rexford

Jeff Duquette posted some great photo's and info on the Yahoo!Tankers site regarding the T34 Model 1942 glacis and driver hatch, resulting in the following: 1. glacis measured from 50mm to 55mm thickness 2. driver hatch was much thicker than glacis, measurement from photo suggests total hatch thickness is about 44% greater than glacis (70mm hatch thickness for 50mm glacis, 65mm thick hatch for 45mm glacis) So, it appears that widely varying penetration ranges against T34 could be due to thickness variations. 75mm L43 hits on a 50mm thick T34 glacis would be resisted by 110mm vertical effective armor after high hardness decrease (0.79 multiplier), which would result in 7% penetration probability for 75L43 at 1250m. Add a few millimeters to the glacis armor, or a slight side angle, and T34 would be "safe" at 1235m as noted in George Forty's book. When Germans reproduced T34 armor plates for May 1942 firing tests, they used a thickness range of 42mm to 53mm, which seems consistent with the measurements Jeff Duquette took.

If the T34 driver hatch is 60mm thick, a 75mm APCBC hit on the center of the hatch would be resisted by an effective thickness of 144mm (quality of 1.00), which would defeat all 75mm L43 and 75mm L48 hits at any range.

A cross-sectional drawing on the following site (picture 2) suggests that the driver hatch was thicker than the 45mm glacis by about one-third, based on scaling; http://afvinteriors.hobbyvista.com/t34/t34a.html [ November 21, 2003, 05:37 PM: Message edited by: rexford ]

Several forums in the past have posted e-mails indicating that the subject tanks had 75mm thick driver hatches. Looking at a photo on the Russian Battlefield site at http://www.battlefield.ru/t34_76_2.html which is entitled "The new T-34-76 Model 1942 leaving the "Krasnoye Sormovo" Factory.", one can measure the approximate observed thickness of the gun barrel opening (76.2mm) and the open driver hatch edge thickness. Using a ruler and measuring against the photo, the driver hatch edge thickness appears to be 80% as thick as the gun barrel inner diameter (76.2mm) on the T34 Model 1942. Measured 5/50 of an inch across the barrel opening and 4/50 of an inch for the driver hatch thickness. The drawing at the top of the web site page results in about the same relationship. While the edge of the driver hatch appears to be about 61mm thick, it is possible that the 61mm edge might suddenly or gradually taper down to 45mm in the center areas (where the edge thickness was to beef up an area that is vulnerable to edge effects). Are there any design or production drawings out there that give a definitive driver hatch thickness? [ November 21, 2003, 05:45 PM: Message edited by: 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.

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.

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.

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 ]

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.

Originally posted by JasonC: "On the idea that the T-34s in the Kharkov area were something special or a quarter inch thicker, it is an absurd inference with absolutely nothing to back it." 5m is one-fifth of an inch (50mm vs 45mm), and it is not an absurd inference but a possible explanation, one of many possibilities. And it is not absurd, since the Germans modeled T34 armor with plates ranging from 42mm to 53mm thickness. Perhaps you just like to discount possibilities out of hand because they conflict with your ideas. "The obvious explanation is simply that 75L43 doesn't penetrate T-34s as far as some people thought." No, the obvious explanation is that T34 armor resistance seems to vary much more than other tanks, which is not unexpected given the stresses on Russian industry at the time. "The obvious place in Rexford's numbers is the 0.76 quality rating, which seems absurdly low on its face - there should be no surprise at all in .85 - if not higher still - being more accurate." Tell me why it seems absurdly low. What research have you seen for 45mm high hardness plates attacked by 75mm APCBC which suggests something higher is more plausible? "Yes that means lower kill ranges - the whole point of the thread is that the AARs from the actual participants are saying those would be correct." And the whole point of the thread is to show that there is conflicting into here, some suggests lower ranges and some suggests higher. "Instead of spinning that away, why not take it seriously? What is the supposed evidence for 0.75 - trials with somebody else's steel thought to be similar, instead of the real thing? Tests against entirely different guns at entirely different ranges?" U.S. ammo against U.S. high hardness armor results in about the same conclusions as German ammo against German reproduction of T34 armor. U.S. ammo against captured T34/85 armor shows that armor is much less resistant than medium hardness U.S. armor. "As for the 1600m figure, it doesn't say hull front so it is quite a stretch to pretend it must mean hull front." As I have stated so many times before, T34 were attacking German positions and front penetrations would be critical factor. "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." Your evidence is easily explained away, as usual. 75mm at 30 degrees resists 75mm APCBC like 92mm vertical, 75mmL48 penetration at 1500m is 97mm so given a slight side angle and random variations in projectile quality, 75mm L48 APCBC won't penetrate on every hit against 75mm/30 degrees. Regarding your comparison with T34 turret front, 1235m is stated "safe" range and most of T34 turret front is not a flat 70mm/30 degrees but highly sloped gun sponson areas, with a big flat mantlet in front. "If you look at CMBB numbers for L43 and L48 at 1500 vs. 30, they give 73.5 and 75 on a linear interpolation between 1000 and 2000. They will not fail against the SU-152 in CMBB because the latter is rated only 0.9 armor quality. German training documents and Russian range practices evidently did not recognize this supposedly low quality of the Russian armor." Why don't you package all of this with the proper references and bring it up with the designers. Some of what you say has merit and would make a very good case for change. "There is every indication the German 75mm numbers are somewhat generous (particularly for the L43, only 2mm below the L48 typically), and the Russian armor quality numbers low-balled when the AARs don't show it." The 75mm L43 fired APCBC at 740 m/s, the 75mm L48 at 750 m/s. That relates to an expected 1.9% difference in penetration. To say that a 2mm difference in penetration is "generous" shows that you didn't do enough homework to make a very good case. "Rexford speculates that German ammo "unevenness" may also be involved. Perhaps, but that is modeled by shot to shot variation." No it isn't if we are talking about a shipment of rounds from a specific maker that is appreciably below the average. "The tactical reality is the Germans did not treat the 75 as an "any range" T-34 killer but as a "km range T-34 killer" - and used it quite successfully that way, I might add." The above statement really says nothing, no one ever said that the 75mm L43 was an "any range" T34 killer. I offered to help you put together a package for submittal to the CMBB designers, complete with references and sources. Your response suggests that you wish to continue the same old arguments on this forum. [ November 20, 2003, 07:54 PM: Message edited by: rexford ]

If Kharkov 1943 T34 had 50mm glacis with 0.79 quality (calculated from our math model), the effective resistance would be 110mm vertical at 1.00 quality. With 101mm vertical penetration at 1250m, 75L43 APCBC would have a 7% penetration probability in the absence of a side angle. Assumes 5.7% standard deviation for German 75mm ammo quality variations. If 75L43 APCBC quality was less than average, penetration probability would decrease. So increasing T34 armor resistance by 19% over what was held to be the average (45mm at 0.76 quality) results in about the right range for 75L43 defeats in the one case under investigation. However, maybe the 1200m "penetration at any angle" and 1600m "max penetration" by 75L43 were against 42mm poor quality T34 plates using above average 75mm ammo. Who knows at this point which range is the true average? Maybe looking at German 50mm gun penetration cases against T34 will shed additional light regarding the real averages to be used for T34 armor. [ November 19, 2003, 07:26 PM: Message edited by: rexford ]

When the Germans duplicated T34 armor for early 1942 firing tests with 37mm and 50mm guns, they selected thicknesses from 42.1mm to 53.3mm with near constant hardnesses (around 450 Brinell or so). The above data suggests that T34 armor plates on hull could have ranged from just under 45mm to well over 45mm, which could account in part for the variable penetration ranges in the reports we have discussed. Regarding AAR's, a fellow on the Yahoo! Tankers site has a 1945 report from Hungary where Hetzer hits on the T34/85 glacis were failing at 250m range (if my memory serves me). Ammo quality variations could account for alot. Miles Krogfus has indicated that German 75mm APCBC nose hardness varied from 56 to 69 Rockwell C hardness, which could easily result in an ammo batch penetrating 10% less than average. On October 12, 2003, Miles posted the following on the Tankers site regarding German 75mm APCBC: "Sample lots from seven makers showed quality variations that would be equal to a circa 24 % velocity difference worst to best projectiles to perforate the same thickness of homogeneous armor plate. Four makers of U.S 75 and 76 mm M 61 and 62 projectiles showed a 20% velocity difference. Variation in quality of projectile made more of a difference when a projectile struck a plate than variations in armor plate quality." If the projectiles have the average halfway from best to worst and follow a bell-shaped curve, we're talking about the worst rounds penetrating -17% less than average and the best penetrating +17% more. A bad lot could penetrate 10% less than average for some unfortunate group of vehicles.

Ballistic data for effective resistance of sloped rolled plates against 75mm APCBC ammo results in following estimates for quality = 1.00 : T34 Glacis 45mm/60 degrees resists like 122.3mm vertical High hardness plate, highly variable quality W Sherman Glacis 63.5mm/47 degrees resists like 114.4mm verticalMedium hardness plate Hetzer Glacis 60mm/60 degrees resists like 174.9mm vertical Panther Glacis 82mm/55 degrees resists like 209.6mm vertical Variable resistance to cracking and (maybe) penetration Sherman Glacis 50.8mm/56 degrees resists like 119.1 vertical Tends to have quality below 1.00 due to inferior quality control, odd chemical compositions, poor heat treatment and multiple pieces which places welds in harms way

JasonC, The above notes contain some good stuff, which I would like to comment on a little so we both understand each other a bit better. A. Your point about 85mm AP being pretty poor against armor it should defeat is very good, and should be brought to the attention of the designers. If you want help packaging it I'am willing and available, we can do it on this forum or via private e-mails. B. Very good effort on 75L43 guns in GD use during early 1943, although a source would help. From the March 1943 report T34 knew they could stand off at 1235m and be "safe" against PzKpfw IV's. This suggests that armor resistance for T34's in Kharkov area was well above other T34's, it doesn't suggest that ALL T34 had same quality armor. Say penetration probability for 75L43 hit on T34 glacis at 1235m is 5%, this means resistance is about 112mm vertical. So, either the 45mm/60 degree plates have a quality multiplier of 0.92 or maybe the plate thickness is close to 50mm with a quality of 0.80. From you have presented it does appear that the T34 's at Kharkov in the spring of 1943 were much more resistant than the average T34 that is modeled in CMBB. C. Tell me what Jentz says on pages 36 and 37 in Vol. 2, I sold my copy long ago. Jentz also gives 1200m for 75L43 penetration of T34 at any angle, and 1600m max range. D. The 800m range for 75L48 against 47 degree glacis Shermans comes from where? The W series Shermans had 2.5" plates at 47 degrees slope, which resists 75mm APCBC hits like 114.4mm vertical effective according to our equations (quality is 1.00 due to improved quality control and heat treatment after 10/43). According to my calculations, 75L48 APCBC penetrates 114.4mm vertical at 807m without a side angle to the shot. So you see our calculations are in line with the reported range for 75L48 against 47 degree Sherman glacis armor. The Germans stated in a report that we obtained that 75L48 APCBC could not penetrate the 47 degree Sherman glacis at 1000m. One other thing, German quality of 75mm APCBC varied widely and so did nose hardness, so one might expect an average penetration range of 800m against 47 degree Sherman glacis armor with a low range of 600m on occasion. One or two AAR's do not a universe make, and one must consider ammo quality (as well as better than average armor). E. The U.S. analysis of T34/85 45mm plates (from Russian tanks found in Berlin ruins) showed that the armor ranged from poor to excellent quality, and firing tests showed that it resisted with less effectiveness than medium hardness U.S. armor. German firing tests against T34 like armor (same composition, high hardness and manufacture, with thicknesses in the 42mm to 52mm range) showed the armor to be inferior to medium hardness plate. My opinion on the March 1943 Kharkov T34 is that they had much more than 45mm thickness on the glacis, but this is speculation. Lorrin [ November 19, 2003, 05:32 PM: Message edited by: rexford ]

Placing six SU 85 vs 2 StuG IIIG during a December 1943 scenario on clear flat ground, 700m range, resulted in no clean 85mm penetrations that were not at weak points during the first turn. CMBB appears to correctly model 85mm APBC ammo, and does not do a reasonable job with 85mm AP against 80mm frontal armor, based on the two scenario's I tested. So, JasonC should bring this up with the CMBB design team but should be specific about the ammo types he is referring to. Whether it is due to overmodelling of two plates in contact, over zealous application of shatter gap or whatever is open to question. With regard to shatter gap, the basic theory is that an uncapped, low nose hardness round that strikes at 20 degrees to 45 degrees or so MAY fail to penetrate even though the penetration is 105% to 125% of the armor effective resistance. Hits at less than 20 degrees impact angle may not be vulnerable to shatter gap. It may be prudent and reasonable to ask how the shatter gap theory is applied in the game to 80mm armor hit by 85mm AP rounds at angles from 0 to 45 degrees.

Paul, The problem as I see with your equation predictions for the case where two face-hardened plates are in contact is just that, I doubt that the basis for your math is firing tests with face-hardened armor. As described in my earlier posts on this and other threads, homogeneous plates are weakest on the surface, since the armor in those areas is relatively unconstrained by surrounding material and is easiest to push out of the way. Two homogeneous plates in contact present twice the surface area of a single plate of the same total thickness, therefore two plates in contact are weaker than one plate. Face-hardened plates, on the other hand, obtain practically all of their resistance from the thin super hard surface layer, and two 30mm face-hardened plates in contact present two face-hardened layers with a total face-hardening that is more than twice as thick as one 60mm plate. Two face-hardened plates in contact should be better than one, while two homogeneous plates in contact should be less effective than one. With regard to air spaces, when a plate combination is hit and the round penetrates into the first plate, the bulge at the rear of the outer plate should reach back and touch the inner plate. So, from a ballistic perspective, two plates in contact with a tiny air space between them will be penetrated like two plates in contact without an air space between them. I do not buy the equation results since they appear to be based on a different armor type, and the air space theory does not seem reasonable once a round hits and penetrates into the outer plate. Lorrin [ November 18, 2003, 10:14 PM: Message edited by: rexford ]

I just set up a scenario, 7 T34/85 facing 5 StuG IIIG, June 1944, 85mm gun does not have any tungsten rounds. 650m range over flat unobstructed terrain. End of first turn, all five StuG III penetrated through frontal armor. No problem with 85mm APBC, which does not have an armor piercing cap and would be subject to shatter gap to some degree. Looking at the drawings of StuG IIIG, the driver visor that pokes out from the 30mm/50mm armor protection is probably one of the most vulnerable locations along with the 50mm flat slope mantlet on the gun. The upper superstructure on the StuG III consists of 30mm at 68 degrees from vertical and 50mm at 51 degrees. [ November 18, 2003, 10:41 PM: Message edited by: rexford ]

What is the basis for the calculations of face-hardened armor penetration as a function of projectile diameter and plate thickness? 30mm of face-hardened armor (FHA) plate resists like a 30mm FHA plate vs 37mm APCBC and 75mm APCBC, and the resistance at 10 degrees or 20 degrees from vertical would be slightly more than 30mm in both cases. The calculation that relates 30mm face-hardened plates to 23mm face-hardened resistance vs 76mm rounds is something I have never seen before. So far we have three bits of info on the resistance of two face-hardened plates in contact, one anecdote for 2 pdr and 37mm vs PzKpfw IIIH front hull, one U.S. firing trial for a variety of guns and ammo vs PzKpfw IV 30mm/50mm and the Cairo tests where different guns and ammo combinations resulted in about the same result. In no case did two FHA plates in contact resist like less than the total combined thickness. The photo's of PzKpfw IIIH front hulls that I have looked at over the years do not seem to suggest a 3" air space between plates, which would be more than twice the thickness of the 32mm add-on plate and one would think that it should show up in some picture. My guess is that the Germans would not allow a 32mm plate with a 30mm warp from straightness to pass inspection. Or even a 30mm plate with a 20mm warp. So what kind of airspace is needed?

JasonC, German reports from 1942 stated that the 75mm L43 penetrated T34's at 1200m regardless of angle, which probably included front and side shots. There were a large number of T34 knocked out, and it is unreasonable to assume there were no frontal hull hits. On paper, 75mm L43 APCBC should penetrate the side of a T34 well beyond 1600m on a flat-on hit, ditto for the turret front or mantlet on a 1942 T34. So I interpret 1600m max range as the most difficult to defeat frontal area with a limitation based on accuracy. Yes, CMBB does not give T34 armor the variability that appears to apply, and face-hardened plates in contact are very strong without too much for edge effects. Take it up with the game designer. Two face-hardened plates in contact provide more face-hardened layer distance than a single plate of the same thickness, and even if there is no air space between two plates I would expect the face-hardened resistance of 32mm/30mm to equal or exceed 62mm. Here's why there are misunderstandings regarding two plates in contact. Homogeneous plates in contact resist with less effectiveness than a single plate because the surface of those plates is less restrained by adjacent material and easier to push out of way. Two homogeneous plates in contact have more low resistance surface area than a single plate with same thickness. With face-hardened plates the resistance of the surfaces is greater than the interior, so two plates in contact should be more difficult to defeat. The British tests at Cairo (1942) show PzKpfw IIIH 32mm/30mm resists like 69mm, the U.S. firing tests against Pzkpfw IVG (30mm/50mm) suggest greater than 80mm resistance (with a possibility for less than 80mm), the British experience with 2 pdr and 37mm AP suggests 32mm/30mm resists like at least 62mm if not more. The March 1943 Tiger report indicates that T34 were "safe" at 1235m versus the panzers they were facing. When a T34 fires at a panzer and the panzer fires back at the tank that shot at it, the panzer gun will be aimed at the turret front of the T34 with no side angle. No side angle at all. 1235m safe range works for 50mm L60, does not seem 100% reasonable for 75L43. Lorrin [ November 16, 2003, 09:38 AM: Message edited by: rexford ]

thanks for the insights from the Russian side, many of which are new. When armor has an opening, it creates a weakness due to edge effects and added surface area. Striking near an edge or opening can significantly lower the effective resistance, so the Russian reports are consistent with ballistics. Good point. The hull machine gun port is going to be a weak point, in the initial combats between Panthers and M10's in Normandy the only M10 penetrations of the Panther glacis were through the machine gun ball mount and bouncers off the mantlet bottom that went through the hull top. Another good Russian point. Inconsistent powder charges made the U.S. 75mm M72 AP round an adventure in North Africa when Grants fired it against panzers. Thanks for sharing those notes with us. Anything on how far away from 75mm L43 guns a T34 would have to stay to feel safe?

JasonC, Yes and no. Why would a T34 M43 with 70mm slightly sloped turret front armor and a 52mm flat mantlet hanging out in front of the turret be safe from 75L43 APCBC hits at 1235m? A report in Jentz has 75L43 APCBC destroying attacking T34's at 1200m from any angle and 1600m max. Valera Potapov has seen a Russian firing test report where 75L43 APCBC consistently blew through the T34 glacis at 1000m with a 30 degree side angle. Another report in Jentz indicates 1000m or so is about it for 75L43 vs T34. My response to you is: A. the data suggests extreme variability in T34 front hull resistance, which could result from some factories using a reduced plate hardness (350 Brinell Hardness plates could be less vulnerable than 450 Brinell). B. the AAR for T34 against StuG III front could be penetrations of the front superstructure (30mm and 50mm plates at a high angle), which makes up a much bigger percentage of the frontal target aspect than the 80mm driver plate C. there is insufficient data to define a single effective resistance for T34 front hull D. the Russians manufactured (starting late 1943) improved BR-350B rounds, with 10% more penetration against face-hardened armor than the standard BR-350B, although in very limited numbers. The special BR-350B penetrated 83mm face-hardened at 500m, the regular round 76mm. There's the 500m penetration against 80mm face-hardened. A round with 76mm penetration would obtain some successes against 80mm plates, though less than 50% of the hits. E. most Russian 76.2mm AP rounds were capped, but it wasn't an armor piercing cap it was a windscreen to reduce air resistance. F. our predictions for 75L43 APCBC against T34 front hull are consistent with the majority of combat reports and Russian firing test trials, so at this point we are in the lead. [ November 15, 2003, 09:20 AM: Message edited by: rexford ]

Playing the CMBB game recently, I noticed the 45mm/53 degrees armor listing for the front lower hull on the subject tanks. This looks like a mistake. The British analysis of a T34 M42 resulted in 60 degrees for the glacis and front lower hull, data on the OnWar site has 60 degrees for T34 and T34/85 front lower hull. The only reference to 53 degrees for the front lower hull is on the Russian Battlefield site at the following address: http://www.battlefield.ru/t34_76_2.html Although the drawing on the site indicates that the lower front hull armor is at 53 degrees from vertical, measurements from the drawing reveal a 60 degree angle. Please also note that the same drawing shows the hull side superstructure thickness at 40mm (40 degrees) even though it is actually 45mm. The Russian Battlefield drawing angle on the upper hull rear is listed as 42 degrees from vertical, but it measures 49 degrees from vertical and other materials also suggest it is close to 50 degrees. In short, the listed angles on the Russian Battlefield T34 drawings look suspect and may not be correct. The angles in our book for T34 and T34/85 (60 degrees for glacis and front lower hull, and 50 degrees for upper hull rear) seem more reasonable. [ November 13, 2003, 01:36 PM: Message edited by: rexford ]

Pages 126 and 127 from Forty's GERMAN TANKS OF WORLD WAR TWO present an account of two Tigers taking on a pack of T34. which is taken from German Defense Tactics Against Russian Breakthroughs (U.S. Department of the Army pamphlet No. 20-233). The T34's used to stand outside villages in ambush, at 1350 yards range (1235m), and wait for the panzers to come out to play. At 1235m, the T34 were safe from the panzer guns ("hitherto safe distance") according to the write-up since the panzer guns were outranged. Kharkov area, Grossdeutschland Division. I've thought about the situation many times and the main opposition likely to be facing the Russians would be PzKpfw III with 50mm L60 guns or PzKpfw IV with 75mm L43. If 1235m is a safe range it suggests that the turret front is immune. At 1235m, the 50mm L60 gun firing APC would penetrate about 56mm vertical plate at about 300 Brinell Hardness, while the 75mm L43 APCBC would defeat around 101mm vertical. German firing tests with 50mm rounds against 40mm-55mm of high hardness T34 type armor suggest that the resistance might be boosted by 20% or so above 300 Brinell plate. This potential boost from high hardness armor could help explain why 50mm L60 hits at 1235m would bounce off the front of a T34 at 1235m. The thing that puzzles me is why the Grossdeutschland Division would not have quite a few PzKpfw IV with 75mm L43 during March 1943, and T34 would have grown quite accustomed to fighting PzKpfw III's in the area with all the limitations of their APC rounds. If the T34 were standing at 1235m due to ineffectiveness of the 75mm L43 gun on PzKpfw IV, this may have some significant meaning in terms of how effective the 45mm front hull plates were against 75mm APCBC (although we would still have to explain the turret front and mantlet safety against 75mm L43 hits). Lorrin

GERMAN TANKS OF WORLD WAR II, by George Forty, has an interesting passage on page 67 regarding the effective resistance of the PzKpfw IIIH front hull (32mm over 30mm, both face-hardened by many but not all accounts). "from late 1941 many PzKpfw IIIs had extra face-hardened plates fitted, for example, on to the frontal armor, which defeated the 2-pdr and 37mm except at very short ranges. British tank gunners were complaining that their AP shot just bounced off the enemy tanks." It is unfortunate that a reference is not given. Anyway, 2-pdr and 37mm uncapped AP have 100m face-hardened penetration of 62mm and 65mm (vertical target armor), which suggests that 32mm/30mm on PzKpfw IIIH upper front hull was at least as effective as a single 62mm face-hardened plate, if not more so. The British tests in Cairo during May 1942 suggested that 32mm/30mm resisted like a single 69mm face-hardened plate. The penetration resistance figures from Forty's passage and the Cairo tests suggest that two face-hardened plates in contact did not lose resistance compared to a single face-hardened plate of the same overall thickness. In addition, U.S. firing tests against the 30mm/50mm face-hardened plates in contact on the front hull of PzKpfw IV's suggested that the effective resistance was similar or slightly greater than a single 80mm thick face-hardened plate. If the PzKpfw IIIH had carried 32mm/30mm homogeneous plates in contact, the effective resistance against 2-pdr AP hits would have been about 73% of the overall thickness, or 45mm. The reduction in penetration range due to using face-hardened armor instead of homogeneous would be 700m down to about 100m. [ November 07, 2003, 10:48 PM: Message edited by: rexford ]

GERMAN TANKS OF WORLD WAR II, by George Forty, has an interesting passage on page 67 regarding the effective resistance of the PzKpfw IIIH front hull (32mm over 30mm, both face-hardened by many but not all accounts). "from late 1941 many PzKpfw IIIs had extra face-hardened plates fitted, for example, on to the frontal armor, which defeated the 2-pdr and 37mm except at very short ranges. British tank gunners were complaining that their AP shot just bounced off the enemy tanks." It is unfortunate that a reference is not given. Anyway, 2-pdr and 37mm uncapped AP have 100m face-hardened penetration of 62mm and 65mm (vertical target armor), which suggests that 32mm/30mm on PzKpfw IIIH upper front hull was at least as effective as a single 62mm face-hardened plate, if not more so. The British tests in Cairo during May 1942 suggested that 32mm/30mm resisted like a single 69mm face-hardened plate. The penetration resistance figures from Forty's passage and the Cairo tests suggest that two face-hardened plates in contact did not lose resistance compared to a single face-hardened plate of the same overall thickness. If the PzKpfw IIIH had carried 32mm/30mm homogeneous plates in contact, the effective resistance against 2-pdr AP hits would have been about 73% of the overall thickness, or 45mm. The reduction in penetration range due to using face-hardened armor instead of homogeneous would be 700m down to about 100m. It's also worth noting that the Cairo tests showed that 32mm/30mm face-hardened had the same resistance regardless of projectile diameter, so scaling factors (T/D ratio) did not come into play. [ November 07, 2003, 10:54 PM: Message edited by: rexford ]