rexford

Thanks for responses. The close similarity of 75 and 105 seemed interesting. Probability of landing a round within 20' of someone is small. Next question: anyone have data on fuze delay times for HE other than Sherman 75mm. If faster HE rounds had shorter fuze delays on ricochet fire this would affect calculations. Good point about using max HE filler weights, Russian ammo also presents a host of different weights and it is difficult to figure out which one is most common. Will have to ask fellow who published those figures about which was most common. Once again, thanks so much for the responses. We're putting finishing touches on our armor booklet and all help is appreciated.

The Shermans with the 47 degree glacis had some real weak frontal areas, like 89mm mantlet and 2" cast nose armor at 56 degrees that lost 15% of its resistance when it was hit by 75mm rounds. But the interesting thing is that the glacis provided more resistance than the Tiger E driver plate, and about the same as the Tiger nose. 2.5" rolled armor at 47 degrees resists 75mm APCBC hits like 116mm at vertical, as opposed to the Tiger driver plate 102mm at 10 degrees for 105mm. 10% more resistance on 47 degree Sherman glacis, about same as 102mm at 25 degrees slope. Pretty good, and no flaws in most 47 degree glacis tanks. Too bad all the frontal hits don't land on the 47 degree glacis armor. 56 degree glacis Shermans with flaws might present about 95mm at vertical to 75mm hits. Big difference. PzKpfw IVH tankers noted that their 75L48 gun couldn't penetrate 47 degree glacis at 1000m. Further research on HE effectiveness adds to previous finding that US 75mm HE put out sa larger number of effective fragments than 76mm and 90mm HE at all meaningful ranges, and 94% of 105mm HE figure at 20' from blast. 75mm had very high percentage of total weight as HE filler and probably had thin walls, so more high velocity fragments, though they were small and lost velocity fast as suggested by data. So 75mm HE is close to 105mm at 20' in terms of effective fragments but only has half as many as 105mm at 200': data suggests that 105mm puts out larger pieces that lose velocity slower Ricochet fire with 75mm HE has a 0.05 second delay between hitting ground and exploding, so US Army firing manual says round has to land within 20 to 25 yards in front of target to be effective with ricochet fire. As discussed in previous threads, low velocity guns appear to be more accurate than higher velocity in terms of placing HE on or near a ground point, since flatter trajectory will have greater scatter in horizontal direction due to vertical dispersion. So, not only does 75mm have more HE punch than 76mm and 90mm, but low velocity 75mm HE appears to better at ricochet fire due to less horizontal scatter. The accuracy issue discussed above continues to support the need for two separate accuracies for HE fire, one based on ground target aim and another based on the ability to hit vertical targets. Low velocity better at hitting specific ground points, high velocity better at placing rounds throught bunker openings and hitting things like walls, buildings and vehicles. German 75mm HE from PzKpfw IVH weighs 12% less than US 75mm HE shell, and has slightly heavier HE filler. US 75mm uses TNT according to British data on John Salt site, while German 75mm HE uses 60/40 Amadol (what is this stuff?). Is Amadol equivalent to US 75mm HE filler in terms of effectiveness? Some British HE uses 60/40 Amadol, again from John Salt site. Panther 75mm HE has less amadol than 75L48 HE, which is consistent with higher velocity HE having less filler and possibly thicker walls. The data on German HE comes from Mark Diehl article in AFV-G2, American fragment info from TM9-1907. Conclusions are mine. Would appreciate reader input on Amadol vs US HE filler, and anything else that comes to mind after reading through the above conclusions. I'am flexible and open to rational and factual input.

Is chronology a factor in why one test shows poor APDS quality and another doesn't? In other words, did APDS get better with age? APDS problems appear to be based on alot of gun related problems and some basic manufacturing problems. So three questions arise: 1. were solvable APDS problems identified and addressed prior to war end? Could be yes or no, but no real statements were found that significant improvements transpired before war's end. Anyone with info on this invited to participate. 2. is it possible to identify a date when APDS improved, and the percentage of available rounds that benefited, for wargame purposes (probably not) 3. would be it be reasonable to use the same factor for random APDS inconsistency throughout the war (probably) March, 1945 6 pdr APDS tests are addressed in Jentz book, and results suggest a good percentage of bad ammo. Yes, we have no dates for the two tests, so our findings are suggestive rather than definite. And there is a 50% chance that APDS-better-than APCBC test occurred earlier than the other test. APDS is inconsistent on about half the shots, and there is no data as to when any improvements took place during WW II, if any. If anyone wants to search through WO reports for dates and details, and then search for APDS improvements during WW II and associated details, it would be appreciated.

Bump!

Prior to posting the data on the second test (APDS-vs-APCBC accuracy), we looked at the factors that might vary between tests, and realized it was manufacturing differences. As a licensed professional engineer with mucho experience doing statistical studies and sampling, as well as quality control, it was obvious that many factors canceled out and lot quality was the primary factor. With regard to Simon Fox' intriguing and startling findings on why the two tests on John Salt site pointed to basic inconsistencies in APDS manufacturing, they aren't. We figured out a long time ago one test had a good lot, another a bad lot. We've been saying inconsistency was a basic element of APDS accuracy and penetration for a long time.

With regard to the preceding post, 75mm M48 HE shell is about 11.5% HE filler, same as 90mm HE. But 90mm HE may have relatively thicker walls, so more resistance to explosion, leading to fewer and larger fragments with less velocity. The above explanation would be consistent with TM data that predicts more 75mm pieces with high velocity at close range. The larger size of 90mm fragments would hold velocity better than 75mm, resulting in smaller differences between the two (effective fragments) as range increases. This is what happens with TM data. The above explanation seems to explain the TM-9-1907 data and brings up some issues that may not be considered in the John Salt data. Input would be appreciated. Thanks.

The one point about the British analysis of HE equivalency to 25 pdr HE is that it seems to be based on amount of metal and HE filler. If one looks at the percentage of total shell weight that is HE filler, and considers shell wall thickness (thinner at lower velocities) then it is possible that 75mm HE was comparable to 90mm HE, slightly less effective than 105mm HE close to the blast and alot more effective than 76mm HE than most rulesets predict. In other words, the U.S. fragment analysis in TM-9-1907 may be justified on the basis of factors that were not considered by the British.

Simon Fox: Long before your last post, we looked at the two APDS-vs-APCBC accuracy trials with different results, examined the causes of APDS variation that would be common to both tests, considered an estimate of total rounds fired, and realized that different lots were probably involved : one lot was good, one was bad. The above explanation is essentially the same as the bureaucratic and "clear as mud" concepts you just espoused. Since production inconsistencies were likely to be the main difference between the two tests, it backed up our theory that APDS was, as a general rule, inconsistent. Conall's response's on APDS have suggested that quality control and production quality could vary, representing a primary difference in two test results. By the way, I'am a licensed professional engineer and have done ALOT of work on statistical sampling, quality control and confidence intervals relating to airport pavement condition studies. Regarding your startling analysis of APDS inconsistency between two tests, it isn't.

Simon Fox: You made a comment regarding my interpreting John Salt for the masses and I responded by using another thread as an example. Sorry if small changes in course confuse you.

The interesting thing about the John Salt HE data is that it supports the CM HE ratings, with 90mm and 105mm HE given a larger 25 pdr HE equivalency than 75mm HE. Although 90mm HE does not appear to be appreciably larger than 75mm HE. U.S. data in TM-9-1907 suggested that 75mm HE effectiveness was closer to 105mm and 90mm HE, which may not be reasonable. So the John Salt data helps to put TM-9-1907 in perspective. My comment about CM missing 75mm superiority over 76mm HE was an error. The British estimates for effective blast area were based on total weight of HE round that hit ground, so may not have considered weight of HE filler which would increase 75mm HE advantage.

My interpretation of Salt' snippets is made in the context of other information on APDS performance, so that the entire picture can be seen. The benefit of my work is that the snippets can be better understood after other test data is reviewed and taken into consideration. My interpretation of snippets can be summarized as follows: sometimes APDS is less accurate than APCBC, sometimes it is more accurate. Can't argue with that assessment. Isigny report indicates that sometimes APDS penetrates Panther glacis, sometimes it doesn't. So APDS is inconsistent, and all the test data supports that assessment. I would be glad to review a Simon Fox analysis that concludes something different.

Simon Fox: The point of APDS-vs-APCBC firing trials is that APDS is inconsistent, it may be less accurate than APCBC in one set of tests and then perform better in another test. This has been the point of all the information posted on the subject, APDS cannot be modeled with one set of accuracy or penetration stats because it is all over the place. Sometimes it works well, sometimes it doesn't. No contradiction here. The test data I referenced is firing test data, not calculated or estimated.

John Salt site ending in salt5 has comparative accuracy tests where 6 and 17 pounder fired APCBC and APDS (WO 291/324). 6 pdr APDS is less accurate than APCBC, 17 pdr APDS is more accurate. This continues the APDS story of inconsistent behavior. It is also notable that APDS accuracy is not improved by zeroing gun to APDS performance as opposed to APCBC, as British had theorized.

John Salt site ending in salt5 has data on panzerfaust accuarcy at various ranges, which might be helpful and of interest.

Same site states that 75mm M48 HE is longer, heavier and has greater capacity than 76mm M42A1 HE. This supports earlier thread I started some time ago using TM-9-1907. And it shows that 75mm HE outclassed 76mm HE in every way, including total scrapnel weight. Those John Salt snippets are very good.

Salt5 has some very good British analyses of relative HE effectiveness, see WO 291/955. U.S. 75mm HE is shown to be more effective than 76mm HE on the basis of total shell weight and HE filler. CM missed this, it would seem, if British stats are correct. 75mm M48 weighs 14.6 lbs and has 1.7 lbs of explosive, 76mm M42A1 weighs 12.9 lbs with 0.9 lbs HE. 76mm puts out less scrapnel at lower speeds, so is less lethal than 75mm HE. Following is conversion of various HE shells to equivalent 25 pdr HE weight: 75mm 25 lbs 76mm 20 90mm 30 105mm 40 6 pdr 10 17 pdr 20 25 pdr 25 95mm 35 3.7" how 25 This data is slightly different than U.S. figures from TM-9-1907 but looks authoritative and gives HE shell weight and HE filler lbs for a large number of rounds. Nice looking info. Another bit of info on same site gives 2900 square feet for 75mm HE imnpact area, 2200 square feet for 76mm.

John Salt is the ONLY site where correct APDS slope multipliers can be found, something I have been pointing CM to for some time. Look on bottom of penetration page. Our booklet makes much use of data from Salt site. Salt site is only source for tungsten ammo penetration of face-hardened armor, and provides the best compilations of penetration data anywhere. Plus lots of British WO reports on penetration and hit probability. When our booklet comes out readers will see how valuable the site is, references to salt abound.

The last part of the John Salt address should read salt6, not slat6. Sorry.

Simon Fox: Please advise where valuable regimental histories can be found to illustrate the points you made (former and latter comments). There aren't too many at local library.

Simon Fox: Please provide a bit more to support your response. You don't think the test results are valuable with regard to illustration of various factors, including difference between good and bad. If people can't shoot well in a test, what happens with some pressure? And if APDS doesn't do well in a test, why should it be better in combat. More and more evidence pointing how out inconsistent and inaccurate APDS was AT ALL RANGES. I don't see where diaries make that much difference when we're examining firing tests.

The APCBC/APDS comparison in my first post on 6 pdr firing tests compared 5 tank APCBC to 3 tank APDS (best 3 against best 3 plus worst 2). Following is comparison of best 3 tanks for each ammo, % refers to overall hit percentage against 2' x 5' target (Panther turret): 500 yards 89% APCBC, 74% APDS 800 yards 84% APCBC, 50% APDS 1000 yards 81% APCBC, 37% APDS 1500 yards 62% APCBC, 20% APDS APCBC is much more accurate than APDS for best 3 tanks.

http://www.britwar.co.uk/salts/slat6.htm contains firing test results for various British guns and ammo. WO 291/762 at bottom of page has a test with Churchill 6 pounder against 2' x 5' hulldown turret model. Interesting thing is that two tanks out of five are so poor in their shooting that they are left out of comparisons between APCBC and APDS. How much poorer, you ask: 500 yards 89% accuracy for better 3 shooters, 52% for worst 2 800 yards 84% for better 3, 57% for poor 2 1000 yards 81% for better 3, 34% for 2 bad shooters 1500 yards 62% for best 3, 24% for 2 worst Percentages are for all shots taken at target, which includes follow-up to first try. Shows that better gunners zero in on target, even a turret, after a while and obtain high overall hit %. At 500 yards the least accurate 2 can only muster 52% accuracy after several shots at target? The above stats give a good idea of the difference between good gunnery and a possible combination of less than able hands, eyes, concentration or bad guns/ammo. 6 pounder gun in Churchill had elevation changed by gunner lifting or lowering a yoke on his shoulders? This might have contributed to some degree. If CM had been modeled on these test results we would see many more hits and a wider variation between aces and sad sacks. Yeah, they are only test results without the pressure of someone firing back, but the great variation between good and bad is likely to carry over to the real thing. In a recent CM game, a Tiger took alot (I mean a steady 2 or 3 turns worth) of HE shots at a running infantry squad inside 100m range, and didn't pin or kill them. Many shots just changed the direction they were running. ?????

During the firing tests described in previous post, it was found that two Churchills had such awful accuracy with 6 pounder they could not be included in overall statistics for comparing APDS with APCBC. This suggests a new thread.

British report WO 291/762 describes the result of a comparative firing test with 6 pounder APCBC and APDS against a 2' x 5' target (hulldown Panther). Churchill IV was used. See the John Salt site on hit probability. APCBC outperformed APDS beyond 500 yards in terms of hit %: 500 yards, 74% for both ammo types 800 yards, 50% for DS, 73% for APCBC 1000 yards, 37% for DS, 62% for APCBC 1500 yards, 20% for DS, 42% for APCBC British found that dispersion and jump varied so much from one gun to another during APDS use that a single conversion factor did not apply to all tanks when they used the APCBC gun sight settings (with 17 pounder, multiply estimated range by 0.5 when firing APDS and using APCBC gun sight scale). If individual gun characteristics were used to construct range conversions with APCBC gun sight settings, APDS accuracy might be improved by about 60%. Despite probable absence of muzzle brake on Churchill IV, APDS was still less accurate than APCBC. John Salt site also provides report that recommends 800 yard max range for APDS, based on 50% first shot accuracy against hulldown tanks. In difficult situations, such as when facing a Tiger II at 1200m with no where to run or hide, 17 pounder armed tanks might resort to APDS in the hope that they had decent ammo, since APDS might penetrate the turret front and APCBC definitely would not. So APDS performance is inconsistent during 6 pounder trials despite probable absence of muzzle brake, and accuracy is less than APCBC at ranges below 1000m. This points to problems may that go beyond muzzle brakes and involve petal shed/exhaust gas interference. APDS accuracy is, as has been theorized, a truly random event that requires random selection of accuracy and penetration figures. Listening CM?

APDS penetration and accuracy could also dramatically decrease from 200 to 800 yards, as indicated during the Isigny tests.