JasonC, the Tiger gave the Germans a gun which would consistently defeat the T34 glacis beyond 1000m.

While the 75L43 penetrated T34 glacis armor beyond 1000m in a number of cases, combat reports suggest that it did not defeat the armor in every case.

The above statements summarize what has been discussed on this thread.

[manchildstein (ii)]

Originally posted by rexford:

...My opinion on the March 1943 Kharkov T34 is that they had much more than 45mm thickness on the glacis, but this is speculation....

so there might have been one or more t-34 factories producing tanks with thicker armor; or do you think these might have been like "t-34 jumbos" with field-modified armor instead?

[flamingknives]

Originally posted by rexford:

JasonC stated that "As for in-game experiences, I have just had a SU-85 in June 44 (non Tungsten) fire three times at >80m frontally at a Stug. Three times partial penetration only. Is that shatter gap at work?"

Actually, that was Andreas.

[Andreas]

Originally posted by rexford:

JasonC stated that "As for in-game experiences, I have just had a SU-85 in June 44 (non Tungsten) fire three times at >80m frontally at a Stug. Three times partial penetration only. Is that shatter gap at work?"

Ran a scenario with 7 SU 85 lined up against 4 StuG IIIG at 850m during June 1944, no 85mm tungsten rounds.

Every 85mm APBC hit on the StuG IIIG penetrated the front hull.

No evidence of any shatter gap for 85mm APBC.

Hmm, I just tried this again (now to burn out his already knocked out Stug). The distance was actually 47m. I had three partial penetrations as I reported above. Now I had two 'shells broke up'.

The Stug is sitting at an angle to my SU85. About 45 degrees, about 50% of the shots hit the upper front hull and fail to penetrate, the other 50% go straight into the upper side hull.

[ November 21, 2003, 07:31 AM: Message edited by: Andreas ]

[rexford]

When an SU 85 fires on a StuG IIIG at a side angle of 45 degrees from hull facing, the front impact on the 10 degree slope driver plate lands at 49 degrees from armor perpendicular and the side hull hits land at 45 degrees.

The vertical equivalent resistance of the 80mm driver plate against 85mm APBC is 128mm, and the side armor puts up about 40mm vertical.

At ranges of 100m and over, all the hits in the above example bounce off the frontal armor and all side hits penetrate, although some of the frontal hits may partially penetrate into the armor without getting all the way through.

[Andreas]

Rexford

That is exactly the result I was getting, so I guess we can say that at least on this occasion Charles managed to take your advice

[Bastables]

Originally posted by JasonC:

If it is any consolation, Jentz does call them "75L43" IV longs. But there is no avoiding the inference, that at least in early 1943 both Germans and Russians thought the T-34 glacis was proof against a German long 75 at ranges over 1250m. See Jentz volume 2, pages 36 and 37 in the German edition (don't know if the pages are the same in English).

This is bull**** if the fig of 1250m is drawn from page 36 and 37 or any of the 1943 GD reports, as the GD report of 3rd April 1943 do not mention ranges of engagement of 7,5cm L/43. All it does mention is "sandwich" configuration of 8cm turret armour walls of the T-34. And that the Pzgr is ?exceptionally effective and "amazingly" accurate.

I would just like to reiterate; there is nothing to support the figure of 1250 metres in the GD reports. Most of the GD reports covered by Jentz deal with the new Tiger 13kp

The only report with ranges in Jentz vol 1 pertaining to early-mid 1943 is the 5th Pz div with PIV 7,5cm L/43, which notes lethal ranges of 1200m to 1600m: "every hit caused a destructive effect with the tank going up in flames." Pg36-38.

I go down with malaria, come back and you're still running around "mis-reading" sources in order to prove your point.

Jentz Vol 1 243

Pz regt 33

"4. Penetration Ability of the 7,5cm Kw.K 40 L.43 Pzgr 39 against the T-34 (31 July 1943)

The T34 is cleanly penetrated at every angle that it is hit at ranges up to 1200m."

The report also notes that the advent of the 5cm and 7,5cm lang has meant a definate superiority to the T34.

So you have one report giving the 1200metre range as the upper limit for a certain kill at "any" angle while another unit reports knocking out 1943 T-34s up to 1600meteres away presumably at low oblique angles.

[ November 22, 2003, 07:06 AM: Message edited by: Bastables ]

[Andreas]

The pages are certainly not the same in the English edition. Basty is quite right about his quote though, which is on page 41 of the English edition in a table analysing German gun/ammo performance.

It would be helpful if you could post the chapter number/heading instead of the page number Jason.

[JasonC]

"75mm at 30 degrees resists 75mm APCBC like 92mm vertical, 75mmL48 penetration at 1500m is 97mm"

Saysa you. I don't believe a word of it. They do not say "not every hit", they say "fails". I conclude that 75L48 at 1500m does not penetrate 97mm. It does not penetrate 92mm. I would not be at all surprised if your figures were fully 10% too high.

More, I question whether slope effect is entirely independent of armor hardness effects when the penetration is marginal. High hardness armor may shatter more easily on particularly flat hits, or on hits that overmatch the plate by a considerable margin, while resisting well on marginal penetration cases and vs. hits above some angle.

Every assumption in your conversions and formulas is a hundred times more doubtful than the eyewitness reports of actual tactical practice. If you did not need to multiple assumptions endlessly, the base prediction of the models would be a good guideline. But you require fudge factors of greater than 1.1 in actual armor thickness, of 1.3 in armor effect for the same angle and thickness, etc, then confidently pretend something like a 75mm penetration number at 1500m must be exact to less than 5%. You know no such thing.

And CMBB gets the SU-152 as wrong as the T-34. Because it accepts 90% quality ratings for Russian armor, it will KO that SU-152 practically every time. We know they did not actually do so. Just as we know the 75L43 regularly failed over 1250m, when with CMBB armor quality numbers it won't. We have tons of evidence that the 75mm penetration numbers are too high, and Russian armor qualities are too low.

If the tactical outcomes predicted by the modeling are wrong, then the modeling is wrong. And they are. So it is.

[JasonC]

Bastables - if you want to jump in please read the previous portions of the thread. Jentz shows that GD was using 75L43. See Rexford's very first post, that started the thread, for why that matters. The range comes from his own source. To save his expected ranges against T-34s, he had to assume his source was speaking of ranges for 50L60 guns. Jentz shows that GD on the date in question was using 75L43s, overwhelmingly, and moreover had been for some time. Therefore it is nonsense to ascribe the ranges in Rexford's own source to 50L60s. That is all I needed the citation of Jentz for - to demolish the possibility the 1250m range Rexford himself quoted referred to 50L60s.

[Andreas]

Originally posted by JasonC:

Just as we know the 75L43 regularly failed over 1250m, when with CMBB armor quality numbers it won't.

Jason

Could you please address page 41 in the English edition of Jentz please, where it explicitly states in a report from 5.PD, dated 20. March 1943:

7,5cm Kw.K. L/43 in 4 Pz.Kpfw.IV

[Knocked out] 17 KW-I, 26 T34, 1 T26, 1 Mark II, 3 Mark III, 1 General Lee

Pzgr.39 was fired at ranges from 1200 to 1600 meters. Every hit caused a destructive effect with the tank going up in flames. Two to three Pzgr.39 were expended per tank killed.

Somehow this does not jive with your statement.

BTW - anyone know which Mark II and III they refer to? Matildas?

[ November 22, 2003, 12:11 PM: Message edited by: Andreas ]

[Bastables]

Originally posted by JasonC:

Bastables - if you want to jump in please read the previous portions of the thread. Jentz shows that GD was using 75L43. See Rexford's very first post, that started the thread, for why that matters. The range comes from his own source. To save his expected ranges against T-34s, he had to assume his source was speaking of ranges for 50L60 guns. Jentz shows that GD on the date in question was using 75L43s, overwhelmingly, and moreover had been for some time. Therefore it is nonsense to ascribe the ranges in Rexford's own source to 50L60s. That is all I needed the citation of Jentz for - to demolish the possibility the 1250m range Rexford himself quoted referred to 50L60s.

Rexford?s reasoning is fine as the Forty Pz abt GD 13kp is describing the effect of rebuilt Pz regt GD (Feb 1943) advent with its PIV lang, StuG lang and Tigers deployed to Kharakov as part of Manstein counter stroke in an area previously held by PIII Lang heavy units = 4, 17, 18 Pz div and units that comprised 4th Panzer armee.

The only other units with PIV lang heavy regt were the other fresh units of II SS Pz corps attacking from the south.

Again none of the 1943 or 42 (Jentz) reports of 7,5cm L/43 pzgr 39 have 1200metres as the maximum penatration range. Max killing range seems to have been 1600metres.

The only place the 1200m upper limit seems to exist is in your own mind.

[ November 22, 2003, 05:14 PM: Message edited by: Bastables ]

[Panzer76]

Again, I would point out that BFC has admitted that, at least some, if not all, the penetration values in CMBB is wrong. Just compare the penetration value in CMAK and CMBB.

[Jeff Duquette]

Originally posted by Paul Lakowski:

</font><blockquote>quote:</font><hr />Originally posted by Jeff Duquette:

I’m not sure I get it. You are now saying the velocity component is not included in the spaced effect modifier?

So the spaced effect, or spaced modifier is not:

(t/d)^0.5 x 0.1d x V{in Km/s} x gap modifier

???

It should just be Spaced plate erosion by determine the t/d ; angle & effectiveness of the plate material .

Then (t/d)^0.5 to determine the 'spaced plate effect'

So 2cm Aluminum [0.5d] vs 3cm API becomes

2/3÷2^2=0.8 x 2= 1.6

1.6 x 0.5[te]= 0.8cm

The spaced plate effect becomes

0.8/3^0.5 = 0.5cm

If there is insufficent gap, multiply 'spaced plate effect'by x 0.7.

If the penetrator is high strength reduce the 'spaced plate effect' by x 0.7

So if the penetrator was high strength and the gap insufficent it should be x 0.5. </font>

[rexford]

Originally posted by JasonC:

"75mm at 30 degrees resists 75mm APCBC like 92mm vertical, 75mmL48 penetration at 1500m is 97mm"

"Saysa you. I don't believe a word of it. They do not say "not every hit", they say "fails"."

Give me the exact word they use, not your interpretation. Earlier you said the 75L43 would not reliably penetrate the SU 152 front at 1500m, which suggests it sometimes would.

Actually, it would sometimes penetrate the SU 152 front because the nose armor was 60mm at 30 degrees, so this brings your quotation above into serious question.

Looks like you are making stuff up as you go, so it would be good to give us the exact language.

"I conclude that 75L48 at 1500m does not penetrate 97mm. It does not penetrate 92mm. I would not be at all surprised if your figures were fully 10% too high."

Well, give us your figures and the basis for your estimates, which should be easy.

"More, I question whether slope effect is entirely independent of armor hardness effects when the penetration is marginal. High hardness armor may shatter more easily on particularly flat hits, or on hits that overmatch the plate by a considerable margin, while resisting well on marginal penetration cases and vs. hits above some angle."

Our research shows that our procedures work with all sorts of armor hardness.

"Every assumption in your conversions and formulas is a hundred times more doubtful than the eyewitness reports of actual tactical practice."

We got an exact match for 75L48 vs W Sherman armor. If you looked in our book you would see that we compared our penetration estimates to actual firing test data against captured tanks, and our figures came real close.

I would also note that a training document is not an eyewitness account.

"And CMBB gets the SU-152 as wrong as the T-34. Because it accepts 90% quality ratings for Russian armor, it will KO that SU-152 practically every time. We know they did not actually do so."

We know no such thing. A training document with an unreferenced penetration range statement is one of the worst things to base an argument on, and it is really worthless if it is just an estimated penetration range that was given to trainees.

"We have tons of evidence that the 75mm penetration numbers are too high, and Russian armor qualities are too low."

Provide some of it right here and right now. With references.

While we're at it, how about addressing the 50mm to 55mm glacis thickness on T34 Model 42, a possibility that you previously labeled as an absurd inference.

[Paul Lakowski]

Originally posted by Jeff Duquette:

</font><blockquote>quote:</font><hr />Originally posted by Paul Lakowski:

</font><blockquote>quote:</font><hr />Originally posted by Jeff Duquette:

I’m not sure I get it. You are now saying the velocity component is not included in the spaced effect modifier?

So the spaced effect, or spaced modifier is not:

(t/d)^0.5 x 0.1d x V{in Km/s} x gap modifier

???

It should just be Spaced plate erosion by determine the t/d ; angle & effectiveness of the plate material .

Then (t/d)^0.5 to determine the 'spaced plate effect'

So 2cm Aluminum [0.5d] vs 3cm API becomes

2/3÷2^2=0.8 x 2= 1.6

1.6 x 0.5[te]= 0.8cm

The spaced plate effect becomes

0.8/3^0.5 = 0.5cm

If there is insufficent gap, multiply 'spaced plate effect'by x 0.7.

If the penetrator is high strength reduce the 'spaced plate effect' by x 0.7

So if the penetrator was high strength and the gap insufficent it should be x 0.5. </font>

[JasonC]

Rexford asked "How do you explain the Russian firing test result where 75mm L43 APCBC consistently penetrated the T34 glacis at 1000m with a 30 degree side angle?"

The answer is that I do not trust theoretical slope effect multipliers too literally once they rise above 2 times, particularly against capped ammunition.

You say "The calculated resistance of the T34 glacis at 30 degrees side angle (compound angle is 64.34 degrees) is 107mm vertical using a 0.76 armor quality factor."

Since the actual armor is 45mm, 107mm implies 2.38 times for the slope and quality combined. I do not believe that can be resolved into 0.76 quality and 3.13 times for 64 degree slope. I have no reason to trust the 3.13x figure for 64 degree angle of incidence, with APCBC ammo.

APCBC tends to "grip" and rotate slightly on impact, reducing the angle actually presented to the round. The 60 degree slope of the armor is enough to ensure the round faces something like 2x (perhaps 2.2) the literal thickness. But I see no reason to place any confidence in a supposition that 64 degrees will always act like over 3x the actual thickness, and plenty not to.

I think the actual penetration of German 75mm APCBC at 1000m is around 100mm, not 107mm. I say so based on implied performance against many other AFVs and at other ranges. But I do not assume that Russian armor at 60 degrees from vertical and 64 degrees overall must be only .76 quality to act as only 2.2 times its literal thickness against APCBC. I consider that perfectly normal even for full armor quality.

Deductions from extreme angles are an unreliable way to infer armor quality levels. The actual multiplier experienced at a given extreme angle by a given round should be left to empirical determination. Calculated slope effects are fine for low angles, and reliable enough up to 45 degrees or so. I think the theoretical figures are fine vs. uncapped rounds up to 60 degrees or so. Beyond those limits (over 45 capped, over 60 uncapped, let alone both) you really want an empirical test of the exact plate and round involved, not a theoretical slope factor.

Rexford, I assume you have admitted (post Jentz citation) that GD was using Pz IV longs in the period discussed in your initial report, and that therefore the "hitherto safe distance" statement definitely refers to 75L43 vs. T-34 glacis, and has nothing to do with 50L60. This being the case, I refer you to your own initial statement in this thread, that if that statement was about 75 longs, it has drastic implications for actual penetration of the T-34 glacis.

I note, moreover, that no where does the report say or imply that there was anything special about the Kharkov area in this respect, or one particular batch of tanks faced. If it were, then there would be reports of new T-34s employing different tactics that had never worked against 75 longs before. Where are they?

Instead, the new aspect of the situation is not the protection of the T-34, it is the threat from Tigers. Those can now kill at ranges previously safe to the T-34. That the ranges mentioned as new Tiger kill territory are already 75mm kill territory in CMBB, argues that 75mm kill territory in CMBB is far too large to be consistent with this report.

[ November 24, 2003, 01:23 PM: Message edited by: JasonC ]

[rexford]

Jason,

All I have to say regarding your last post is that you tend to theorize without showing any references or math, and our research does not support your conclusions.

U.S. firing tests with APCBC show that at 60 degrees vs a 45mm plate, a 75mm round will be resisted by about 122mm vertical. A 2.71 slope effect.

Look it up in TM9-1907, and look it up in our book.

At 64 degrees vs a 45mm plate, 75mm APCBC will be resisted by about 150mm vertical, a 3.33 slope effect.

The Panther Fibel shows a 3.00 slope effect at 60 degrees for 75mm L70 APCBC rounds, and our analysis suggests the plate thickness was about 63mm or so.

U.S. firing tests vs high hardness armor at 60 degrees indicate that using our slope effects and high hardness modifiers results in close agreement with the trial results.

One of the interesting conclusions of our research is that at angles of 45 degrees and above, uncapped AP actually has lower slope effects than APCBC even though many books say the APCBC caps bite into the armor and retard the ricochet effect. Not at 60 degrees and many other angles.

Our figure of 107mm vertical at 1000m for 75L43 APCBC is based on analysis of German firing test results with the average production round.

I'am finished with your stuff until you start supporting your theories with numbers instead of conclusions. Nothing personal. Just can't do it.

Lorrin

[ November 24, 2003, 06:01 PM: Message edited by: rexford ]

[Andreas]

Originally posted by JasonC:

That the ranges mentioned as new Tiger kill territory are already 75mm kill territory in CMBB, argues that 75mm kill territory in CMBB is far too large to be consistent with this report.

What this report argues is that they are not.

7,5cm Kw.K. L/43 in 4 Pz.Kpfw.IV

[Knocked out] 17 KW-I, 26 T34, 1 T26, 1 Mark II, 3 Mark III, 1 General Lee

Pzgr.39 was fired at ranges from 1200 to 1600 meters. Every hit caused a destructive effect with the tank going up in flames. Two to three Pzgr.39 were expended per tank killed.

I note with interest you chose not to respond to it in any way. Is that because your bias is showing?

[rexford]

Originally posted by manchildstein II:

</font><blockquote>quote:</font><hr />Originally posted by rexford:

...My opinion on the March 1943 Kharkov T34 is that they had much more than 45mm thickness on the glacis, but this is speculation....

so there might have been one or more t-34 factories producing tanks with thicker armor; or do you think these might have been like "t-34 jumbos" with field-modified armor instead? </font>

[rexford]

Andreas,

Thanks for providing the following material:

Originally posted by Andreas:

</font><blockquote>quote:</font><hr />Originally posted by rexford:

C. Tell me what Jentz says on pages 36 and 37 in Vol. 2, I sold my copy long ago.

From Jentz:

1. In the period from 7 March to 20 March 1943, 250 T34, 16 T60 or T70 and 3 KW-1 tanks were knocked out.

2. The number of kills scored by each type of weapon were:

</font>

• 188 by Pz.Kpfw.IV 7,5cm lang</font>
• 41 by Sturmgeschuetz 7,5cm lang</font>
• 30 by Pz.Kpfw.VI (Tiger)</font>
• 4 by 7,5cm Pak (mot Zug)</font>
• 4 by 7,5cm Pak (Sfl)</font>
• 1 by a direct hit from a sIG</font>
• 1 using a Hafthohlladung</font>

(PR GD began with 5 Pz II, 20 Pz III 50L60, 10 Pz IV 75L24, 75 Pz IV 75L43, 9 Pz VI 88L56, 2 PzBefWg 50L42, and 26 Flammpanzer III. Their losses and total write offs amounted to 1 Pz III 50L60, 1 Pz IV 75L24, 11 Pz IV 75L43 and 1 Pz VI Tiger).

3. Degradation of the Russian armour steel was not noticeable. However, the armor steel is darker and finished rougher. The tanks reveal they were produced in a short time, because there is no evidence of any close tolerance work. The turret of the T34 is not made form a single piece,; instead it is assembled from numerous pieces. In many T34 tanks the armor walls wre created from pieces of 1cm thick steel with 6cm filling of cast iron or other material and then a second piece of 1cm thick steel.

I take it that is what you are after?

As for in-game experiences, I have just had a SU-85 in June 44 (non Tungsten) fire three times at >80m frontally at a Stug. Three times partial penetration only. Is that shatter gap at work?

Stug died nevertheless. </font>

[Paul Lakowski]

Originally posted by Andreas:

Originally posted by Andreas:

3. Degradation of the Russian armour steel was not noticeable. However, the armor steel is darker and finished rougher. The tanks reveal they were produced in a short time, because there is no evidence of any close tolerance work. The turret of the T34 is not made form a single piece,; instead it is assembled from numerous pieces. In many T34 tanks the armor walls wre created from pieces of 1cm thick steel with 6cm filling of cast iron or other material and then a second piece of 1cm thick steel.

What part of the T-34s armor is 8cm thick and what other materials do they use other than steel and cast?