rexford

Just a note that Dieppe Churchill armor quality was poor, and this was early in war. Shows that British armor was not always good quality. If 88mm armor is poor, what happens with 152mm armor, since thick armor introduces additional burdens and problems compared to 88mm. The above logic doesn't prove anything, but identifies early armor problems which other sources say wasn't resolved till sometime in 1944.

Tiger Fibel penetration ranges appear to be office calculations for 30° hits from target facing, without armor quality or cast armor considerations. Turret front on Mark IV Churchill penetrated at 2000m and 30°, which doesn't seem like a difficult target. Almost 1000m penetration range against driver plate on 30° hits, without armor quality factor. Does CM penalize armor for cast manufacture, which results in different and less resistant structure than rolled armor.

According to Duquette's post, German analysis of Churchill at Dieppe clearly indicates poor quality armor with 88mm thicknesses. What about 152mm thickness at a time that British industry was struggling to produce? We really need actual penetration range figures on true Churchill VII resistance. 95% quality is probably optimistic for Churchill VII, since it appears to be consistent with best quality penetration test plate, and may not represent mass produced tank armor.

The British National Physics Lab equation suggests that as projectile diameter increases 152mm plate resists like less and less. And if the hardness of 152mm plate was 220 Brinell, which is possible, the quality modifier would be alot lower than 0.92 against 88L56 and 75L70. Aren't there any battle reports that suggest penetration ranges for Tiger I and Panther, or 75 and 88 Pak, against Churchill 7 frontal armor? We looked and were not able to find much. This would really be valuable input if anyone has info. Another issue is when during 1944 did British improve quality control, and how many Churchill 7's had already been cranked out? U.S. instituted improvements during October '43 in quality control and heat treatment, until then firing tests passed alot of deficient stuff. We live in USA and had ready access to lots of WW II documents at little cost thru National Technical Information System at State Library in Albany New York. British stuff came from Bovington but was mostly North Africa. We never got to 1944 and 1945 combat from British view. There is also the issue of added armor in contact. Two machineable quality homogeneous plates of 40mm thickness in contact resist like less than 80mm on perpendicular hits. There is alot of add-on homogeneous on Allied tanks, Sherman Jumbo and several British tanks. Super Pershing adds plates over basic Pershing, but spaced plates resist with less gusto than plates in contact. CM treatment of spaced and contact armor may need re-examination.

Thanks for responses.

The intent of the posts was to provide some back-up for 0.95 quality modifier for Churchills and other British tanks. Suggestions based on analysis of armor from different companies in UK, during WW II. Conclusion limited to tank armor. U.S. tank armor industry put out some deficient plates and cast while navy got the alloys and built good thick armor. Tanks and ships had different priorities. I put together the original equations and curves for flaws, which is basis of 0.85 modifier for Shermans and Panther glacis and others. British armor study is just another piece. How valid is it all? Panther glacis and Sherman penetration resistance problems are supported by alot of stories. We don't have much familiarity with actual resistance of British armor to German hits, and put out the posts trying to see what responses we obtained. Comments welcome.

Hunnicutt lists M4A3(75)W ground pressure as 14.3 psi, even higher than mid-production M4A3. Would M4A3(76)W ground pressure be even higher? Panther does not appear to be a particularly boggy type of vehicle, compared to Shermans, using tracks available in France. Of course, analysis is based on Panther scale models. Flotation should be considered, as well as other factors that may apply. To ignore flotation is to miss something important enough to bring to Ike's attention.

My notes indicate that Sherman inadequacies over soft ground may have been addressed in a special report was sent to Gen. Eisenhower on how American armor was comparing to German. Have sent out e-mails attempting to obtain scan of pages to supplement my notes, since my copy is now in Albany City landfill (accidentally placed in garbage years ago). According to note, report included story where Panthers and Tigers completely outclassed Sherman over soft ground, due to narrow Sherman track and gearing (Sherman didn't have proper gear for softground?: isn't clear in notes). "Superior flotation" mentioned in notes. "Duck Bill" track extenders designed to address problem of inadequate soft ground movement by Shermans, and were successful. Eisenhower report also states that Panther 75 had higher rate of fire than 75mm Sherman. "E" report may have also commented on blinding effect of 76mm muzzle blast, and we will look into this. The report prepared for Eisenhower is very thick, and includes numerous cases where panzers fired on and hit Allied armor at 2000m and 2500m. I played Advanced Squad Leader alot when we received the Eisenhower report, and tried to get them to decrease soft ground differences between Shermans, Panthers and Tigers. Ground pressure is normally calculated as weight of tank divided by track area in contact with ground. For Sherman using data in Hunnicutt, average pressure under tracks is 33,350 pounds per track divided by (170" track contact length x 16.56" width), for 13.7 psi for M4A3 mid-production. Measuring from my scale model Panther and treating a metric ton as 2200 pounds, 45,500 total metric tons weight equates to 50,050 pounds divided by (162" contact length x 24" width), for 12.9 psi. So Panther has slightly less ground pressure than M4A3 Sherman if I calculated correctly. Please correct me if I erred, ground pressure is not my specialty and I'am using 1/72 scale models for lengths and widths. Sherman has six wheel locations in contact with ground from front to back. Panther has eight wheel locations in contact with ground from front to back, and there are more wheels per location (better and more uniform flotation). Since tracks have some flexibility, it would seem that more wheel locations and more wheels per location would promote uniform load distribution, and peak load on ground under Panther track could be smaller percentage of total than Sherman, and add to Panther advantage over soft ground. Better flotation could result in faster movement across soft ground.

Another interesting aspect of face-hardened penetration is that penetration falls off as (velocity)raised to 1.25 power, while homogeneous penetration falls off as (velocity) raised to 1.4283 power. Homogeneous penetration more sensitive to velocity, face-hardened more sensitive to projectile diameter. There are some cases where above isn't true, and we believe it may be related to shatter gap failure where T is greater than D, and velocity is over 2000 fps.

Krupp equation for face-hardened penetration: pen=constant x (velocity) raised to 1.25 power x (diameter) raised to 1.25 power x (weight/(diameter)cubed)raised to 0.625 power. Above equation fits U.S. and British face-hardened penetration very well, constant a function of caps and other factors. Note that if 75mm and 57mm APCBC hit face-hardened armor at same velocity and with same (weight/diameter cubed) ratio, penetration for 75mm will be 1.41 times greater than 57mm. Against 240 Brinell Hardness homogeneous armor, 75mm would penetrate 34% more at same velocity and (w/d cubed), so face-hardened penetration is more sensitive to projectile size. We compared homogeneous and face-hardened penetration data for alot of projectiles, with uncapped AP small rounds like 2 pounder penetrate alot less face-hardened than homogeneous, while 152mm AP penetrates more face-hardened than homogeneous. Since face-hardened is more sensitive to impact due to brittle nature of high hardness layer, larger shells do things than 20mm can only dream of. 75mm on Sherman does 91mm of homogeneous at 0m and 0°, does 104mm of face-hardened. Research for our armor penetration booklet looked at all the face-hardened penetration equations and curves, compared equations to published data and identified the equations that made sense. We then estimated face-hardened penetration for ammo and guns that didn't have published data.

During research conducted in dark corners of storage sheds throughout eastern New York State, a U.S. report was found where Shermans were actually less mobile on soft ground than Tigers and Panthers. Report stated that Tigers and Panthers moved over muddy ground that bogged or slowed down Shermans. Results were attributed to narrow Sherman track and deficiencies in transmission gearing. Shermans equipped with track extenders did much better, and came close to matching Tiger/Panther flotation. Ability to move over soft ground more than just ground pressure. Will attempt to contact our special agents and obtain report from secret "FBI" files (Formerly Buried Information).

If British 152mm penetration test plate is 8% less resistant than 1.00 quality (0.92), what about mass produced tank armor?

The British National Physics Lab (NPL)penetration equation was used to predict 17 pounder velocities needed to penetrate 60mm, 76mm, 100mm and 150mm British plate at 0° impact. Results were then compared to DeMarre equation from 60mm, assuming that 60mm had Quality of 1.00. We assumed that all plate had 250 Brinell Hardness, since we do not have access to British hardness-vs-thickness data for later war armor. If anyone has this data and can share it it would be appreciated. A velocity of 1292 fps is needed to defeat 60mm, based on NPL equation. Assume 60mm quality factor is 1.00. Against 76mm plate, 1474 fps is predicted NPL velocity for penetration. DeMarre from 60mm predicts 72.4mm at 1.00 quality, quality factor is 0.95. When 100mm plate was attacked, NPL impact velocity is 1747 fps. DeMarre from 60mm penetration predicts that 1747 fps penetrates 92mm of 1.00 Quality plate, so quality factor is 0.92. When 150mm plate was attacked NPL velocity is 2316 fps. DeMarre from 60mm penetration predicts that 138mm of 1.00 Quality plate should be penetrated at 2316 fps. So 150mm quality is 138/150, or 0.92. CM factor for Churchill armor resistance is close to predictions from NPL/DeMarre equations, and is remarkably close to our finding that 152mm British resisted German penetration like 139mm in tests, which was arrived before we received NPL equation. CM uses 0.95 multiplier for Churchill 7, we would suggest 0.92 for 152mm armor and sliding scale for other British thicknesses (and tanks). Just to be precise in our estimates. And it would be good to use higher German penetration figures as depicted in Diehl's work, just to be in line with the best available info that is out there. With Diehl's permission, of course. A good discussion of NPL equation is contained in Hal Hock's AFV NEWS article, THE PITCHER AND THE STONE, and the British report PENETRATION OF ARMOUR PLATE. As noted in the preceding post, British high hardness armor lost resistance quickly when overmatched (T/d<1) and hit at an angle. Analysis of PzKpfw IVE high hardness armor showed that German armor was 10% more resistant against 2 pounder AP than British machineable armor, and more resistant than British high hardness. NPL equation shows that positive armor hardness effects are more pronounced against small projectiles, and decrease rapidly as ammo diameter increases. We read an account of British high hardness armor, used on light tanks bound for Africa, where residual stresses in the plate caused all of the tanks to split open in the warehouse. When armor is heat treated and hardened, it may shrink as it cools which can produce stresses. Heat treatment should address this. Every country had some problems with armor quality.

During previous research, we obtained a metallurgical analysis of British armor which suggested that the armor did not adequately harden above 2.5" thickness, and would lose resistance. We also analyzed the British NPL (National Physics Laboratory) equation which summarized firing test results as a function of armor thickness, hardness, angle, etc. When German and American high hardness armor was attacked by overmatching rounds (T/D<1), the armor lost some resistance but was still useful. When British high hardness was overmatched, resistance dissolved to almost zero. One of the analyses suggested that 152mm British armor was equivalent to about 139mm of good quality American test plate, based on comparison of penetration data for 75L48 APCBC. Should thick British armor (over 2.5") be penalized a bit more in CM, with greater reductions in quality as the thickness goes up? So actual quality reduction would be a function of thickness and would vary over the different sections of a tank, instead of appying a single modifier for entire tank. We are looking for the source of metallurgical and firing tests, and will provide shortly. Alot of the stuff is in my storage shed somewhere, or is in other people's files (somewhere). On a related topic, Mark Diehl published a series of articles in AFV G2 that included German projectile details and penetration data. This info is published for PzKpfw IV on Will Phelps's PzKpfw IV web site, and Phelps interviewed Mark Diehl during his presentation of Diehl's work. The penetration data provided by Diehl appears to be based on allied tests of German ammo, and exceeds CM figures by a tidy lot. 141mm penetration for 75L48 APCBC at 750 m/s velocity and 0m, about 190mm for 75L70 APCBC at 0m. Diehl's figures for 75mm ammo may be the best figures available for German APC and APCBC, and exceed CM penetration. We looked at the data for 75mm's and it appears to be a DeMarre equation from one gun performance to others, which would be a function of velocity if rounds are 75mm and weigh the same (penetration proportional to velocity raised to 1.4283 power). DeMarre equation works well with U.S. test data in TM-9-1907 and appears to also apply to German ammo. We are not saying that Diehl's data for 88L56 and 88L71 and others is the ultimate, but his 75mm stuff is the best we've seen. We will re-examine the 88 predictions and see how it looks. Finally, why does CM penetration for U.S. 75L40 APCBC exceed TM-9-1907 by so much? TM has 91mm penetration at 0m and 0°, and since so much has been made about U.S. ammo factories and inconsistent quality, how can CM predictions for 75L40 APCBC EXCEED pen. tests using best quality ammo? Inquiring minds want to know.

U.S. penetration data in TM-9-1907 for face-hardened (FH) armor shows some unusual characteristics. Face-hardened armor has very thin layer of brittle, hard steel backed by ductile, non-brittle armor than absorbs impact and supports hard layer. Hard layer is supposed to break projectile nose, even when rounds have armor piercing caps that help to defeat face-hardening. German manufacturing used face-hardening on all front and side hull plates of 30mm to 50mm thickness till mid-1944, which might apply to 30+50 on StuG III, and a large number of panzers with 30mm-50mm on sides. This is a critical issue for wargaming and research because some APCBC rounds can penetrate much more face-hardened armor than homogeneous. Sherman 75 penetrates 91mm homogeneous (same all the way thru and 240 Brinell hardness) at 0m, but 104mm face-hardened. And face-hardened penetration may fall off slower than homogeneous with velocity changes, according to Krupp equation and TM-9-1907. If one uses 75L40 APCBC FH penetration as norm and estimates other rounds from it (using Krupp equation for FH penetration with 75L40 performance as standard): 76 APCBC about 14% low vs. FH 90 APCBC about 14% low vs. FH 57 APCBC about 7% low vs. FH 37 APCBC about 3% low vs. FH (after adjusting for solid shot) When U.S. Navy fired 76mm APCBC against homogeneous armor hardnesses from 250 to 490 Brinell, shatter gap penetration occurred at from 5% to 15% over 50% penetration limit, which is consistent with some of above results. Were armor piercing caps on 57, 76 and 90 APCBC inferior to 75, or was shatter gap playing a role? When one examines the 76mm APCBC FH penetration curve vs. impact velocity, the curve follows 75 APCBC up to 2000 fps impact and then FH penetration falls off like crazy. This 2000 fps limit is where we estimate shatter gap starts to become a potential reality. U.S. Navy tests of 76 APCBC do not show brittle behavior against hard armor above 2000 fps, but they do show shatter gap against hard armor, similar to FH results. To help answer this question and judge its impact in CM, the following points are raised: 1. Can CM provide back-up for brittle American ammo theory that leads to shatters above 2000 fps, reducing penetration. This info would be most helpful. 2. Can CM identify German tanks with face-hardened armor in game.

Here are my parting words on the 75L24 vs 75L70 controversy: 1. our trajectory analysis resulted in a firing elevation less than the descent angle, since the listed elevation angle was not used in the simplified trajectory equation. More exact analysis clearly has firing angle less than descent angle. 2. German manual suggests using twice the testing ground dispersion on battlefield to model combat errors and misaligned sights. This was explained many times in past. 3. An e-mail was sent to Lewis asking for more info on pitch, roll and yaw. When a response was not forthcoming we re-examined our research from 15 years ago and started posting on the subject. 4. Earlier statement on 88L56 was a mistake, turns out that HE from that weapon is accurate even at high velocity due to small dispersion. Mistakes happen, especially when things must be explained over and over again, and then again and again, and .... 5. Trajectory analysis shows that 75L24 HE is more accurate than 75L70 given equal dispersion, or even when 75L24 dispersion is twice L70. 75L48 HE dispersion used because it was only 75mm HE data with dispersion, as was explained in earlier post (see previous comment on continuous explanations). 6. We found Diehl's original work on German 75mm HE. 75mm guns except Panther 75mm fired HE with 0.853 kg bursting charge of 60/40 Amadol. Panther 75 HE had 0.654 kg of 60/40 Amadol, so 75L24 HE had 30% more bursting explosive than 75L70, which supports concept that high muzzle velocity is associated with a decrease in weight of explosive. 7. Phelps' web site on PzKpf IV appears to present correct info on 75mm HE shells, comparing info on that site to Diehl article. 8. 75L24 HE trajectory is more accurate than Panther 75 HE against ground point targets, 75L24 HE contains more HE than 75L70 HE and 75L24 also fires cannister. with 960 9mm steel balls in each round. 9. We have German ballistic data on just about every APC, APCBC and HE round used during WW II, in original German and interpreted by a group of people we know.

Lewis, In both of my trajectory analyse's the descent angle is greater than the firing angle. See bottom of page 7. Please read both analyse's. Though the give and take has really been beneficial, and we were forced to dig up info that was out of sight and mind for years, we're moving on. This has gotten too booring, too repetitive and your comments are too often baseless. You can accuse me of whatever but we're (me and you trading posts) finished on the 75L24-versus-75L70 HE thread. You can continue if you wish. And I never opened a post from you after asking for more info. Your posted comment on pitch, roll and yaw reminded me of previous work we did over 15 years ago, and we went back to it and used OUR PREVIOUS RESEARCH to analyze first shot impacts when gun is firing across an angle. We have been at this for almost 30 years, and have looked at most things.

Double actual dispersion is normally used on first shot attempts to include errors that occur on the battlefield, as well as weapons that go out of adjustment. 0.45m on testing ground is 0.9m for first shot on battlefield and was rounded to 1.0m for convenience. 75L24 vs 75L70 HE analysis would yield same relative result regardless of the dispersion value that was used.

I now have Diehl's original article on 75mm HE, found in my storage shed. Following rounds have 0.853 kg of 60/40 Amadol bursting charge in HE: KwK 37 StuK 37 KwK 40 StuK 40 Pak 40 Following round has 0.654 kg of 60/40 Amadol in HE: Panther KwK 42 So 75L24 HE is not only more accurate than Panther HE against ground point targets, but short 75 contains more bursting charge. Since 75L48 HE is similar to 75L24 in muzzle velocity (an opinion that is seconded by my honorable adversary), it is no wonder that 75L24 and 75L48 HE have the same bursting charge. Diehl's data supports Will Phelps' PzKpfw IV site, and the possibility of a typo on Mr. Phelps' site regarding 75mm HE has now been resolved in his favor. My recent posts regarding effect of cant were researched over 15 years ago, and have not benefited from anyone's assistance in the last year, though help was requested in a direct e-mail which appears to have gone unanswered.

Lewis, Maybe your reading isn't getting it. Do you have any substantive response to offer regarding the trajectory analysis on Page 7 that shows that 75L24 HE is better at placing rounds near the target point than 75L70 HE? I presented a mathematical analysis with all the things you continously and non-stop asked for, descent angles, dispersion, flight times, etc., and you didn't say one word about the work. Just switched to another issue to hammer on. Soldiers over an area are still a ground point target because the round is aimed at one point. See previous posts for definitions ad nauseum.

My explanation of dispersion agrees 100% with Ridgeway post. Dispersion is measured about mean impact point, which is the mean trajectory height. The 'Natter Gap thread is 100,000 times more interesting than this unending and unfruitful attempt to communicate, and my wife found the 'Natter Gap posts funny, too. The little yellow moving objects shocked her a bit, though, which was good to see.

Lewis, A ground point target is fired at by aiming at a specific point on the ground. Ten men spread over an area requires the gun to aim at a specific ground point. This is so simple. One aims at a single point. Has to aim somewhere. And my trajectory dispersion definition is correct. My previous analysis showed that 75L70 HE will spread over a greater area than 75L24 HE, so if a squad covers a specific area and fire is aimed at middle of group, 75L24 HE has greater chance to land HE close enough to "area" to impact squad. But an "area" target is still a ground point target because the gun is aiming at a single point on the ground. Awaiting your ballistic analysis. Presented mine and noticed that no substantive comments were made. In fact, no response at all to the math. On another matter, 88L56 HE fired at 810 m/s but vertical dispersion very small, so beaten zone not as large as velocity would imply. I have now repeated the definition of ground point target at least 20 times, and it appears that you still don't understand how I am using the term. Please reread my previous posts and instead of attacking the explanation, try to let it sink in.

I believe my last post pointed out that Soviet penetration ranges in Jentz suggest that the Tiger II that was tested had good quality armor. So I changed a previous statement in an earliet post to say that Tiger II's may have been like Panther glacis, some good, some bad. I agree with the recent posts, make a random computer dice roll where quality ranges from good to high severity flaws. We do this. Most Shermans were bad, maybe 70% to 50% of Panthers if one is willing to use a six Panther firing test sample as the universe. In the absence of anything else, we use it because there is nothing else. Or one can model bad armor using the bell-shaped curve that CM uses so much. Alot of tanks near 1.00 quality, alot below 0.90 quality, some below 0.85 quality. Every Panther was not bad, and the rest of the Panther armor does not appear to have been bad often enough to warrant a quality decrease. Shermans are another matter. Some were good quality, but most were bad. American engineers talking to Russian engineers said they had bad armor, which may suggest that it was bad front, side and rear.

We have now revised our views on shatter gap after looking at Shoeburyness tests. 75mm APCBC did not shatter fail when penetration exceeded resistance by more than 5%. It appears that impact velocity must be at least 2000 fps for rounds to break up, armor thickness must be close to, equal to or greater than projectile diameter, and penetration must exceed resistance by more than 5%.

Lewis, Your comments about my posts have already been responded to. 1. Vertical dispersion is applied about the mean trajectory calculated using just gravity and initial elevation angle. If the mean trajectory height is 1m above the ground and 50% of the dispersion will be within 0.5m, then 50% of the shots will be between 0.5m and 1.5m above the ground. My friends speak fluent German, some of their fathers were test pilots and the like during the war, and everything on the German ballistic tables has been thoroughly translated and made sense of. 2. Ground point targets occur when a target is a point on the ground, which occurs in the example you referred to. 3. The superiority of 75L24 HE over 75L70 HE is based on the attempt to drop an HE near the middle of a point target on the ground. Would ricochet fire always be used instead of aimed fire at point targets? No. Terrain between target and gun may be rough. Looked at another way, if 75L24 HE lands closer to point that is aimed at, ricochet fire with 75L24 might be more accurate than 75L70 HE. 4. We are really thankful for some of the info you have provided. 5. Unless you back-up your assertions with analysis, and stop playing games with "how do you define dispersion and then I'll correct you", your posts lack any validity and appear to be nothing more than attempts to discredit our posts by creating doubt. Back up your assertions with some hard math, like we did. If you cannot understand what a "ground point target" is, then further discussion is useless. Bye.