rexford

There were a horde of PzKpfw IV firing on a bunch of T34, and it seemed that all the hits landed on the front lower hull. Not your everyday happening.

Yes. But three T34 were knocked out in one turn with 2100m penetrations of the lower front hull by PzKpfw IVG without tungsten. So it can and does happen. And shouldn't have happened.

I lined up five elite PzKpfw IVG's against seven conscript T34 M43 in a June 1942 scenario. Range between tank lines is 1600m, no tungsten ammo. Every 75L43 hit on the T34 front upper hull penetrated or gained a partial penetration. Considering that the 75L43 APCBC penetrates 46mm of 60 degree high hardness armor at 1600m, and the armor quality is 90% (so 75L43 penetrates 51mm at 60 degrees), one would expect few harmless bouncers at 1600m even with a slight angle. By the way, I still find the 45mm at 53 degree front lower hull armor on T34 to be very questionable. In a 2100m scenario, PzKpfw IVG hits on the T34 front lower hull penetrated in every case (May 1942 scenario, no tungsten ammo). All T34 drawings measure a 60 degree angle on the front lower hull, many sources say 60 degrees. Only a possibly mislabeled drawing on the Russian Battlefield web site has 53 degrees.

Just guessing, but it may be that the two plates in contact on PzKpfw IV and StuG III were fastened together better than PzKpfw IIIH, and thus were able to survive hits by larger rounds. When PzKpfw IIIH came out, the biggest British tank and anti-tank guns were usually the 2 pdr (2.38 pound 40mm shot) and the Stuart 37mm (1.92 pound shot). The 25 pdr fired a 20 pound 87.6mm shot, but most British hits on PzKpfw IIIH might be by 40mm and smaller ammo. PzKpfw IIIH came out about the same time as Barbarossa, so the Germans may not have considered hits by 76.2mm ammo (just under 14 pounds). By the time PzKpfw IV's and StuG III's with 30mm-over-50mm face-hardened arrived, hits by 75mm and 76.2mm rounds were expected to occur on a regular basis. So I'am guessing that the level of connection strength was improved. It is interesting ot note that the Germans went to 20mm homogeneous spaced infront of 50mm face-hardened on the front of PzKpfw IIIL, M and N, and used something similar on PzKpfw IVF. Desert war vets state that after a few hits the 20mm high hardness spaced plate would crack up, and they suggested that I look at pictures of spaced armor PzKpfw III's to see how many were missing either the turret or hull front spaced plate. Many were missing a 20mm plate. While Russian (122mm ammo) and British (75mm ammo) tests showed that the 20mm spaced plate set off the HE burster in rounds, leading to defeat of the fragments by the 50mm hull plate, spaced 20mm armor did not become a fixure on PzKpfw IV. Possible maintenance problem.

Your point is very well taken. The Germans found that placing two face-hardened plates next to each other, 32mm/30mm on PzKpfw IIIH, presented great resistance to 2 pdr and 37mm AP rounds. On the other hand they found that the combination was a maintenance nightmare, angled hits tended to shear off the bolts or crack the welds (depending upon how the two plates were connected: PzKpfw IIIH used bolts and armor upgrades on older tanks used welds). British firing tests found that the 32mm/30mm layered in contact armor on PzKpfw IIIH resisted 37mm thru 75mm hits with the same effectiveness, equal to one face-hardened plate of 69mm thickness. During the British firing tests with no side angle, guns pointed directly in line with hull facing, the plates held together well even after 6 pdr and 75mm hits. From what I've read it was angled hits that created the headaches. Would a 75mm round create more connnection (bolt or weld) damage than a 37mm hit at 30 degrees side angle on a hit that failed to penetrate? Depends. The British found that when uncapped rounds failed against the PzKpfw IIIH the ammo broke up, while defeated hits with capped rounds like 75mm APCBC caused quite a bit of damage to the inside plate. The Germans gave up on two plates in contact on the PzKpfw III series with the PzKpfw IIIJ model (late 1941), the two plates in contact was the only way they could get out alot of tanks with more than 30mm armor while getting into gear with 50mm front plate production (or so I've read). It is interesting that after all the problems with PzKpfw IIIH the Germans kept on using layered armor with PzKpfw IV and StuG III.

JasonC brought up a very good question on the George Forty thread, why do the published slope effects for German 75L43 APCBC look so much lower than what was found during U.S. firing trials with 75mm ammo. A very good question that took me awhile to figure out. CMBB presents penetration stats vs typical enemy armor, and Russian plate used two distinct hardness levels during 1943, very high hardness for 65mm and below, and medium hardness for above 65mm. When 75mm APCBC hits high hardness plate the plate will lose resistance relative to medium hardness plate. So here's the scoop for 75L43 APCBC penetration stats presented in CMBB (based on my examination of the numbers): The 0 degree penetration stats are against medium hardness plate, the 60 degree figures are against high hardness. 75L43 APCBC Penetration Data ============================================ 100m 128mm at 0 degrees in CMBB (medium hardness) 58mm at 60 degrees in CMBB (high hardness) 47mm at 60 degrees with slope effect from U.S. firing trials (medium hardness) So CMBB is saying 58mm of high hardness armor = 47mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 81% as resistant as medium hardness. ============================================ 500m 117mm at 0 degrees in CMBB (medium hardness) 55mm at 60 degrees in CMBB (high hardness) 44mm at 60 degrees with slope effects from U.S. firing trials (medium hardness) So CMBB is saying 55mm of high hardness armor = 44mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 80% as resistant as medium hardness. ============================================== 1000m 104mm at 0 degrees in CMBB (medium hardness) 51mm at 60 degrees in CMBB (high hardness) 40mm at 60 degrees with slope effects from U.S. firing trials (medium hardness) So CMBB is saying 51mm of high hardness armor = 40mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 78% as resistant as medium hardness. ================================================ 2000m 82mm at 0 degrees in CMBB (medium hardness) 43mm at 60 degrees in CMBB (high hardness) 33mm at 60 degrees with slope effects from U.S. firing trials (medium hardness) So CMBB is saying 43mm of high hardness armor = 33mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 77% as resistant as medium hardness. ================================================ Our calculations indicate that 45mm plate at 60 degrees should resist 75L43 APCBC with 76% of the resistance of medium hardness armor, so CMBB is in line with our equations.

Jason brought up a very good question, why do the published slope effects for German 75L43 APCBC look so much lower than what is found during U.S. firing trials with 75mm ammo. A very good question that took me awhile to figure out. CMBB presents penetration stats vs typical enemy armor, and Russian plate used two distinct hardness levels during 1943, very high hardness for 65mm and below, and medium hardness for above 65mm. When 75mm APCBC hits high hardness plate the plate will lose resistance relative to medium hardness plate. So here's the scoop for 75L43 APCBC penetration: The 0 degree penetration stats are against medium hardness plate, the 60 degree figures are against high hardness. ============================================ 100m 128mm at 0 degrees in CMBB (medium hardness) 58mm at 60 degrees in CMBB (high hardness) 47mm at 60 degrees with slope effect from U.S. firing trials (medium hardness) So CMBB is saying 58mm of high hardness armor = 47mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 81% as resistant as medium hardness. ============================================ 500m 117mm at 0 degrees in CMBB (medium hardness) 55mm at 60 degrees in CMBB (high hardness) 44mm at 60 degrees with slope effects from U.S. firing trials (medium hardness) So CMBB is saying 55mm of high hardness armor = 44mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 80% as resistant as medium hardness. ============================================== 1000m 104mm at 0 degrees in CMBB (medium hardness) 51mm at 60 degrees in CMBB (high hardness) 40mm at 60 degrees with slope effects from U.S. firing trials (medium hardness) So CMBB is saying 51mm of high hardness armor = 40mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 78% as resistant as medium hardness. ================================================ 2000m 82mm at 0 degrees in CMBB (medium hardness) 43mm at 60 degrees in CMBB (high hardness) 33mm at 60 degrees with slope effects from U.S. firing trials (medium hardness) So CMBB is saying 43mm of high hardness armor = 33mm of medium hardness when it's hit by 75mmL43, so the high hardness plate is 77% as resistant as medium hardness. ================================================ Our calculations indicate that 45mm plate at 60 degrees should resist 75L43 APCBC with 76% of the resistance of medium hardness armor, so CMBB is in line with our equations.

Regarding real world slope effects, our book provides actual firing test data to support our results: 75mm L40 APCBC (all hits at about 2000 fps) 2.22 slope effect against 40mm plate at 55 degrees 1.86 slope effect against 47mm plate at 50 degrees 1.73 slope effect against 51mm plate at 45 degrees Notice that the impacts are low velocity for a WW II tank gun, proving that the slope effects are not inflated by "hyper velocity" hits. U.S. Army TM9-1907 provides actual firing test data for various diameter APCBC rounds at angles from 0 to 75 degrees from vertical. Analysis of British and German APCBC shows that the TM9-1907 are applicable to those countries' APCBC and APC ammo. As a check, we analyzed British firing tests with German 75mm and 88mm APCBC ammo against armor plate at 45, 50 and 55 degrees slope, and the slope effect curves derived from American TM9-1907 data closely predicted German ammo performance. [ November 26, 2003, 05:39 PM: Message edited by: rexford ]

The calculations are probably based on penetration data for proof rounds succeeding on five straight hits, which underestimates performance with production ammo at 50% success. The ranges are probably also based on a method that did not take into account the loss of resistance when high hardness armor is hit by projectiles that are wider than the armor is thick. And finally, the calculations probably assume a 30 degree side angle from gun barrel to hull facing, so 75L70 Pzgr 39 is landing on the T34/85 glacis at 64 degrees obliquity. The Germans also tended to use one slope effect against all armor thicknesses, while the slope multiplier depends upon the plate thickness/projectile diameter ratio. A 300m penetration range for Panther against the T34/85 glacis plate does not seem very realistic. [ November 26, 2003, 05:30 PM: Message edited by: rexford ]

Originally posted by JasonC: "The whole thread started with a statement that the Russians were immune at 1350 yards until the Tigers showed up, and that they were surprised at that range because of it." The whole thread started with the statement that during March 1943 around Kharkov T34's were felt to be immune at 1325m against panzer guns, not on all fronts. My response was that the armor thickness and/or quality, and maybe the ammo quality, caused that penetration range impact. "Rexford, your slope effect figures are higher than anyone else's, unless restricted to very high velocity rounds. The 75L70 is not the 75L43. CMBBs slope effects for 60 degrees for the ordinary velocity German 75s are 2.04 to 2.11 at 1000m, 2.21 to 2.31 at point blank." My slope effects are based on analysis of actual firing test data, and are superior to anything else around. Notice how Jason neatly side steps my example where U.S. 75mm APCBC hits 45mm at 60 degrees, and the slope effect is 2.71 for a round striking at less than 2000 fps. Jason, as someone told me a long time ago, instead of looking at game figures get off you *** and look at the figures suggested by actual firing tests such as TM9-1907 for low and medium velocity rounds. "Your 107 flat figure is 3mm higher than CMBBs for the L43, and CMBBs are higher than anybody else's. 98mm and 102mm are commonly given for the better PAK 40 or 75L48." First of all, 75mm L46 Pak 40 rounds are fired at a much higher muzzle velocity than 75mm L48, and should penetrate about 8% more. 792 m/s muzzle velocity for 75mm Pak 40 Pzgr 39, 750 m/s for 75mm L48 Pzgr 39. Many published sources got that wrong. My figures are based on German equations for proof and production rounds which were derived from firing tests. You know the commonly quoted 30 degree penetration figures for German ammo (Chamberlain & Ellis, Panzertruppen Vol I and II, etc.), well those figures are for proof rounds that have to penetrate on five straight hits. So those figures have nothing to do with production rounds that succeed on half the hits. My figures are for production rounds with half a chance to penetrate. Forget about the CMBB slope effects and look at TM9-1907. I would also note that slope effect is not a function of impact velocity, it is a function of plate thickness compared to projectile diameter for AP and APCBC rounds. "In CMBB the chance of a Russian T-34/76 of the Kursk era penetrating a Tiger at any range or aspect is miniscule, as most have probably experienced. Somehow Lt. I.I. Burschick, hero of the Soviet Union, managed to get credited with 6 of them during the battle of Kursk, in a T-34." What about hits on the 62mm lower hull side armor, Jason? T34 76.2mm ammo penetrates that thickness beyond 500m. "Checking the slope effects I also notice the curiousity that the T-34s 76mm is quite the outlier. It has slope effect 1.62 vs. 60 degrees at point blank, 1.44 at 1000m - confused." Jason, you show no understanding of Russian flat nosed APBC ammo, which has superior slope effects due to an anti-ricochet characteristic of flat nose ammo. With regard to the various published penetration ranges for German and Russian guns during the Kursk battle, they are sometimes based on alot of calculations which may have used questionable data. One site on Kursk indicates that the Russians fired APDS discarding sabot rounds during 1943, which they clearly did not have. Practically all Russian penetration figures published during WW II were against face-hardened armor, and the Russians used those figures to predict penetration ranges against tanks with homogeneous armor such as Tiger. So they made lots of mistakes. Jason, you need to learn more of the penetration and armor resistance basics before you try to analyze everything under the sun. [ November 26, 2003, 05:21 PM: Message edited by: rexford ]

CMAK has Shermans firing 75mm uncapped solid AP rounds which really penetrate homogeneous armor like crazy, but are much less effective than APCBC against face-hardened plates. But Sherman 75mm ammo will switch from AP to APCBC as time goes on. CMBO only allowed Shermans 75mm APCBC and the penetration figures did not consider the large HE burster, which dropped the penetration by about 10%.

Andreas, Thanks for providing the following material: From Jentz: 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>

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>

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 ]

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.

Sir, I have looked at and given serious consideration to all of the points you brought up, but there are many factors brought up in my posts which you have still not accepted as valid alternative explanations. In a different thread you attacked my calculations again, well, I would note that you never provide any equations, math or background for your assertions which makes me think that you pull them out of the air. CMBB is not going to change their 0.9 quality for late war Russian armor because you supposedly came across a training document which provides a 1500m range where 75L43 penetrations against the SU 152 are less than reliable. Get real. Lorrin [ November 23, 2003, 06:08 PM: Message edited by: rexford ]

The following two quotes are by JasonC: "The 75L43 is simply overrated and Russian armor quality is underrated. The same gun is said to fail against SU-152 front hulls at 1500m in German training documents." "Other evidence that German 75s had middling ranges - in a book on StuGs I found a discussion fo tactics and ranges that mentions the danger from SU-152s, which included the point that they like to stand off at 1500m, because the German gun won't reliably kill them at that range while their reply will. The SU-152 has only 75mm at 30 degrees - akin to the T-34 turret front, which is 70mm curved." Do both of the above quotations refer to a German training document as the source of the 1500m stand-off range by SU 152's, or do each provide a different statement on the same issue? As I noted in my previous post, training documents are not very trustworthy after analyzing quite a few of them (American, German, British and Russian). The Americans predicted in their pre-D-Day training documents that the 76mm gun on M10's and Shermans could adequately deal with Panthers and Tigers at over 1000m range with standard APCBC ammo.

Originally posted by JasonC: "75L43 penetration range against the 70mm turret is not greater than 1600m. There is no reason to believe so. The 75L43 is simply overrated and Russian armor quality is underrated." You are so wrong. 70mm at 30 degrees from vertical resists 75mm APCBC like 85mm vertical, which the 75L43 APCBC production round penetrates on half the hits at 2000m. The 70mm turret front area on the T34 Model 43 is extremely small and is not a good measure of the turret front/mantlet resistance. Look at a picture or drawing of that tank and see what a small area the turret front is. "The same gun is said to fail against SU-152 front hulls at 1500m in German training documents." I thought you said that range came from Russian combat experience against 75L48 guns? The data in German training documents is often based on very bad calculations that bear little resemblance to reality, after review by quite a few people on the Yahoo! Tankers site. I would never take a figure from a training document as a tried and true combat range. ""Do not multiply causes needlessly" - William of Occam. Has nothing to do with any unwillingness to consider anything. The simplest explanation is by far the most likely one; that is all." Now that sounds ridiculous, and is an easy way to quickly dismiss my arguments. My arguments are kind of involved and require quite a bit of thinking and cross-indexing with other facts, so a simpler explanation like "the penetration range must be shorter" is the more likely one? Rubbish. Jeff Duquette measured a T34 Model 42 glacis and it was in the 50mm to 55mm range, just as I had put forth as a possibility. Variability in the T34 armor thickness helps to explain quite a bit of the penetration range variations we have been discussing. You have several good points and I was going to help you put them together so they would make the best appearance, but I don't know if we can work together.

One of the things Jeff Duquette showed in his Yahoo! Tankers post was that front hull armor thicknesses can be obtained in a non-destructive manner. He measured the T34 glacis thickness with the driver hatch open, some other fellows have measured the Panther glacis and lower front hull thicknesses via the exposed edges on the weld line where glacis and nose armor meet.

Seems about right. During our research years ago we came across an Allied report where the measured thickness of the SU 100 front lower hull plate was 60mm, not the 45mm design spec. U.S. analysis of 45mm plates on Berlin T34/85 showed wide quality range, excellent to poor. [ November 22, 2003, 07:07 AM: Message edited by: rexford ]

Russians could have been aware of great need to protect drivers.

Read where 50mm guns were aimed at T34 driver hatch, which could have been to dislodge or break hinges, or to take advantage of edge effect penetrations.

went back and remeasured the T34 hatch areas several times after a good night's sleep. top area of hatch that overlaps glacis is from 35% to 40% of glacis thickness.

JasonC said: "No magical half inch changes in armor thickness, recorded nowhere. No magical +/-30% variations in armor quality." First off, 53mm vs 45mm is an 8mm change. Secondly, a guy at a museum measures over 50mm for the T34 glacis, a measurement of an SU 100 lower hull front by the Allies is 60mm (!) while the design spec is 45mm, and the Germans use 42mm-53mm plates to duplicate the resistance of T34 hull armor during early 1942. U.S. analysis of T34/85 armor shows the 45mm plates to vary widely in quality, from excellent to poor. U.S. firing tests against 45mm plates from Berlin T34/85 show that high hardness plates are inferior to medium hardness armor when projectile diameter is greater than plate thickness, which is what our model shows (45mm high hardness plates lose 24% of resistance under 75mm APCBC attack). And still JasonC refuses to accept any views contrary to his own that explain the points he is trying to make. There seem to be reasonable explanations for the 1000m penetration range, and the 1600m penetration range. By the way, if 75L43 penetrates T34 glacis at 1000m and 30 degrees side angle it will just succeed at 1600m with no side angle (tank hull is facing directly at 75L43 gun barrel). If you accept 1000m penetration with 30 degree side angle you have to accept 1600m max range. Can't have one without the other. Also, if 1235m "safe" range against 75L43 is predicated on front hull hits and overlooks longer penetration range against turret front (as JasonC has stated), then 1600m max range is also probably based on same logic cause penetration range against turret front mantlet is much longer than 1600m. Consistent logic. Lorrin [ November 22, 2003, 07:23 AM: Message edited by: rexford ]

Research over the years on the penetration range of 75mm L43 APCBC against the T34 front resulted in the following bits of info: 1. T34 stands at 1235m and is "safe", outranging panzer guns, based on George Forty recounting of March 1943 report from Grossdeutschland Division experience. The 1235m "safe" range is consistent with figures presented in the next factoid. 2. 75mm Pak 40 cannot penetrate T34 beyond 1000m, German instructions to units on Eastern Front for Combating T34, May 1942. T34 76.2mm gun noted to be superior to 75mm L43, which would be the case if T34 has 50mm to 55mm glacis armor at 60 degrees slope and PzKpfw IV carries 50mm near-vertical frontal protection. "In correctly recognizing his technical superiority in weapons, the T34 already opens fire on German panzers at ranges from 1200 to 1800 meters." 3. 75mm L43 penetrates T34 at 1200m at any angle, with 1600m max range, spring 1942. Report included in T. Jentz' Panzertruppen Volume I. 4. 75mm L43 penetrates T34 front hull at 1000m with a 30 degree side angle during 1942 Russian firing tests, according to Valera Potapov notes from Russian report he reviewed. This result is consistent with 1600m maximum penetration range when gun is lined up with T34 hull direction. Whether the penetration range variations noted above are primarily due to changes in armor and projectile quality or T34 armor thickness are open to debate. Glacis thickness variations from 42mm to 53mm would certainly appear to support the above reports if all or most of the T34 in a group has similar armor thicknesses, which is possible if some factories aimed at greater thicknesses and others strove to meet the design spec as closely as possible.