rexford

Following up on an earlier thread regarding the German penetration data in CMAK, British Ordnance Board curves present the following figures for German guns and ammo against vertical plate (British muzzle velocities adjusted to agree with German figures: British had 2300 fps for 75L43 APCBC, two velocities other than 3280 fps for 88L71 APCBC and 2700 fps for 50L50 APC): 50L42 APC (2240 fps muzzle velocity) 100m 72mm 500m 58mm 1000m 43mm 1500m 33mm 50L60 APC (2739 fps muzzle velocity) 100m 97mm 500m 78mm 1000m 59mm 1500m 45mm 75L43 APCBC (2427 fps muzzle velocity) 100m 133mm 500m 118mm 1000m 102mm 1500m 89mm 75L46 APCBC (2600 fps muzzle velocity) 100m 145mm 500m 131mm 1000m 115mm 1500m 101mm 75L48 APCBC (2460 fps muzzle velocity) 100m 136mm 500m 121mm 1000m 105mm 1500m 91mm 75L70 APCBC (3067 fps muzzle velocity) 100m 184mm 500m 166mm 1000m 146mm 1500m 128mm 88L56 APCBC (small HE burster and 2558 fps muzzle velocity) 100m 153mm 500m 141mm 1000m 127mm 1500m 1144mm 88L56 Flak 36 APCBC (large HE burster and 2600 fps muzzle velocity)) 100m 140mm 500m 130mm 1000m 118mm 1500m 107mm Note: Data in Thomas Jentz' DREADED THREAT suggests that early war 88mm Flak ammo penetrated less than the above figures, and data presented by Chamberlain suggests an 810 m/s (2657 fps) muzzle velocity for Flak 18 APCBC based on comparion with Tiger 88mm small burster APCBC at 780 m/s. 88L71 APCBC (small HE burster and 3280 fps muzzle velocity) 100m 216mm 500m 200mm 1000m 182mm 1500m 166mm The British curves also seem to underestimate German velocities at range, which could lead to lower than actual penetration figures. We used the German velocity-range data to prepare the following estimates which use the British 0m penetration data: 75L46 APCBC 100m 146mm 500m 133mm 1000m 119mm 1500m 106mm 75L43 APCBC 100m 136mm 500m 121mm 1000m 108mm 1500m 96mm 75L48 APCBC 100m 135mm 500m 123mm 1000m 110mm 1500m 98mm 75L70 APCBC 100m 185mm 500m 169mm 1000m 150mm 1500m 134mm 88L56 APCBC (tank gun ammo with small HE burster) 100m 153mm 500m 143mm 1000m 131mm 1500m 120mm 88L71 APCBC 100m 217mm 500m 208mm 1000m 191mm 1500m 178mm [ March 09, 2004, 10:23 AM: Message edited by: rexford ]

If memory serves me, David Fletcher from Bovington Tank Museum wrote a book on Churchill tanks. Did he discuss 6 pdr use of APCR? Excuse me if my memory is totally off the wall, been feeling my age lately.

Reviewing Russian penetration figures at close range, we found that the effectiveness of the rounds drops off as the range decreases and the impact velocity increases. For the 76.2mm L41.5 APCR, vertical penetration is: 60mm at 1000m 92mm at 500m 98mm at 300m 102mm at 100m A 32mm difference in penetration from 500m-1000m but 10mm from 100m-500m, which suggests that the round is failing structurally as the impact velocity increases. Normally, the change in penetration per given interval increases as the range decreases, which it does in American, British and German data for tungsten core ammo. Results similar to Russian 76.2mm APCR were found for 45mm M37 and M42 APCR, where the penetration effectiveness appears to be blunted and reduced as the range decreases. Using the available data the following vertical penetration figures were generated: 76.2mm 41.5 APCR ================ 104mm at 0m 102mm at 100m 100mm at 200m 98mm at 300m 95mm at 400m 92mm at 500m 88mm at 600m 83mm at 700m 76mm at 800m 69mm at 900m 60mm at 1000m 45mm L46 M37 APCR ================= 96mm at 0m 89mm at 100m 82mm at 200m 75mm at 300m 69mm at 400m 64mm at 500m 57mm at 600m 50mm at 700m 45mm at 800m 40mm at 900m 35mm at 1000m 45mm L66 M42 APCR ================= 111mm at 0m 101mm at 100m 93mm at 200m 85mm at 300m 79mm at 400m 72mm at 500m 67mm at 600m 60mm at 700m 53mm at 800m 47mm at 900m 42mm at 1000m References: 1. Russian April 1943 firing tests vs Tiger ============================================ 45mm M37 APCR penetrates side at 200m 45mm M42 APCR penetrates side at 350m 76.2mm L41.5 APCR penetrates front at 500m on some hits 2. Russian "Instruction on fighting German tank T-VI", April 20, 1943 ======================================= 45mm M37 APCR penetrates side at 200m 45mm M42 APCR penetrates side at 500m and front at 100m 76.2mm L41.5 APCR penetrates front at 100m Above results appear to be based on calculations from published penetration data and the report predates actual firing tests against Tiger. 3. British A.R.D. Sketch "Penetration Curves of Russian Weapons, 30 Degree Attack (According to Russian Data)", Nov. 1946 =========================================== 45mm M37 APCR at ranges from 100m to 491m. 4. Russian Battlefield table on "The Armor Penetration of the Soviet Tank Guns" =========================================== 76.2mm L41.5 APCR defeats 102mm at 100m, 98mm at 300m and 92mm at 500m The Russian penetration figures for 45mm M42 APCR of 80mm at 500m and 52mm at 1000m appear to be questionable, since they are not consistent with 350m penetration range during April trials and are not consistent with 45mm M37 APCR penetrating 80mm at 200m (which is consistent with trials against Tiger). The penetration estimates for 45mm M37 and M42 APCR were adjusted to equal 82mm penetration at 200m and 350m range to be consistent with the April firing test results against Tiger.

First, what is the slope of the 75mm side hull armor on KV tanks? Vertical, of course. 0 degrees from vertical. We can extrapolate from 122mm APBC tests to 76.2mm APBC because the math is based on slope effect for a given T/D ratio. 45mm is to 76.2mm as "x" is to 122mm. 45mm T34 armor is higher hardness than KV-I 80mm medium hardness, and given a certain slope effect for a given T/D ratio one can determine equivalent resistance in terms of medium hardness plate. Which is what I did. 45mm at 60 degrees resists 76.2mm APBC like 90mm vertical if it is medium hardness, but the Russians found that the 45mm high hardness plates were defeated at the same velocity as 80mm vertical. So 45mm high hardness is less effective than medium hardness against 76.2mm APBC.

Pavel from the Russian Battlefield Forum (and Yahoo! Tankers) site found a reference to a 1942 Russian firing test with a 76.2mm Russian gun against the glacis of a T34. The finding was that the T34 glacis resisted 76.2mm hits like 80mm of medium hardness armor from a KV-I tank. Going from the U.S. tests with 122mm APBC against medium hardness armor, when 76.2mm APBC rounds hit 45mm medium hardness plates at 60 degrees from vertical the resistance should be the same as a 90mm medium hardness vertical plate. Since the T34 glacis was equivalent to an 80mm plate in the Russian tests, this suggests that the T34 glacis armor acted like 45mm of good quality medium hardness plate x (80mm/90mm). In other words, the high hardness T34 glacis resisted hits by 76.2mm APBC with 11% less resistance than medium hardness armor. Due to the difference in nose shape and caps between 76.2mm APBC and 75mm APCBC, the Russian result would not strictly apply to German ammunition. But the Russian test shows that 45mm T34 plates lose resistance compared to medium hardness armor when they are hit by good sized projectiles. When German 75mm APCBC hits T34 glacis plates the 45mm plates would resist with -24% less resistance than medium hardness plates. The above results may have a significant impact on the way CMBB models T34 hits with APBC ammo on the front hull of T34 tanks, as well as side and rear hits. Firing the standard BR-350B APBC round, T34 hits on the T34 glacis would only be able to penetrate completely at very close range. [ February 25, 2004, 07:03 PM: Message edited by: rexford ]

ANALYSIS OF RUSSIAN PENETRATION CURVES The Russian Battlefield web site provides penetration curves for Russian and Lend Lease tank guns in use during WW II, where the graph is available at http://www.battlefield.ru/library/archives/weapons/pics/penetration.gif. The following discussion attempts to fill in the missing information regarding armor type and success criteria, and provides some cautions on the use of the curves. 1. The plots for 57mm thru 122mm guns are straight lines, whereas the data should present a curve 2. Comparison of the Russian penetration data for 75mm M72 (M4A2) and 6 pdr (Mark IV) guns with Allied figures suggests that the armor type is homogeneous, the Russians are using the Initial Penetration criteria (20% of hits succeed) and one data point at 500m has been extended to other ranges using a straight line approach 3. The curves for Allied 40mm and 37mm penetration show extreme fall-off with range and are questionable due to zero slope at 1150m (no change in penetration with range) 4. The Russian 20% IP criteria can be converted to 50% success using a 0.9443 multiplier Applying expected penetration-vs-velocity-vs-range profiles for stated or likely ammunition types with the above assumptions results in the following revised penetration figures for Russian use tank guns (homogeneous armor, 50% of hits succeed): 1. 6 pdr (APC): 102mm at 100m, 85m at 500m, 68mm at 1000m 2. 76.2mm F-34 (APBC): 78mm at 100m, 69mm at 500m, 59mm at 1000m 3. M4A2 75mm (M72 AP): 108mm at 100m, 92mm at 500m, 76mm at 1000m 4. 122mm (APBC): 207mm at 100m, 189mm at 500m, 167mm at 1000m 5. 85mm (APBC): 136mm at 100m, 120mm at 500m, 102mm at 1000m The above estimates are consistent with Russian firing tests against the 80mm design spec side armor on Tiger tanks during April and September 1943, where the 6 pdr tank gun had a 600m penetration range and APBC fired by the 76.2mm T34 gun failed to defeat the Tiger side armor at 100m and 200m range on perpendicular hits. Analysis of 20 firing test results against the 80mm design thickness side plates on Tiger suggest that the average plate resisted penetration like 84.5mm of good quality armor (increased resistance due to combination of thicknesses above 80mm and improved ballistic response) .

The Tiger mantlet varied widely in thickness. 135mm to 140mm or so around the gun and in the middle two-thirds or so of the flat areas, down to 97mm at the upper and lower edges. Maximum Tiger mantlet thickness close to 200mm at the trunnion mounts. But the upper and lower edges were backed by a 100mm armor casting. The area immediately around the vision openings for the gunner was 75mm thick or so on the early Tigers due to a hollowed-out area, but was reinforced on later Tiger tanks. The above is what is meant by reinforced turret front.

The American and British penetration figures presented in CMAK seem to be mostly face-hardened armor values, while the German are most likely homogeneous since no Allied tanks carried face-hardened after the early Stuarts. The above stats for Panther 75L70 work out to 199m at 0m and vertical. Seems high. British stats for Panther APCBC at 0m have 188mm, our computations are about the same. British have Tiger APCBC doing 156mm vertical at 0m, CMAK seems to be much higher. Brits have about 138mm vertical for 75mm L48 APCBC at 0m and 0 degrees, our calcs are about the same, CMAK is much higher. German face-hardened armor resisted about the same as American face-hardened for tanks, which was about the same as British, where Americans and Brits made and fired upon thick face-hardened plates for penetration data to compare with German tanks. Germans used face-hardened armor on: PzKpfw III front hull and turret, hull rear PzKpfw IV front hull and turret Panther D all over the hull and early Panther A (front hull and hull side) StuG IIIG and IVG front and other vehicles The CM penetration models seem to change from game to game as they improve them. The Germans used alot of tanks with face-hardened armor in France, but CMBO uses homogeneous armor penetration stats for Allied guns. But they overstate Allied penetration in quite a few cases because they equate Allied ammo quality as equal to German. In CMBB the realization surfaces that face-hardened panzers and homogeneous armor on panzers requires two sets of penetration stats for Russian and Allied lend-lease weapons. In addition, it is recognized that American ammo was softer than German and carried larger HE bursters, so Sherman 75mm APCBC and PzKfw IVH 75mm APCBC penetrate different amounts of homogeneous plate at 619 m/s (German penetrates about 15% or so more). Russian ammo in CMBB is recognized as being much softer than American (50 average Rockwell C noses on Russian vs 54.5 on American vs 63 on German), and flat nose Russian APBC penetrates even less on low angle hits due to nose shape. Although APBC flat nose has much lower slope effects than APCBC as the angle increases. The above is a summary of what I've seen thru the various games.

Thanks.

American APCBC for the Sherman 75mm did not change any from 1942 through 1945 in terms of penetration capability, based on the figures I've seen and the firing test results that are available. During a British test against a captured Tiger in Afrika, 75mm APCBC from a Sherman penetrated the Tiger 80mm design thickness side hull at 17.5 degrees angle and 100 yards range. In another British test, 75mm APCBC penetrated the Tiger side hull (80mm design thickness) at 800 yards with no side angle to the hit. Based on an analysis I conducted of 20 firing test results against the Tiger 60mm and 80mm design thickness plates, those Tiger plates resisted with an average effective thickness of 84.5mm and 63.4mm after comparison to penetration data. Given that the average Sherman 75mm APCBC round penetrates 82mm vertical at 500m, a typical Sherman firing on a typical Tiger tank would defeat the 80mm design thickness side armor on a small percentage of the hits at 500m. In CMBO, Shermans with 75mm APCBC penetrate 89mm vertical at 500m and Tigers have 80mm side armor, so side kills are maybe a little higher than one would expect from our analysis. During the combat where Michael Wittmann was killed by a 17 pdr round, the Sherman 75mm crews reported that their rounds bounced off the Tiger side armor at about 800 yards. While the average Tiger 80mm design plates resisted like 84.5mm, they could vary in quality with 16% resisting like less than 80mm and 16% resisting like more than 90mm. The higher Sherman 75mm APCBC penetration in CMAK is due to the publication of face-hardened figures for the round instead of homogeneous armor performance. Sherman 75mm APCBC penetrates about 82mm of homogeneous armor plate at 500m and about 95mm of face-hardened plate, with the difference being that an armor piercing cap protects the nose from the shattering effects of face-hardened armor so the round is more devastating against that type of armor. Regarding why the German penetration figures went up in CMAK for 75L43, 75L48, 75L70 and 88L56 APCBC compared to CMBB, I don't know. Our book uses lower figures. Where are you people getting CMAK figures for the Panther 75L70? What is interesting is that the 75mm M72 AP solid shot used by the early Shermans could penetrate about 92mm of homogeneous armor at 500m, which made that round vastly superior to the 75mm APCBC against Tiger side and rear armor. The U.S. eventually phased out 75mm M72 AP due to the following issues: 1. ammo tended to shatter 2. no HE burster so less damage and crew injuries 3. no windscreen so it lost velocity FASTER than 75mm APCBC 4. no armor piercing cap so ALOT less face-hardened penetration than 75mm APCBC 5. powder charges tended to vary alot The Americans were going to toss thousands of 75mm M72 AP rounds but someone decided to drill out an HE burster cavity and place caps on the round, which became a APCBC projectile. The German 75mm capped round had superior face-hardened armor performance compared to Sherman 75mm AP and APCBC, and the British used those German rounds in their Grants, and may have used them in Lees and Shermans, based on the limited materials I've seen. In British tests against a PzKpfw IIIH with a Grant (Cairo, May 1942), 75mm M72 AP barely got through the front hull armor at 500 yards while 75mm APCBC just barely defeated the frontal plates at 1000 yards. The German 75mm capped round defeated the PzKpfw IIIH hull front at 1000 yards with plenty to spare. Lorrin [ February 18, 2004, 06:47 PM: Message edited by: rexford ]

Great photo's, thanks so much for posting em. I assume the Tiger was not fully loaded at the time. How much do you think it would sink down into the suspension with a crew, ammo, interior facilities and fuel/oil/water? Asked the above question to get an idea of how much smaller the area between the wheels and 80mm side superstructure armor would become with a normal combat loading. Terrific photo's, good of you to share. Lorrin

The Russian Battlefield site has a penetration curve in the Archives section that I think has homogeneous armor figures, but am not sure. Could someone translate into English the writing on the top of the table at: http://www.battlefield.ru/library/archives/weapons/pics/penetration.gif I'am doing a short research article on those penetration curves and need to know if they disclose anything about the armor type. Thanks. Lorrin

Sir, Some time back you posted some numbers on the total 6 pdr rounds by type sent to Russia, do you have those figures available for posting on this thread. We recently bought nine 1/87 scale Churchills and want to fight them on the Eastern Front in our miniatures games against Tiger. It would be good if we had an idea of the relative proportions of 6 pdr AP, APC and APCBC that might be available during 1943. Regarding 6 pdr APCR use in Africa and Italy, have you ever seen any data on what percentage of 6 pdr armor piercing ammo it made up during 1943? A few sources say no 6 pdr APCR or APDS made it to Russia. Thanks for any help you can provide. Lorrin

The data that we obtained on German ammo scatter showed the Tiger with smaller dispersion than the Panther round. The data was from a WW II German source, and consisted of trajectory sheets with all sorts of information. Like anything else, there are often multiple sets of the same sort of data, perhaps with different dates, that show revisions and changes. Tests are rerun, different lots of ammo are used, etc. It is quite possible that there are two different sets of data for 88L56 and 75L70 scatter that show opposite comparative results. The results that Mr. Tittles compares are close enough that a small change could reverse the "winner".

Yup. That's the article which included some stuff on CMBB. I recently did some graphical additional work on the high hardness modifiers, 37mm Pak AP has about 1.26 multiplier versus 45mm T34 plates (plate resists like 45mm x 1.26 of good quality medium hardness plate). The 50mm Pak 38 APC will have about a modifier of about 0.95 (45mm x 0.95), and around 1.05 against T34 65mm turret side on M42 versions (65mm x 1.05). Spring 1942 German tests showed that 50mm Pak firing APC penetrated KV-I 75mm/30 degree driver plate between 100m and 200m, and 37mm Pak firing APCR penetrated T34 65mm/30 degree turret side at 100m (listed penetration for 37mm APCR is 64mm at 100m, so high hardness is about same as medium hardness against small tungsten core).

There was a reason for developing the 88L71 of the Kingtiger, so this gun was better. </font>

Kip, Was reading an article on the web that you wrote on the CM penetration stats, and thought the following might interest you. Penetration of WW II rounds into vertical homogeneous armor is a function of the following factors: 1. Nose hardness (harder noses penetrate more, in general) 2. Nose shape (pointed noses penetrate more than flat noses) 3. HE burster size (larger bursters weaken the structure and decrease penetration) 4. Armor piercing caps (absorb energy and decrease penetration) 5. Quality (brittle structure supposedly hampered Russian 45mm early in war, U.S. 75mm AP contained irregular powder charges and had a tendency to shatter, and U.S. 76mm APCBC had a tendency to shatter fail when it should easily penetrate due to low shoulder hardness behind the nose which lead to bulging) For WW II ammo, the average German APCBC nose hardness was highest at 63 Rockwell C, with American APCBC at 54.5 and Russian APBC at 50. German 75mm L48 APCBC penetrates about 105mm of vertical rolled homogeneous plate at 619 m/s, U.S. 75mm APCBC penetrates 91mm, due to the American round having a softer nose and a larger HE burster cavity. Russian APBC had a flat relatively soft nose which significantly lowered vertical penetration against homogeneous armor, and the effectiveness against 30 degree sloped armor was also impacted. April 1943 Russian firing tests with 76.2mm BR-350A and BR-350B APBC against Tiger 82mm side armor resulted in no penetrations at 200m with a 0 degree impact angle, and the shots failed at 100m during September 1943 trials. The Russians increased the nose hardness o a limited number of production 76.2mm APBC rounds and the penetration climbed by about 10%. The Russian flat nose APBC does not follow the DeMarre equation (penetration proportional to velocity raised to 1.43 power). With regard to nose shape and caps, 17 pdr uncapped AP penetrates more than 200mm vertical plate at 2900 fps while 17 pdr APCBC penetrates less than 180mm. While armor piercing caps decrease homogeneous armor effectiveness they boost performance against face-hardened armor and may protect rounds from shatter.

John Salt's data provides an interesting comparison of Sherman 75mm AP and APCBC that reverses the traditional penetration relationships. Because 75mm M72 solid shot AP did not have an HE burster and had a pointed nose, it outpenetrates 75mm M61 APCBC against homogeneous armor (100m and 500m) in all the data I've ever seen. However, British report WO 185/178, dated 1943, shows 75mm M72 AP penetrating 88mm of homogeneous armor at 500 yards and 75mm at 1000 yards, while 75mm APCBC defeats 94mm at 500 and 85mm at 1000 yards. U.S. data for 75mm M72 AP has 92mm at 500m and 76mm at 1000m, which is slightly higher than the British report but fairly close. Where are the Allies getting 94mm/0 degrees for Sherman 75mm APCBC at 500 yards in one case, and 100mm/30 degrees at 600 yards in another? TM9-1907 has 81mm/0 degrees at 500m for 75mm M61. Looking like alot of bogus and overinflated penetration stats floating around for Sherman 75mm in days leading up to and slightly after D-Day.

That possibility is not possible given the data in the report. The 75mm M61 penetration against vertical armor is 81mm at 500m, the SHAEF report appendix has 100mm at 600 yards (549m) for M61 APCBC. Someone did something really unbelievable and no one caught it prior to publication.

The Tiger 88L56 APCBC round was superior to just about every other WW II projectile in terms of round to round random scatter. If one aimed the 88mm at a target and did not move the aim, the shot impacts would be close together. Fletcher's book on Tiger tanks notes the findings from a British test of constant aim scatter. But random scatter is not the major issue for WW II first shot accuracy. Battlefield accuracy during WW II brings into play something that is not a problem with Abrams tanks, namely range estimation for the first shot. The average tank crew on a firing range would average a 25% error at all ranges from the actual on their first estimate, where the errors would spread around 0% error according to a bell shaped statistical curve. Tiger crews were expected to estimate first shot ranges to within 10% of actual during their training. Using the Tiger velocity-vs-range and random scatter characteristics we calculated the first shot hit percentages against a 2m high x 2.5m wide target assuming 10% and 25% average range estimation errors: 10% average estimation error ============================ 97% at 500m, 79% at 1000m, 40% at 1500m 25% average estimation error ============================ 93% at 500m, 42% at 1000m, 18% at 1500m The above figures assume that the gun sight is perfectly aligned with the gun barrel, the gunner elevates the gun to the estimated setting, wind effects are negligible, the first shot corrects for jump and other effects, the tank is on level ground so trunnion cant does not come into play, the ammunition is highest quality, the target profile is clearly seen against the background, etc. What actually occurred on the battlefield could vary quite a bit from the above ideal calculations. While a crew might obtain a 10% or less estimate error on the proving grounds against wooden targets, having to hit something that is trying to hit you back brings new issues into play. There is a scene in the movie Glory where a recruit is routinely hitting the target with musket shots while everyone stands around and laughs, so the commander goes over and demands that the rifleman fire accurate shots as fast as he can and all the while the commander is yelling at the soldier to shoot faster and firing his pistol. The recruits firing technique fell apart when things got hectic and loud. There is a combat report, which may be in Jentz' Dreaded Threat book on the "88", where a number of 88mm Flak guns took on a group of Russian tanks at 1200m or so. The final tally resulted in about 10 to 12 shots per knocked out tank. Research by Miles Krogfus noted that a few Tigers usually accounted for most of the kills in an engagement, and reports by Tiger commanders indicate that gunner skill was very important when it came to hitting targets. Some gunners missed easy targets at moderate ranges. On the other hand, a Russian vet who fought with 76.2mm field guns noted that Tigers and Elefants would sometimes knock out their guns at 1200m range with the first shot.

John Salt has done a bang up job of finding and posting a horde of British, and American and other nation penetration stats for WW II. The following data from Salt's compendium provides some silly Allied data that may have gone into the decision to emphasize 75mm Shermans instead of 76mm Shermans: WO 219/2806, Appendix G to SHAEF/16652/GCT/Arty July 11, 1944, penetration data at 30 degrees strike: US & Br 75mm M61 APCBC ======================= 100mm at 600 yards, 93mm at 1000 yards, 82mm at 1600 yards US 76mm APCBC M62A =================== 97mm at 600 yards, 90mm at 1000 yards, 80mm at 1600 yards Salt notes that a memo in the document states that there seems "little to choose" between the 75mm and 76mm. Given that the 75mm and 76mm APCBC rounds were fired at 619 and 792 m/s respectively, and the 76mm ammo outweighed the 75mm by 15.44 to 14.96 pounds, one would think that someone would have figured out that 75mm APCBC could not outpenetrate 76mm APCBC at all ranges before the info found it's way into an official document. Assuming the above data is correct means that the Sherman 75mm could penetrate the Tiger driver plate at 500m with a 30 degree side angle! And the Tiger 82mm side plates would be vulnerable to 75mm APCBC at 1600 yards and a 30 degree side angle! I checked the American stats for aircraft use of the Sherman 75mm gun, which added 350 mph to the muzzle velocity, and the 75mm M61 would still not outpenetrate 76mm M62.

oM is ohne Merkmal. Which means what? Thanks.

German rolled armor specs did not allow plate thicknesses below the design spec, and the max allowable thickness was supposed to be +5%. That's what it supposed to be. The Americans measured a 60mm design spec front lower hull plate on Panther at 66.7mm, and the Russians and British routinely assumed an 85mm glacis thickness during their penetration range estimates vs Panther. Russian 45mm design spec plates show a wider range than German armor, where we have seen actual measurements as low as 42mm and as high as 60mm. Jeff Duquette measured a T34 glacis within the 50mm-55mm range. The Americans didn't care how thick their cast armor was as long as weight restrictions were met, and two of the 89mm design thickness mantlets for 76mm armed Shermans measured 98mm in both cases.

Thanks for all the responses, which sre very helpful. I'll get my copy of the report and post the statements and prior translation regarding oM. It is amazing that the 50mm L60 gun obtained complete and partial penetrations of a 42.1mm plate at 65 degrees slope from vertical, range about 100m. We think the 50mm gun used uncapped AP of highest quality, the report doesn't seem to be very specific about the ammunition. It appears that the 37mm and 50mm anti-tank guns had plenty of APCR during the spring of 1942, so we thought at one time the German firing trials were using APCR. But the 37mm rounds penetrate more T34 high hardness armor than German face-hardened armor, so we're not sure. Thanks again.

The resistance of high-hardness armor needs to be converted to medium hardness plate, since penetration data for rolled homogeneous armor is medium hardness. High-hardness armor is best against small diameter projectiles, and becomes progressively less resistant as the ammo gets bigger. This happens because high hardness armor has low impact resistance and the metal structure is crystalline, which tends to be brittle under strong impacts. So, when 45mm high-hardness T34 plates are attacked by 37mm AP, they resist like about 57mm of medium hardness plate. Against 50mm APC the T34 45mm plates would resist like close to 45mm of medium hardness, while a hit by a German 75mm APCBC round on a 45mm high hardness plate would be resisted by about 34mm equivalent medium hardness. This is why T34 45mm plates are so vulnerable to 75mm hits in CMBB. If the T34 carried 45mm medium hardness plates on the front hull and they were good quality, the 45mm/60 degree glacis would resist like 122mm of vertical plate. And 75L43 hits would bounce beyond 600m or so. But good quality medium hardness plate takes time, care and skilled workers to manufacture, and high hardness allows more tanks to be made with a given workforce.