rexford
-
Posts
1,567 -
Joined
-
Last visited
Never
Posts posted by rexford
-
-
We're currently looking into some data that may significantly reduce PzKpfw IVH frontal armor resistance against allied APCBC projectiles, so we're not looking for German advantages. Just trying to get fair depictions of armor that wasn't bad all the time (Panther glacis), or wasn't bad too often (rest of Panther).
If we wanted to skew the game how about "shatter gap", where 76mm APCBC breaks up against Tiger 100mm near-vertical plate from 300m thru 1000m. CM doesn't have this and should, in our opinion.
Our rules have shatter gap, and U.S. 76 has no teeth against thick armor until HVAP.
In Faint Praise reports, 76mm U.S. couldn't do squat against front of Tiger beyond 50 yards.
We have a long list of things that CM would have to do to match our rules, but don't expect the world to change to match our vision. Wargame design and research is an art and what suits Picasso would irritate Renoir, and vice versa.
Panzer IV web site from Will Phelps presents German penetration data based on U.S. tests that exceeds CM figures by enough to give Germans added advantages. It even exceeds our figures.
Is that pro-German uber-tank enough?
-
Oops! Made a mistake. 75L24 HE fired at 420 m/s.
Sent in post after dental appointment and misread sheet.
-
122 reliably penetrated Panther glacis in tests, 88L71 and 100mm penetrated to a certain range.
Soviets doing penetration tests were smart, and like British they probably ruled out hits within a given distance of edges and weak points like MG port. Give the tester some credit.
Good quality resists like it should based on slope effects and penetration data, bad quality cracks after defeating hits or is penetrated easier than it should be.
Metallurgical results are impossible to obtain for tested tanks, but we can still use test results to draw conclusions based on how armor reacts. Real world analysis.
In real world data is incomplete and results may be all that is available. If one Panther glacis cracks wide open at 200 yards, and another resists hits without any failure or major damage at same range, quality is inconsistent.
0.85 is comparison of penetration resistance with medium flaws to what would be expected of good quality armor. U.S. did tests on 1940 armor plate, and correlated results with sonar grams of some sort that showed size and extent of flaws like laminations and inclusion.
We analyzed penetration resistance vs. flaw size and extent and have curves that relate penetration resistance as % of good quality armor. Good quality armor had no flaws in tests, was fully ductile and resisted in a consistent way.
For armor wargaming purposes, it is not necessary to define metallurgical qualities of armor plate, it has low, medium or high severity flaws at a given % of cases. We are not going to hold up our booklet looking for data that is impossible to obtain.
Alot of assumptions but it presents the results of alot of mathematical analysis and is the best that is available. CM is based on our work, with some variations.
If someone wants additional details on how we determined our results or put together a conclusion, ask. If you question someting I say ask for supporting data or an explanation.
We have spent close to 30 years on the armor penetration booklet, can explain everything we say in detail or in summary fashion, and are open to new data and changes. Initial statements are usually general and leave out alot of details, if you want more ask.
There are many engineering areas where it is impossible to mathematically predict what is going to happen due to too many factors. Soil mechanics can be like this.
So general results are correlated with a few factors and equations or procedures are proposed that catch the main drift of what is likely to occur. But people using the math realize that what actually occurs may vary.
Panther glacis armor and Tiger II's don't resist hits in a consistent fashion, and we have tried to model this using 1940 American tests on flaws. We had to use something and the results seem realistic, that is all one can look for.
-
John,
We have actual American test data for 122mm against U.S. armor plate, penetration ranges in Potapov have been compared to our data and they are reasonably consistent in every case.
Jentz book has Soviet test results for a long line of guns and ammo against Tiger II. These results have been compared to our data predictions and good quality armor is suggested.
So Tiger II armor may be like Panther glacis, quality varies from tank to tank. But Panther glacis is only part of tank that exhibits poor quality, entire Tiger II appears to be poor quality alot of time.
When our booklet comes out you can calculate the estimated penetration ranges for Soviet ammo and you'll see that it matches up well with stories and tests we quote.
We were able to estimate penetration for other Soviet guns from U.S. test of 122.
We don't accept every Russian penetration range report or quote as godsend, we compare to our data and other material and see if it is reasonable. In most cases it is good stuff.
-
Panther glacis armor should be modeled with some sort of variable quality factor.
Isigny, France
August 1944
1 of 3 Panther glacis is good quality, other 2 crack after 17 pounder APCBC hits defeated at close range.
Kubinka, Russia
Late 1943
Panther glacis attacked by 88L71 and 100mm Russian gun resists penetration like good quality armor. 88L71 penetration limited to 650m, 100mm to 1450m.
122mm easily and reliably penetrates glacis at 2500m, which suggests less than 100% resistance.
Above two tests suggest that half of Panthers have good armor, half poor. Six Panthers out of thousands is not a statistically valid sample to draw wide conclusions. But some Panthers definitely were close to good quality, so a game that penalizes all Panthers is not really being fair.
Potapov site states that Panther armor deteriorated quickly starting late 1944, due to German loss of alloy mines in Russia. Tiger II's captured by Russian has consistently bad armor on all areas, although side is worse. Panthers met in France during 1944 probably would include alot of good armor vehicles.
To repeat another problem with CM, only the glacis was consistently flawed in allied and Russian tests, we have never seen any evidence that the rest of the Panther had problems. The Panther nose and mantlet perform as good quality in every report and test we have ever seen.
Our group invented the curves for flaw effect as a function of T/D, and our work probably is the basis for armor quality in CM. When we apply flaws in our games, only the Panther glacis has flaws on a regular basis, and the quality varies.
Panther cast mantlet armor was not flawed because it was on the Panther, if Panther mantlets came from the same factory as Tiger cast mantlets one would have to explain why one is bad, one is good.
Panther glacis armor shows a high percentage of flaws in our study, the rest of the Panther seems okay and that is why we feel that the 0.85 multiplier should only apply to the mantlet, and then on a random basis.
A computer dice roll for each hit would be fair, although the entire glacis would probably be bad if manufacturing resulted in problems. Not letting anyone know if a tank had bad armor on the glacis would be ideal.
Panther glacis armor is listed as 85mm thick in many Russian, British and American documents, and penetration ranges at Kubinka suggest 85mm Panther glacis. 80mm may have been the design thickness but 85mm may have been the actual in many cases.
Sherman armor prior to 10/43, on the other hand, was consistently poor with a small percentage of decent armor.
-
In my last post, one correction:
Panther HE descent angle at 400m will still be smaller than PzKpfw IIIN 75L24 HE.
-
1m vertical dispersion at 800m for 50% of 75L48 HE is doppelte streung dispersion. Actual vertical dispersion at 800m is 0.45m above aim center and 0.45m below, double dispersion used in analysis is 1.0m above or below.
This data is based on actual German firing tests conducted at a few ranges between 0m and 3000m, with a curve drawn between the data points.
It is real data taken from a German ballistic table, we have these tables for APC, APCBC, HEAT and HE rounds.
The overriding point is that if the vertical dispersion for L24 and L70 German 75mm HE was 0.3m, the L24 still is more accurate than L70 in terms of landing rounds close enough to cause losses. The analyse's at the bottom of page 7 in this thread show this conclusively, and since those studies used 450 m/s for L24 HE and it could be as low as 385 m/s, advantage over L70 HE is even greater.
Vertical dispersion at 400m would be about half of 800m figure, although descent angles would also be about half, so beaten zone at 400m would be slightly smaller than 800m.
Panther HE takes 0.6 seconds to 400m, PzKpfw IIIN 75 HE takes 1.1 seconds, so IIIN HE trajectory will still be curvier. Panther 75 HE descent angle at 400m is still going to be larger than PzKpfw IIIN HE at 400m, difference between the two will be smaller than at 800m.
-
Allied firing tests suggest that only the Panther glacis had deficient resistance, the rest of the tank was okay. The Panther cast mantlet came from different processes than glacis, and since Tiger cast mantlet is generally held to be good stuff Panther mantlet should also be.
Panther cast mantlet performed well in Allied tests and held U.S. 76 to 200 yard penetration range in Normandy, based on Faint Praise reports.
I work with Robert Livingston, and we're putting a booklet together on armor penetration that will present consistent penetration and armor data, everything to same basis.
We have made CM suggestions along the way, maybe they got lost in the verbal forests.
CM figure for resistance deficiency of Panther glacis (85%) is medium flaws, many tanks had no flaws, some had high severity flaws. We roll dice in secret.
-
In response to John Waters' post, where French trying to hit a vertical or horizontal target.
Earlier analysis based on a ground point target, say tank is trying to drop HE in them middle of a group of soldiers at 800. 75L24 more accurate than 75L70 on this due to curved trajectory of short 75.
Maybe French were firing Panther HE at a vertical target, such as a building or tank, and 700 m/s HE round might hit on 3rd or 4th shot with bracketting.
My earlier posts repeatedly noted that the normal "To Hit" accuracies don't count for HE fire at ground point targets, since slower is actually better if ground is fairly level. Two HE accuracies would be the ultimate, one for ground point targets and one for vertical targets.
75L24 is bad at hitting vertical targets accurately on the fly, but is good at consistently dropping HE close to a target.
If infantry at 800m are on the side of a small hill facing a tank, it might count as a vertical target or ground point target, depending on alot of factors.
Previous posts are based on the distinction between vertical HE targets and ground point HE targets.
-
Received an e-mail that CM accuracy at 2000m is higher than 4.5% for many guns, and follow-up shot accuracy may reach 3 times the initial figure after repeated shots at the same target.
Please note this correction to my earlier e-mail.
-
Will Phelps' PzKpfw IV site losts two muzzle velocities for 75L24 HE, 385 and 420 m/s.
1.0m vertical dispersion for 50% of shots is from German ballistic tables, as I mentioned previously. A careful re-reading of the accuracy analysis will verify this. This is figure for 75L48 HE at 550 m/s.
75L24 HE at 385 m/s would have significantly different trajectory and accuracy from 75L48 HE at 550 m/s.
Never said German HE was superior to Sherman 75mm HE, only that 75L24 HE had heavier explosive weight.
Finally, interesting to note that none of the complainers about absence of trajectory analysis for 75L24 HE accuracy has commented on the Page 7 study that supported our theory.
-
75L24 HE was actually fired at 385 m/s and 420 m/s, so the advantages over 75L70 HE noted in my previous studies would be increased.
Previous studies used 450 m/s.
-
Where is patch that changes HVAP and APDS slope effects? Asking in a nice way.
I may have missed where to get all the changes.
Thanks.
-
Did a more accurate trajectory analysis.
Ground point target at 800m, range estimate is 800m. 75L24 HE fired at 450 m/s, 75L70 HE fired at 700 m/s.
75L24 HE trajectory has firing angle of 1.281° and final descent angle of about 1.429°. 1.905 seconds to 800m.
75L70 HE trajectory has firing angle of 0.507° and final descent angle of about 0.564°. 1.200 seconds to 800m.
If vertical dispersion is 1.0m, 75L24 is off by 40m and 75L70 is off by 102m on flat ground. Higher percentage of 75L24 HE shots land close enough to target to do something useful.
What happens when 88L56 tries to hit a ground point target with 810 m/s HE? Would you rather have 75L24 or 88L56 against a ground point target?
-
The simplified trajectory equations are based on rounds over 2000 fps, so offer rough estimates for slow stuff like 75L24.
Will do more exact analysis in next hour and post it.
-
75L70 fired HE at 750 m/s, 75L24 HE at 450 m/s.
75L70 HE took 1.2 seconds to reach 800m with 10 mil gun elevation, or 0.573° gun rise.
This is from German ballistic data that we have.
75L24 (estimated from 75L48 HE ballistic data starting with 450 m/s at 1075m and going to 390 m/s at 1875m) takes about 1.905 seconds to go 800m.
Using our simplified trajectory equations, descent angles at 800m are 9.49 mils for 75L70 HE and 23.0 mils for 75L24. In terms of degrees this equates to 0.544° for 75L70 and 1.318° for 75L24.
If dispersion drives trajectory up by 1m at 800m (German data shows that 50% of 75mm L48 HE shots will have vertical dispersion of at least 1m at 800):
75L70 HE is off by 105m on shot at 800m when range estimate is perfect and vertical dispersion is 1m
75L24 HE is off by 43m on same shot as 75L70 HE.
How many HE shots will be within 20m of target when range estimate is perfect and 50% of vertical dispersion exceeds 1m?
--------------------------------------------
10% of 75L70 HE shots will be within 20m of target with a perfect range estimate at 800m.
24% of 75L24 HE shots will be within 20m of target with a perfect range estimate at 800m.
--------------------------------------------
There it is, trajectory analysis that fully supports what my posts have been saying, 75L24 HE is very accurate due to low velocity and arching trajectory, and "if" 75L24 HE round has more explosive then other German ammo (and I am getting the Diehl pages on this), then 75L24 is even more lethal.
-
We looked into what Gaussian bell shaped accuracy curve means, and how it stacks up against other analysis.
Assume 4.5% accuracy at 2000m on first shot for 88L71 APCBC, target is stationary and in full sight.
So 2000m equals about 2.00 standard deviations, 1 standard deviation is approximately 1000m.
92% at 100m
80% at 250m
62% at 500m
32% at 1000m
13% at 1500m
4.5% at 2000m
62% accuracy at 500m seems low for 88L71 APCBC, and may account for all the misses we have been seeing. With average 25% range estimation error (individual errors follow a bell-shaped curve and vary from 0% to over 75%),the hit probability may be closer to 90% to 95% at 500m for 88L71.
5% at 5000m
If 88L71 attains 43% "eighth shot" accuracy at 2000m after closing the range with bracketing, standard deviation is 2532m, so:
97% at 100m
92% at 250m
84% at 500m
69% at 1000m
55% at 1500m
43% at 2000m
32% at 2500m
23% at 3000m
17% at 3500m
11% at 4000m
The above results seem okay for wargaming, we would hold max hit % on any shot to 90% for realism sake (no one is free from mistakes and silly blunders all the time).
84% at 500m will allow for alot of factors that cause theoretical rate of fire and individual shot accuracy to lag behind training field exercises (hard to find or lift ammo reserves, jammed guns or fingers, confusing commands, sweat in eyes, etc.).
If max accuracy at 2000m against a stationary fully exposed target is 10% after eight shots, this seems a bit too conservative.
-
Lewis,
1. If I read an article 10 years ago would I have been able to give the HE weights to two or three decimal places. If you read thru all my recent posts it is obvious that we reread Diehl in reponse to your question.
2. Right now, Phelps' site may contain a typo regarding HE used by German 75mm guns, and we are looking to see if that is the case. Our reading of Diehl is that 75L24 packed more explosives than 75L70. We have the original Diehl articles, Phelps uses Diehl if you would read his references. Typo's sometimes occur when data is transferred.
3. Our comparisons have been between 75L70 and 75L24 HE, where there is a major difference in velocity. Your statement that 75L40, 75L48 and 75L24 HE is not that different in velocity, and we are therefore way off base, is just another attempt to cloud the issue.
We said that 75L24 was very accurate against ground point targets and had more HE explosive than 75L70, and 75L40 HE was more accurate than U.S. 76mm HE and had more explosives.
4. A bunch of men in an open field is a ground point target, one tries to put HE in the middle or close to it. Curving trajectories are better at walking in rounds till they land where one wants, due to a smaller change in ground location per change in gun elevation. Are low velocity howitzers or high velocity guns better at short range HE fire against ground points?
All the data we have seen points to low velocity.
Our earlier posts pointed to 810 m/s 88L56 HE and 750 m/s 75L70 HE.
I don't think that you understand this and all the explanations in the world won't help.
We have German ballistic tables, computer analyse's and pretty good logic on our side.
Where is your mathematical analysis? We have the original Diehl articles, you have a web site based on Diehl.
If you carefully read our previous posts on German HE explosive weight you would see that we have the Diehl article and used it, and ten years ago when we read Diehl we were left with an opinion regarding 75L24 HE that recent re-reeading supported.
The points you have brought up proved to be valuable and lead us to some good sites, and we appreciate your assistance. Most questions help open doors, and suggest new research paths.
We cannot, however, continue to correct your misstatements and distortions since we have a booklet on armor penetration to finish. If your make a substantive statement we will respond, and we are going to follow-up on German 75mm HE. Otherwise, we have said all that we are going to in response to your posts and await your analysis of HE trajectories (specifically 88L56 and 75L70 HE vs. 75L24 HE).
You disagree, we made our case, case closed until new evidence is provided.
-
Since tungsten core (HVAP) penetration tests by America (and others) were at a constant close range and varied velocity through powder charge, range effects would not show up during firing tests at simulated range in meters.
U.S. tests for 76 and 90 HVAP generally show same slope effects with changes in velocity, only great variation is 90 HVAP at 55°, which might have been due to other factors (45° and lower angle hits had constant slope modifiers as velocity varied).
Thing about APDS slope effect is that it is alot lower than other tungsten core rounds. But it also would be alot higher when the sabot stuck, which would also destroy accuracy.
So inaccurate APDS also had bad or no penetration. This should be a part of CM, the inconsistency of APDS. As noted before in my posts. Jentz states that APDS "was not particularly accurate".
Irregular APDS is all we ask. Make it miss Panthers and Tiger II's at 200 yards, and bounce off PzKpfw II's when it does land on something. Not all the time, maybe half.
And don't forget the cracked Panther glacis after 17 pounder hits, this can be shown on the little tanks.
And how about Panther armor quality that only penalizes the glacis.
And....................
Good night.
-
Lewis,
My source is Diehl's articles, mistakenly used Dietz.
Diehl's original articles stated that 75L24 used different HE than 75L70 and 75L48. Did that web site you were so kind to note make a mistake copying Diehl's information. Diehl seemed pretty clear in stating that German 75mm HE was not equal in all cases.
When I originally read Diehl's articles and studied them in depth about 10 years ago, it seemed logical that 75L24 HE would have more 60/40 Amadol than Panther 75.
Thank you for the web site address, the penetration data is consistent with our own DeMarre estimates from British test of Panther 75mm and U.S. 75mm.
Now, if you could find a site that discussed the relative ground point target accuracy of low and high velocity HE. Did 88L56 HE, fired at 810 m/s, have as much explosive as 75L24?
We await your response.
-
Lewis,
Posted my source, Dietz' articles from late 60's or early 70's.
Dietz indicated the following:
75L24 HE .853 kg 60/40 Amadol
75L70 HE .654 kg 60/40 Amadol
Based on weight of explosive it would seem that Panther HE is equivalent of Sherman 75mm TNT, but we are not sure that 60/40 Amadol is equal to U.S. TNT.
The basic issue regarding accuracy against ground point targets has still not been successfully disproved.
Basic summary:
Wargames should have two HE accuracies, one against ground point targets and one against vertical targets. And the accuracy against vertical targets would have to include tanks, since HE was fired in attempt to damage running gear.
Low velocity HE is more accurate against a wide range of ground point target types, and low velocity HE usually packs more wallop than higher velocity HE shells. General rule.
-
The search on the salts site is for "penetration". First site that shows up is the one to go to.
-
If you go to
http://www.britwar.co.uk/salts/salt6.htm
do a search, and then open up the first address, there is a massive amount of WW II penetration data.. Close to the bottom is APDS slope multipliers at 30° and 60°, and CM underestimates APDS slope effects by quite a bit.
CM uses about 3 at 60°, the salts site has 3.53 at 60°. Tungsten was very brittle (and very hard, which often is associated with brittle behavior, like glass sheets), and be impacted more by angle than steel.
CM appears to underestimate the resistance of Panther and Tiger II armor, and the need to revise slope figures should be examined.
Tungsten slope effects should be substantially higher than AP or APCBC, as a general rule. However, at T/D=1 and 60°, AP slope effect is 4.00 compared to 3.00 for APCBC and 3.54 for APDS, so the general use has to be used with care. But how many steel AP rounds can penetrate 4 times their diameter without shatter?
We would note that the 60° sloe effect for U.S. HVAP is about 4.3 and much higher than APDS, which might be due to the carrier, nose shape or cap.
-
The beaten zones for HE fire by 75L48 and 88L56 are significantly different at 500m, and a realistic scenario might have both tanks firing HE at a human wave attack on the Ostfront.
Level ground is make-believe, to a degree, but the basic principles hold. Arching fire has less chance of a major undershoot or overshoot for equal dispersion and range estimate, and is more dependable when it comes to corrections or bracketing. We've run computer runs on this, and it looks plausible.
75L24 carried a heavier load of explosive than U.S. 75mm HE fired by Sherman. 1.91# explosive for 75L24 HE, 1.47# for U.S. 75mm HE. 75L24 HE carries about 30% more explosive by weight.
75L24 carried more explosive than 75L70, 0.85 kg vs. 0.65 kg, so lower muzzle velocity 75L24 HE carries 30% more explosive than Panther HE.
A fellow named Dietz ran a series of articles on German ammo, and guess what, 75L48 HE has different amount of explosive compared to 75L70 and 75L24 HE. German 75mm HE did not all carry the same load.
Another case (in a long string) that supports the theory that low velocity is normally associated with more explosive power, and also gives one better accuracy against ground point targets.
75L24 was a superb close support weapon despite a round trajectory. Good combination of HE explosive power and a nice ballistic arch to the flight path.
Grog Data on "Natter GAP"
in Combat Mission Archive #3 (2001)
Posted
Funniest parody I've ever seen!
Now I'am afraid to post anything!