rexford

The IS-2 development notes on the subject web site suggest that Panther armor decreased in quality during the Summer of 1944 (see following web page: [url=http://history.vif2.ru/is2_1.html):] "Further, after the first encounters between the JS-2 and German heavy tanks, it turned out that the sharp-nosed 122 mm APHE round - the BR-471 - could only penetrate the frontal armour of a Panther up to 600-700 metres. The less powerful frontal armour of a Tiger could be penetrated at distances up to 1200 metres. However, at such distances only very well trained and experienced gunners could score a hit. The vertical armour of a Tiger I, although thicker than that of a Panther, was more easily defeated by the sharp-nosed projectile of the JS-2 Main Gun, whilst it often ricocheted off the sloped armour of a Panther. Later, Soviet designers noticed the blunt-nosed projectiles worked fine against sloped armour. After several tests, designers revealed the effect of "normalisation" (Read more about "normalization" effect here). The powerful HE round, OF-471, when fired at German tanks, caused cracking and could even completely tear off the front armour plate at the seam weld. The first results of the IS-2 in combat (backed by the results of its tests at the Kubinka testing grounds in January of 1944) forced designers to look for new solutions to its problems. However, in the summer of 1944, the problem of the poor AP performance disappeared. The performance of the D-25T gun of the JS-2 against the German tanks improved dramatically. The reports from the front described cases where the BR-471 APHE round 122 mm projectile fired from 2500 metres ricocheted off the front armour of a Panther leaving huge holes and cracks in it." The Allies also noted poor performance of Panther glacis during the summer of 1944, two of three Panther glacis at Isigny crack after a few 17 pounder APCBC hits and American analysis of glacis metal shows brittle characteristics and low impact resistance. It would seem from the above that Panther glacis plate armor was fine until mid-1944, and then brittle or reduced effectiveness armor may have appeared on both the Eastern and European Fronts. British analysis of Tiger and Panther armor prior to 1944 states that it was good with an occasional bad plate. If the slope multipliers for Allied solid shot AP are applied to Panther glacis, the resistance equals about 168mm for 80mm at 55 degrees armor, which is penetrated by 122mm AP at 625m, close to Russian combat experience of 600 to 700 meters. Since the AP analysis does not assume any loss in armor resistance, it suggests good quality ductile armor resistance during the initial IS-2 vs Panther engagements where the 122mm gun was used, which may have included cold weather battles (Panther armor would have performed well despite cold, attesting to good quality). Blunt nose 122mm APBC would penetrate 80mm at 55 degrees beyond 1500m, which is slightly larger than what the Russians reported. Bottom line is the Eastern Front combat model for Panther might assume good quality armor till summer of 1944, and then assign reduced quality modifiers to a percentage of the Panther glacis armor. U.S. firing tests against the rest of the Panther armor (besides glacis), and Russian statements regarding Panther non-glacis armor, indicate good quality. The percentage of Panthers that would be impacted by armor changes is not known. [ 12-30-2001: Message edited by: rexford ]</p>

Thanks for really great responses. The U.S. did armor flaw testing with a supersonic gizmo that bounced a wave and then tested to see if the wave was distorted by bad things in the armor. From the reflection they could also estimate the size of the flaw. I don't think the device would fit in one's pocket or airport luggage. The U.S. measured the plates on three Tigers and found that the actual thicknesses exceeded the design spec: 80mm plates were 81.5mm on average 60mm plates were 62.3mm 100mm plates were 103.7mm The Americans measured the 60mm nose armor on a Panther and it was 67mm. The 45mm plates on an SU 100 nose actually measured from 42mm to 60mm thickness. It would have been good if the actual thickness of the tank armor had been measured as it was taken apart and put back together. About the resistance of two plates in contact, there is very little on the subject and trying to make an equation from three tests is really stretching it. The equation predicts that when 15mm is put on top of 45mm the combination resists like a single 46mm plate: that top 15mm only adds 1mm to the effective resistance? To make the equation work requires alot of fudge factors, like making 15mm on top of 45mm resist like maybe 50mm (top plate adds at least 0.33 of thickness). I could see where a game designer might be suspicious of using an equation that has to deal with situations outside the data base where one applies "made up" multipliers. CMBO played it conservative, two plates together act like one plate with same overall thickness. The war was not won or lost based on whether the Sherman Jumbo resisted with 100% of total thickness or 96%, although it might impact a few scenario's.

If a round penetrated the superstructure side of a T34 (45mm armor at 40°), was there any sort of plate or shield behind the armor to further slow or help defeat the penetrating round? Years ago in the cloudy recesses of memory, I remember seeing a schematic of a T34 with a slice of the side armor removed, and it looked like there was some sort of vertical shield that penetrations of the superstructure would have to go through to reach the tank interior. The reason for this question is that 50mm penetration of the T34 side hull seems vey likely yet the hits often do little or nothing. If the hard side armor fractured the round then it might take very little behind the armor to neutralize the hits. So, if hits penetrated the 45mm at 40 degrees armor was it clear sailing? Thank you.

Paul Lakowski recently provided this writer with a copy of A. Hurlich's paper on SPACED ARMOR, which was published on November 20, 1950 by Watertown Arsenal in the U.S. The paper starts with a discussion of two plates in contact and presents data from a test at 45 degrees impact, where two 1.5" homogeneous armor plates were equivalent to a single plate with 2.3" thickness. The inferiority of two 1.5" plates to a single 3" plate was related to the ease with which material on or near the surface of plates can be moved. Two 1.5" plates in contact have considerably more surface area than a single 3" plate, leading to less penetration resistance. If the test results from the Hurlich paper are combined with two results from U.S. Navy tests, a broader view of what occurs when two layered plates are attacked might be obtained: 1.5" over 1.5" resists like 76.0% of combined thickness 3.0" over 1.0" resists like 92.5% of combined thickness 1.0" over 3.0" resists like 87.5% of combined thickness The above data suggests that thicker plates result in the retention of a high percentage of the combined thickness as effective armor (greater ratio of middle area to surface material), and placing a thinner plate in back of the thicker armor increases the resistance. The following equation reproduces the above results (where effectiveness is multiplier on combined thickness that resists penetration when two plates are in contact): Effectiveness = 0.3128 x (plate ratio)^0.02527 x (maximum thickness)^0.2439 where, "plate ratio" is thickness of first plate to be hit divided by underlying thickness "maximum thickness" is thickness in millimeters of thickest plate When two 100mm plates are in contact, the above equation predicts an effectiveness of .96, suggesting that two 100mm plates would resist like a single 192mm thickness. Effectiveness over 1.00 is not possible, and a limit on how large the factor can be probably exists. Due to the limited data base the equation is preliminary, and additional test data and suggestions would be appreciated. ----------------------------------------- Sherman tanks carried applique armor on the hull side, adding 25mm on early versions and 38mm on later models to protect the ammo racks. Using the above equation, 25mm/38mm on early Sherman hull sides would resist penetration like 0.75 x 63mm, or 47mm, and 38mm/38mm would be equivalent to a single plate thickness of 58mm. The 89mm+89mm Sherman Jumbo cast mantlet would resist like a single casting of 166mm thickness, which would be the same as 166mm of rolled armor. The Sherman Jumbo glacis, 38mm over 63.5mm, would resist like a single rolled plate with 86mm thickness. The resistance against 75mm and 88mm APCBC, corrected for slope effect, would be about 172mm and 163mm of vertical rolled plate. Panther and Tiger II hits on the Sherman mantlet and glacis might be expected to penetrate at: Panther penetrate mantlet at 550m penetrate glacis at 400m Tiger II penetrate mantlet at 2100m penetrate glacis at 2600m Since the math model is preliminary, it would be interesting to see if any combat reports confirm or contradict the above estimates.

Recently surfaced data strongly suggests that solid shot AP without an armor piercing cap has significantly lower slope effects than APCBC-HE at angles from 45 through 65 degrees. This result is rather surprising since common wisdom is that sharpy pointed AP outpenetrates APCBC at small angles but is inferior at steep slopes since the sharp nose is a handicap (tends to bend, which absorbs energy and decrease sloped penetration). Review of newly found data for 6 pdr, 17 pdr, 90mm T33 and 90mm M77 solid AP without armor piercing caps results in similar slope effects at similar T/D ratio's. Following compares solid AP slope effects vs APCBC-HE at similar T/D ratio: 55 degree impact, T/D=1.00 Solid AP, 2.17 APCBC-HE, 2.55 45 degree impact, T/D=1.00 Solid AP, 1.79 APCBC-HE, 1.82 65 degree impact, T/D=1.00 Solid AP, 2.91 APCBC-HE, 4.00 The British report on German 75mm and 88mm Ammunition at Oblique Angle states that solid projectiles should have superior slope effects, since the absence of an HE burster cavity increases the bending resistance. For angles from 45 to 60 degree, the following equation describes the slope effect multipliers for solid AP without armor piercing cap (^ indicates that previous term is raised to following factor): slope effect = A x (T/D)^B, where A = 0.7152 x 1.02047^(angle) B = 0.07791 x 1.00949^(angle) At 65 degrees impact, the slope effect equation is: 2.908 x (T/D)^0.1864 When 90mm M77 or T33 strikes the Panther glacis at 55 degrees impact, the slope multiplier will be 2.15 and the effective vertical resistance will be 172mm at 0 degrees. When 90mm M82 APCBC-HE hits 80mm armor at 55 degrees the vertical resistance is about 200mm at 0 degrees.

Based on penetration data for U.S. 90mm AP shot available during WW II, M77 AP and T33 APBC, penetration of the Panther glacis should have been a regular occurrence at short and medium range. At ranges of 1250 yards and less, 90mm T33 APBC penetrates 3.15" (80mm) at 55 degrees impact (source is TM9-1907). 90mm M77 AP penetrates the Panther glacis at about 400 yards. Both ranges assume Panther hull is facing gun and ground is level. Despite the apparent ability of 90mm solid shot to defeat the Panther glacis at many combat ranges, the U.S. reports on 90mm gun effectiveness usually sound disappointing. This raises the possibility of other factors turning a round that should be effective into something much less. Research into the issue has turned up many references that point to a shatter tendency on the part of solid shot 90mm rounds. SPACED ARMOR, by A. Hurlich (WAL 710/930-1, November 1950), points out that when 57mm M70 and 90mm T33 solid AP was fired at a 1/2" plate at 30 to 60 degrees, 26 of the 57mm rounds went through the armor without shatter but 26 of 28 90mm AP shattered against armor that presented insignificant resistance. The 90mm shatter was attributed by Mr. Hurlich to longitudinal wave phenomena particular to 90mm AP, since the 57mm round was relatively long and thin and should have shattered before 90mm AP. The page from spaced armor that discusses 90mm T33 AP shatter against a thin plate has been loaded into the Files section at Yahoo! Tankers. Further evidence is provided in the penetration data for 90mm T33 and M77 solid shot. TM9-1907 shows T33 shot shattering against armor at 30 degrees that should be easily penetrated (penetrates 4.85" on half the hits at 2800 fps but should do about 6.5"), and the penetration range curves in THE VULNERABILITY OF ARMORED VEHICLES TO BALLISTIC ATTACK show M77 with a 1.80 slope effect at 30 degrees impact (about 1.25 to 1.30 is expected). During the December 1944 tests against two Panthers (subject of recent discussion about picture submitted by Packfanone on Yahoo! Tankers site), 90mm M77 AP lodges in the Panther glacis at 50 degree impact even through complete penetration probability is almost 99% probability, and only one of two hits against 55 degree glacis armor penetrate despite a very high success probability per hit. It would seem that something other than penetration-vs-armor resistance ratio's significantly impacted U.S. 90mm solid shot, and seriously detracted from the projectile effectiveness. 90mm T33 APBC is the same as M77 AP except for a ballistic cap (windscreen) and heat treatment to a higher hardness.

One of the responses to my post on the i-mdb.news (Saumur Intranets service), regarding those ballistic tests against Pershing front armor, stated that Russian tests against the cast mantlets on M46, M48 and M60 resulted in the conclusion that American mantlet castings were significantly less resistant than the rolled glacis plate on T55. This is the post by Vasiliy Fofanov in response to my statements: " > While American quality control was improved during October 1943, the low ballistic resistance of the Pershing mantlet raises a number of questions regarding casting quality. This property of US cast armor was well known in USSR and has been found to also be the case in M46 and M48 following trials of these vehicles. I did not see the M60 trial report, but I heard the same was discovered. > When 75mm M72 strikes 3" of U.S. cast armor (Thickness/Diameter=0.98), the casting presented 89.4% of the resistance of 3" of rolled armor. When 90mm M82 strikes 112mm of Pershing mantlet (T/D=1.24), the equivalency is 68%. Based on T/D ratio, the Pershing mantlet thickness multiplier should be over 90%. According to the reports I mentioned, front cast armor elements on M26 and M46 resisted on average by a one third worse than the reference T-55 glacis armor plate (i.e. RHA), using 100mm ATG (BS-3 I presume). This seems in accordance with what is reported here. Best regards, Vasiliy" Good point about the cast mantlets getting smaller and smaller. The Pershing glacis in the American test report did about as well as one would expect from tests, and provided about 94% of the resistance a rolled plate would offer. Not bad, and much better than the mantlet. Maybe all those holes in the mantlet did something unexpected on hits from the openings. The booklet Hammer of God, on the 1973 mid-east war, had some photo's which purported to show that T62 cast turret armor would totally fail on hits that would be unable to penetrate, based on penetration-vs-thickness/angle considerations. What is it with cast armor? Although Tiger and Panther cast mantlets were famous for their ability to take tons of punishment and resist with close to rolled armor capability.

The following is Robert Livingston's response on the Yahoo! Tankers site to several questions that I raised: My answers to Rexford's questions are inserted below: Rexford179@c... wrote: Thanks for the response. Would the following be true, based on your review of the analyzed Panther: 1. a low impact hit, such as U.S. 76mm, could be resisted in a ductile fashion since the surface layer was unflawed and the center area would not crack. YES, but see item 5 below. 2. after a number, maybe one, of sharp impacts a crack could start in the plate interior which would lower the resistance to crack propagation and penetration YES 3. deflected hits that start interior cracking could still appear to be ductile looking on the surface due to unflawed armor YES, the more ductile outer layers could deform or scoop in more ductile fashion. 4. hits from large rounds, such as 122mm and 152mm, might be able to start a crack and take advantage of the fissure during the same hit (one hit with lowered penetration resistance, and an ensuing penetration that would not occur against fully ductile armor) YES 5. It is very good to obtain a metallurgical explanation of how flaws contribute to crack potential and propagation. One important item is that the Panther glacis was not entirely flawed, and contained a good, ductile surface layer. BOTH front and back of the Panther sample glacis were better quality than the center. BHN was 269 at 0-28mm depth, then 262 at 28-53mm, then 269 at 53-83mm. The slight decrease in hardness in the center was accompanied by a drop in Charpy notch toughness from 14.5 ft-lbs in the "good" zones to 11.75 ft-lbs in the brittle zones (at -40degF). Fracture texture was observed to be crystalline throughout the thickness. 6. What would be the implications and probability of fully flawed Panther glacis armor, and have you examined any pictures or penetration descriptions that might suggest flaws extending to the surface. Also, could you suggest why the Panther glacis might contain flaws based on heat treatment? To quote the Panther glacis report: "inferior toughness was attributed to a combination of incomplete transformation to martensite upon quenching and temper embrittlement". The report says that the plate was quenched incompletely, or too slowly, which would leave the center of the plate not sufficiently quenched (transformed to martensite), although the outer sections would be completely quenched to martensite. It is further suggested that the armor may have been tempered in the temperature zone which leads to embrittlement (400-1000degF). This would degrade the quality of the steel in both "good" and "bad" sections, leading to overall poor quality due to brittleness. Thus, the Panther glacis was of adequate hardness, but inadequate toughness, throughout the cross-section. A zone at the center of the section was even more brittle than the outer zones. Roughly speaking, one could call the entire plate "flawed," with an "especially flawed" layer at the center. The US rejected one of its own cast hull fronts after failure in a ballistic test, where 90mm APCBC and AP hits resulted in severe back-spalling. The following Charpy notch toughness was determined: 3.6 to 25.0 ft-lbs at the center, and 12.4 to 29.9 near the surface. At the location of backspalling, the lower values (3.6-12.4) were obtained. The US example above illustrates the actual ballistic results of brittle spots in armor (backspalling) and the wide variability which could be encountered in a single piece of armor. When both Panther and US armor samples were re-heat treated as an experiment, toughness improved markedly. This shows that the BHN was adequate, as was the chemical composition. The problem was in the heat treatment procedure. Source reports for both armor samples described above are contained in the bibliography to Bird and Livingston's _World War II Ballistics: Armor & Gunnery.

A report entitled THE VULNERABILITY OF ARMORED VEHICLES TO BALLISTIC ATTACK, from Aberdeen Proving Grounds, has been reviewed and this post will deal with tests against Pershing front armor. The report is dated September 1950. Page 107 of the report lists the protection ballistic limits against the Pershing glacis and mantlet when attacked by 90mm M82 APCBC. The velocity for 50% penetration success is 2737 fps against the glacis and 1652 fps versus the mantlet center. The 50% velocities relate to effective vertical thicknesses of 168mm on the glacis and only 73mm for the mantlet. Using the slope effects and cast armor modifiers in our book, the effective resistances are estimated at 176mm glacis and 108mm mantlet. The glacis resistance from the firing tests is within 5% of the figure we calculated, but the mantlet resistance is -32% lower. The remarkable aspect of the ballistic test findings is that a 112mm cast mantlet offered 73mm of rolled armor resistance, which suggests potential problems with the casting. While the report recognizes an unbalance in the mantlet and glacis resistance, the magnitude of the difference is not identified or discussed. While American quality control was improved during October 1943, the low ballistic resistance of the Pershing mantlet raises a number of questions regarding casting quality. When 75mm M72 strikes 3" of U.S. cast armor (Thickness/Diameter=0.98), the casting presented 89.4% of the resistance of 3" of rolled armor. When 90mm M82 strikes 112mm of Pershing mantlet (T/D=1.24), the equivalency is 68%. Based on T/D ratio, the Pershing mantlet thickness multiplier should be over 90%. [ 12-16-2001: Message edited by: rexford ]</p>

Larger rounds take advantage of brittle characteristics more than lighter ones. 17 pounder APCBC has a harder nose and strikes at a higher velocity than U.S. 76mm APCBC, so the impact is greater. It's kind of like the difference between throwing small marbles at high velocity at a thick glass wall, and then throwing a brick at a much slower velocity but about the same energy. The glass may deflect the marbles with minimal damage but crack (or shatter) against the brick. Big things take advantage of problem areas better for some reason.

Robert Livingston posted the following on the Yahoo! Tankers forum regarding the ability of the Panther glacis to resist hits in a ductile fashion while being vulnerable to internal crack propagation when hit really hard: ---------------------------------------- "Guilford11 raises an interesting point. Metallurgical analysis in the US during WWII showed a sample of Panther glacis to be flawed in the center. Crystal structure was "bainite" in the center layer, which would be classified as an internal flaw. It is possible that a severe hit on this kind of flawed plate would start cracking, which would be stopped by the outer layer of tougher steel, until hit another severe blow which would cause further migration of the crack through the entire thickness of the plate. This is a common mode of failure of steel railroad rails; one of the methods railroads use for prevention of rail failure is to periodically image the interior structure of the rails from a slow-moving test vehicle. Those interior cracks grow slowly under the repeated stress cycles of supporting heavy wheels. Obviously the Germans didn't examine the Panther glacis this way after it successfully defeated hits in combat, nor did the Allies do radiographic studies of Panther armor which had been hit but not penetrated. But I do suspect that interior flaws in armor would result in cracking after a series of hard hits, even though the armor would appear sound and unharmed on the surface after the first projectile defeats." ------------------------------------------- The Isigny firing test report notes that 2 of 3 Panther glacis cracked after a few hits while the third glacis withstood over 20 rounds without cracking. 17 pounder hits at close range cracked the glacis, 76mm APCBC and HVAP did not.

This thread is intended to draw out all opinions on Panther glacis quality, especially those that differ from mine. So all doors are wide open and previous, as well as future input, is appreciated. Post on Matrix Games forum indicated that Germans may have switched from high quality, "pure" E armor to other types as demands of war placed more and more constaints on tank armor production. We have some German armor plate reports where the 80mm stuff was without flaws in all cases, this is 1942 production and might apply to Tiger. Matrix Games thread on Panther glacis is at: http://www.matrixgames.com/cgi-bin/ultimatebb.cgi?ubb=forum&f=26&SUBMIT=Go One of the questions that came up on another site is whether brittle glacis armor on Panther would resist U.S. 76mm hits in ductile fashion with scoops and no cracks, but show brittle nature against heavier more penetrating rounds. At Isigny France, U.S. 76mm bounces off all 3 Panther glacis plates in seemingly ductile fashion, but 17 pounder is deflected and leaves a crack in two glacis plates at close range. We speculate that the crack would have appeared after the shot bounced away, and may have been due to energy release causing the brittle material to pull apart. Not knowing much about metal, input on this would be appreciated. If the crack appeared as the round dug in, it would seem that the projectile would have stuck in the plate or even got competely through (excuse my English here, but I lived in Brooklyn for awhile). The Russians noted that 122mm AP hits were deflected and gaping holes and cracks appeared in the Panther glacis in reported cases. They do not state what percentage of 2500m or long range hits resulted in dramatic results (although they probably would only see the tanks that fell apart and were abandoned on the field). This is being brought up because a few people have stated that many Panther glacis plates show evidence of rounds being deflected in a ductile fashion, nice clean looking scoops, without cracks or ragged edges. The Matrix Games forum posts also speculate that any flaw tendencies in Panther glacis may have shown up after a certain date during 1944 due to some changes that may have occurred. The British appear to have had much experience fighting Tigers and Panthers, and they assessed the armor quality as good (with an infrequent bad plate here and there). So it doesn't sound like 1943 and early 1944 Panthers were any different from other panzers. The Russians also note similar findings. Just trying to broaden the base of the analysis on the Panther glacis issue. Thanks.

Following info was posted on AFV News and adds some points regarding Panther glacis resistance and ductility on Eastern Front: From Valera Potapov post several years ago on IS-2 ammunition performance: "However, in autumn of 1944 the problem of the poor AP performance of its shots disappeared. Suddenly the performance of the D-25T gun of the IS-2 against the German tanks improved dramatically. The reports from the front described cases where the BR-471 122mm projectile fired from 2500m ricocheted off the front armor of a Panther leaving it in huge holes and cracks". This is a round that previously could fully penetrate up to 600-700 meters and now it is doing substantial damages in more than one event (cases). Sounds like Isigny results, only worse. 17 pounder APCBC results in cracks after ricochets at close range, 122mm does quite a bit more at 2500m (where penetration/armor ratio would be alot less than 17 pounder at 200 yards). The first encounters between IS-2 and Panthers (late fall, winter, early spring?), and tests during January 1944 (dead of winter), resulted in poor performance of BR-471 ammo. Then, during autumn 1944, things appear to change drastically. Your point is well taken, weather and temperature could impact conclusions drawn. The above information suggests that the observed decrease in Panther glacis ductility and resistance was not temperature dependent." As an aside, the first IS-2 tanks appear to have suffered from exceedingly brittle armor which is given as one reason for high loss rates. Tests with 76.2mm ammo resulted in excessive fragmentation and splintering inside the tank. Problems with armor ductility are not limited to Panther glacis, and Sherman cast armor prior to October 1943 was known for brittle, crystalline structure at Brinell hardnesses over 240. Rolled armor on Sherman could also have significant loss in penetration resistance due to flaws and brittle structure.

Thanks for good responses. The possibility of burned out Panthers at Isigny was brought up on AFV News site, and is a valid concern. Isigny report indicates that two Panther glacis cracked after a few hits, so pre-test damage from hits would be minimal. I assume that testers checked glacis for cracks prior to test to assure that test results were valid for generally undamaged armor. The assumption that the testers checked for pre-test damage is one of those issues that is not stated and lots of people feel uncomfortable trusting that the test team considered all sorts of things. Our view is that if reports are thrown out due to incomplete statement of test factors and pre-test precautions one would be left with little or nothing. This is a point Nathan Okun has brought out several times. During other U.S. firing tests, burned out tanks were used to set penetration ranges against captured Panther tanks, and then undamaged tanks were used for final tests. I believe that the final test results were consistent with the earlier tests against burned tanks. Will look further into points raised.

If the statistical analysis is based on a given flaw percentage exactly duplicating the three pieces of data we have (2-of-3 flawed at Isigny, 1-of-3 flawed at Kubinka, 1-of-1 flawed in U.S. metallurgy test, chosen from a random sample), the following are the probabilities for duplication of the three data pieces: 5% of Panther glacis are flawed, 1-in-21,000 10% flawed, 1-in-10,000 30% flawed, 1-in-40 50% flawed, 1-in-14 70% flawed, 1-in-17 80% flawed, 1-in-34 While the samples are small, the statistics suggest that the most likely percentage of flawed Panther glacis armor is around 50%.

The following provides a full description of the research that went into the finding which suggests that a good number of Panther glacis contained flaws and had reduced penetration resistance. References to the book, WW II BALLISTICS: Armor and Gunnery, by L. Bird and R. Livingston occur throughout the post when page numbers are stated: During our research about 10 years ago, we obtained a copy of the Isigny test report for August 1944 from the U.S. National Archives, where two of three Panther glacis cracked after a few hits from 76mm and 17 pounder hits that failed to penetrate (short range hits). This suggests brittle armor with flaws. A report was found on the Russian Battlefield Internet site where three Panthers were fired upon during September 1944. The armor performed like high quality plate against 100mm and 88L71 ammunition, but appears to have lost significant resistance against the 122mm hit. We have U.S. tests of Russian 122mm APBC against homogeneous armor, and the Kubinka result occurs at a greater range than would be expected against good quality ductile armor. This suggests armor flaws. Through the years we have come across many pictures and reports regarding brittle Panther glacis armor, big cracks after AP, APCBC, APBC and HE hits, extensive damage not consistent with good ductile armor, etc. Valera Potapov has published descriptions of 122mm hits on Panther glacis complete with penetration ranges and unusual results that suggest brittle behavior. Through the NTIS we obtained report AD-A954 952, Metallurgical Examination of a 3-1/4" Thick Armor Plate from a German PzKw V (Panther) Tank, January 1945. The annotation in our book on this report is that it concerns "a sample from captured Panther glacis, likely captured in France. Flaws noted". This annotated reference is listed in section c., of the bibliography, which is entitled German, Czech Armor. Page 129. We have also discussed the issue with others who have examined German firing tests and German analysis of their armor during the war. At Kummersdorf during August 1942, German firing tests against 80mm through 110mm plate suggest that the armor had decreased resistance compared to expectations. German authorities suggested that the plate be retested for acceptance. A researcher we discussed the issue with speculated that a good percentage of Panthers had deficient glacis armor. Within the next month we should be receiving detailed German firing test data against Panther armor over a several year period that includes all three Panther models. This data will be analyzed and the results posted on the Internet and in possible errata to our book. As noted by Nathan Okun, reports usually fail to include all the information that is really needed to consider the factors that might impact the results, if one is aiming for 100% assurance in conclusions. We view penetration and armor resistance research in the following manner: On many issues 100% assurance is not possible due to the variations in data and information available to each individual researcher, so one offers a conclusion that may not be accepted by all. The Isigny and Kubinka tests run contrary to the theory that German armor was usually ductile and good quality throughout the war, and the U.S. metallurgical report presents further material to throw into the stew. But there is certainly material to suggest that flaws were not as prevalent as we suggest, which is recognized. But at this point neither side can really be proven with 100% certainty, so both "flaw" theories are neither correct or incorrect, neither right or wrong, since there is no "absolute truth" on the issue (which occurs with many WW II issues). Notes: 1. The probability of exactly duplicating the Isigny results (2-of-3 three glacis are flawed and brittle) follows, based on assumed flaw rates: 1-in-3 chance when 50% of glacis are assumed to be flawed 1-in-37 chance if 10% flaw rate is assumed 1-in-140 chance if 5% flaw rate is used in analysis 2. We have U.S. firing tests against flawed and unflawed armor which suggest reductions in resistance based on the size of the flaw and the projectile diameter compared to plate thickness. Panther glacis with medium flaws should lose about 7.5% of the resistance against 75mm and 76mm hits, which means that the Sherman 75mm APCBC and 17 pounder APCBC should not be able to consistently penetrate a medium flawed glacis at point blank. 85mm APBC might at very close range, but we have not done the calculations. 3. It should be noted that since we used curves of best fit through data, it should be understood that estimates from our book will be subject to variations (we show the variations in slope effect between different U.S. projectiles in the book as a function of diameter and T/D ratio even though we use one equation for 57mm-90mm APCBC). 4. We have compared our estimates with firing test data/battlefield reports in many cases (we analyzed all of the firing test data we could find), and the two are reasonably close. We're either close to the actual with our data or we're lucky, but many people say it's better to be lucky. 5. The Germans tested 80mm armor using 50mm uncapped rounds, which is discussed in Appendix 11 of our book. 50mm hits on an 80mm thick plate may result in flaws not being exhibited through a decrease in penetration resistance, while 75mm and 152mm hits may cause flaws to impact the resistance. It is also possible that 50mm tests for complete penetration damage type (ductile or brittle) may hit areas with weak or no flaws and miss isolated flaw areas.

During 1942, the Germans conducted tests against duplicates of T34 armor which were manufactured by DEW and H. Ei. The report is dated June 1, 1942. 37mm and 50mm guns were used in the tests at 100m range. T34 armor was judged to have the following composition: C, .22 to .25 Mn, 1.30-1.50 Si, 1.35-1.45 Cr, .80-.90 Mo, .15-.25 V, 0.0 Ni, 1.30-1.50 The DEW and H. Ei. compositions varied slightly from the German analysis of actual T34 armor. Armor hardness was above 400 Brinell. Since T34 armor was noted as having variable thickness, the tests were conducted against armor that was supposed to be within the 40mm to 50mm thickness range, although the actual produced test plates varied from 40.6mm to 53.3mm. This post will present the 50mm test results. For analysis purposes the penetration test results are grouped according to estimated resistance at 0 degrees slope, which will aid in determining the penetration probability. Group I, 128mm to 149mm effective resistance at 0 degrees fully penetrates 47.2mm at 60.5 degrees, 149mm effective partially penetrates: 47.1mm at 59.5 degrees, 141mm effective 47.7mm at 59.0 degrees, 140mm effective 53.3mm at 55.5 degrees, 140mm effective 50.4mm at 55.0 degrees, 128mm effective fails to generate crack on plate back 51.9mm at 54.5 degrees, 130mm effective 53.0mm at 55.5 degrees, 139mm effective 45.8mm at 59.0 degrees, 133mm effective Group II, 161mm to 183mm effective resistance at 0 degrees fully penetrates 42.1mm at 65.0 degrees, 161mm effective partially penetrates: 45.8mm at 65.0 degrees, 180mm effective fails to generate crack on plate back 43.2mm at 65.0 degrees, 167mm effective 47.1mm at 64.5 degrees, 182mm effective 47.2mm at 64.5 degrees, 183mm effective 47.7mm at 64.0 degrees, 181mm effective 53.3mm at 60.5 degrees, 173mm effective 53.0mm at 60.5 degrees, 172mm effective 50.4mm at 60.5 degrees, 162mm effective 51.9mm at 60.0 degrees, 161mm effective The next posts on this thread will analyze the data. Note: slope effects for 50mm APC derived from equations in WW II BALLISTICS: Armor and Gunnery, by L. Bird and R. Livingston, Overmatch Press, Albany, NY and Woodbridge, CT, 2001.

We note that Duplessis' article is posted on the Saumur Intranets web site at: http://musee-des-blindes.intranets.com/r.asp?a=5&id=13532 Log on as a visitor and the site will take you to the article. Otherwise, Rexford notes that the article is in Volume 35, No. 3, if he copied the numbers correctly, which knowing him well, I think he got correct.

Based on a trajectory equation and data for U.S. HC and WP smoke, the following first shot hit probabilities were calculated against a 2.25m high target (average of 2m and 2.5m target height): 150m, 100% for both rounds 200m, 89 for HC, 95 for WP 250m, 68 for HC, 80 for WP 500m, 17 for HC, 23 for WP 750m, 7 for HC, 10 for WP 1000m, 3 for HC, 5 for WP 1372m, 1 for HC, 2 for WP 1829m, 1 for WP The above analysis assumes no winds, level ground and range is limited by maximum gun elevation to 1372m for HC smoke and 1829m for white phosphorus. Muzzle velocities assumed to be 850 fps for HC and 925 m/s for white phosphorus (figures derived from Duplessis' article in AFV News). The hit probabilities have also not been modified for first shot drift and jump, which would primarily impact the longer range attempts where the hit probabilities are low anyway. The computed hit chances suggest that offensive use of smoke via direct hits would be best attempted at close range if the situation demanded a first shot hit (Tiger or Panther is about to rotate turret onto a Sherman). One of the benefits of slow moving high trajectory rounds (like U.S. smoke, which appear to be fired at under 950 fps) is that the shells do not have a lengthy ground scatter pattern due to vertical dispersion. So smoke rounds can be accurately and effectively "walked" onto a target vicinity if one has the time (and nerves) to change range settings and correct for fall of shot while an enemy may be trying to stop you. Due to the high trajectory, the chance of hitting vertical targets at longer ranges would be limited, which will be the next computations we will carry out. The figures for first shot accuracy with smoke rounds are based on an average range estimation error of about 20% that varies from 0% to 60% according to a bell shaped distribution curve. Based on past e-mails with Conall, 100% accuracy may only be attainable by relatively few gunners and crews due to the effects of stress, fatigue and sloppy aim. When 88L71 misses with Jagdpanthers occur at 500m against fully exposed vehicles, it is not due to bad range estimation errors but totally incorrect aim (uses wrong range line on scope, fails to put cross hairs on target, etc.). Conall has recommended in the past that all computed hit probabilities be multiplied by a given factor that considers actual combat reactions instead of mechanical, robot like performance: 90% for elite crews 85% for vet 80% for experienced 75% for regular 65% for green 50% for militia might be assumed for wargaming and approximate research analysis purposes. Smoke shell accuracy would, of course, be increased on follow-up shots or if previous hit attempts with armor piercing or high explosive shell had hit the target, which identifies the correct range to use. However, since AP, APCBC and HE rounds would have flatter trajectories than smoke, the flatter trajectory ammo would be able to hit with small range estimation errors which would result in misses with smoke. For example, a 550m range estimation against a target at 500m with 75L40 APCBC puts the round 0.35m over the intended aim point (usually the center of observed target mass). If white phosphorus or HC smoke is aimed at 550m against a target at 500m, the round goes 1.91m over the target center for a miss. To hit a target on the fly at 1000 yards with smoke takes a very close range estimation error or a bit of luck (which is sometimes better than skill). P.S. If white phosphorus is fired at a greater muzzle velocity than 925 fps than the relative accuracy would be higher, and possible corrections to the velocity I used would be appreciated.

Thanks for great info, which is appreciated. Michael Duplessis' article has 3 kg for M89 HC smoke round, and 3.3 kg for WP, as opposed to nearly 6.8 kg for 75mm APCBC-HE-T. Combining light weight, flat nose and low muzzle velocity (850 fps for HC, about 925 fps for WP), makes first round direct hits problematic The possibility of the British having 75mm smoke for French 75 available for Grants, Lees and Shermans is a very good comment. I will ask Robert McNamara about his smoke recommendations in Advanced Squad Leader. Thanks again for several good responses.

When Advanced Squad Leader indicates that Grant, Lee and Sherman tanks in British use had smoke rounds from the very start of their use, this implies that the British made the smoke ammunition and would have started as soon as their acquisition of 75mm armed tanks was envisioned. Cause the U.S. did not use 75mm smoke till Normandy, if ASL is correct. Can anyone verify that the British made 75mm smoke rounds during 1942 and made it available to their U.S. built tanks? Thanks.

Thanks, Cap Wacky.

When Sherman tanks with 75mm fired smoke rounds at a target that was estimated to be at 600m, would they try to drop the round in front of the target and thus estimate range at 600m but set first shot for 100m or 200m less to avoid firing over the target range. We're developing a detailed set of armor miniatures and want to give smoke use a good system, so detailed info would be very valuable. I have FM17-12 for Tank Gunnery but it is dated April 22, 1943, prior to availability of smoke for Sherman tanks. One other question, why did Americans wait so long to develope smoke? One source I have says no Sherman smoke till June 1944. German 75L24 had smoke from start of war, so did StuG III. Advanced Squad Leader indicates that British tanks with 75mm gun (including Grant, Lee, Shermans) always had the possibility of carrying and using smoke. Yet Americans wait till Normandy. Anyone know why? Not having smoke would place American Shermans in a less desirable position than British when they faced Tigers and PzKpfw IV in Nord Afrika.

Being over 50, things sink in very slowly most of time. The Sept.-Dec. 2000 issue of AFV News had what appears to be one of the premier articles on U.S. smoke shell usage. The article is entitled: AMERICAN SMOKE: An Underdog Battles the Big Cats, is by Michael Duplessis, and is a great read from start to finish. A summary follows: 1. While the Eisenhower report destroys the comparative worth of most U.S. equipment compared to German, American smoke shells get an A+. Report site is at: http://www.hitechcreations.com/ubb/Forum9/HTML/000686.html 2. American tankers used smoke aggressively and offensively. Smoke shell direct hits on panzers could blind for as long as 4 minutes. Smoke would be carried in barrel as ready round in case a threat suddenly appeared. 6 of 15 ready rack rounds could be smoke. 3. German tankers on record as stating that American smoke rounds were excellent and exceptionally accurate. The exact phrase they used is "maddeningly accurate". 4. White phosphorus is not a Sherman tank standard ammo load but was designed for M1A1 Pack Howitzer, and it could be chambered by 75mm Sherman M3 gun. WP is not listed on the gun tables in Hunnicutt's SHERMAN. Great accuracy in firing smoke rounds is an odd one. The 75mm smoke round weighed 3 kg (6.6 pounds compared to about 15 for APCBC), had a flat nose (really poor ballistically but avoids digging into ground), and was fired at 850 fps (259 m/s) which assures a high trajectory and poor first shot hit probability. Hitting a Tiger on the fly with a smoke round at 600m might take quite a few shots, if one could see through the smoke cloud. We never use Sherman smoke rounds in our miniatures games, and that really may not be very realistic. Based on Duplessis' article smoke rounds were the mainstay of many tanks when they came across, or were attacked by heavy German armor. The only consolation for the panzer guys is that American smoke seems to only become available during and after June 1944. We believe that the large kill ratio's for the Tigers in Nord Afrika in tank battles was helped by an absence of American smoke ammo for the Sherman, plus some problems with Sherman optics and training and crew experience and on and on. What is perplexing is that there are many AAR where Shermans pelted Panthers and Tigers with armor piercing rounds and HE shells and nothing is said about smoke being flung around. There would almost seem to be wide variations in the degree to which smoke was valued and used from unit to unit. Were smoke rounds used in a uniform manner between American units? How wide would a smoke cloud typically get in a light wind? How long till smoke cloud develops and would block line of sight and fire? Duplessis indicates that HC smoke shells did not burn hot so they stayed close to the ground. We're going to give our Shermans 4 or 5 smoke rounds apiece in some miniatures games and see how the panzers do. Or else we'll just stick to pre-6/44 games.

The problem with tank machine guns is range. ASL gives the bow machine gun on a tank 320 meters normal range, and 480m for coaxial MG. Beyond that range firepower factors are halved. When Shermans meet up with 88mm Flak guns at 2000m, the Shermans have to resort to the HE, which reportedly was effective in dealing with the monster flak guns in Nord Afrika. Within 300m or so it seems best to use machine guns in ASL, and maybe in "real life". Having a good machine gun atop the turret probably helped Sherman crews alot, Band of Brothers showed Sherman commanders manning the AA machine gun during a counter-attack on a German position. Would an exposed tank commander firing the AA machine gun from OUTSIDE the turret (standing on rear hull deck) detract from the tanks command control? The Band of Brothers episode seemed to have the commander standing on the deck as he fired, as opposed to within an open hatch. [ 12-02-2001: Message edited by: rexford ]</p>