Long 88mm lacking punch?

[Paul Lakowski]

Finally some one is beginnig to see the nature of just who hard the problem is, Thanks Rattus

<BLOCKQUOTE>quote:</font><HR>Originally posted by Rattus:

I understood the US Army usd the "through crack" ballistic limit until the end of WWII and thereafter introduced the "specified damage to thin reference plate..." limit. It did not use the US Navy's ballistic limit of "complete penetration".

<HR></BLOCKQUOTE>

Yes you might be right, but Claus Bonnesen posted a set of 90mm ammo charts , that clearly state 'NAVY criteria' on the top right had corner....so if anything this complicates matters further.I'll have to dig further cause I remember reading that this was changed in 1955.

Can any one tell what criteria Sopwiths formula is based on?

<BLOCKQUOTE>quote:</font><HR>

This means that penetration figures even for US Army equipments tested before/during and after the war are not directly comparable. I assume(!) the British tests used the "complete penetration" limit - their naval testing was obsessed with penetration with shell remaining in a condition fit to burst.

<HR></BLOCKQUOTE>

So that suggests that 80% success like the Russian tests. I remember the Charm 3 round for the Challenger -2 was listed as 700mm @ V50 ballistic limit @ 2km range...I guess they changed some where along the road.

<BLOCKQUOTE>quote:</font><HR>

Unless the Germans also used comparable ballistic limits the German proof figures are not comparable to those conducted by the US and UK. Different German proof test may also have had different ballistic limits. Even if they all used (for example) the "specified damage to thin reference plate..." ballisitc limt, there is enormous scope for difference in the required amount of damage to the reference plate and the distance the reference plate was positioned behind the armour plate.

The fact that target plates have different brinnel hardnesses is another problem (I assume the plates were face hardened). If the plates were not of the same quality (metallurgical flaws, rather more important for face hardened armour than homogenous armour), if the plates were not of constant hardness, to what depth did the hardening extend - how deep was the transitional layer...Again unless these are constant between the different testers the comparisons are very difficult.

Finally, whilst the ogive, hardness and nose height (as Paul noted) are important and will effect penetration of otherwise identical shells, the same is also true of the shape and hardness of the armour piercing cap against face hardened armour. This is complicated by the fact that the shape/hardness of both cap and shell will be more or less optimised (effective)for a particular range of impact angles. A design which works well over (say) 0-30 degrees will not be as effective over 30-60 degrees, so whether you perform the test at 30 degrees or 0 degrees is important. The shape, particularly of the cap, is also important in detemining if the shell richochets or not - especially when considering impacts at higher angles of impact. Simple scaling of results to compensate for differing slopes will not suffice even for the same projectile, let alone ones with different ogive/caps/hardness...

My point is that proof tests such as quoted earlier by different testing bodies are extremely difficult to compare without prodigious ammounts of imformation, probably no longer available.

The values given for the penetration of the 88/71 therfore do not seem to be inconsistent given the variables discussed above (and I did not mention shell quality, barrel wear..).

The Jentz figures do not have to be "wrong" (or anyone else's), they may accurately represent a particular behaviour under what are unique circumstances (that series of tests).

This might mean that CM is lousy at modelling that situation but great for the other 95% of the time.

Since the aliies do not seem to have produced a gun/shell with sufficiently similar shape/hardness/calibre/velocity to that of the 88/L71 at the same velocity an easy test comparison is impossible.

Michael<HR></BLOCKQUOTE>

I couldn't have reported it better

I would only add that Jentz touches on German test methods, and the implication [ that I read] is that they take a average of a number of shots to determine a value , which sounds exactly like the methods reported in the Impact Engineering Journals. In the journals a simple test involves 3-6 shots with the data point being the average, but I understand this small number is only possible with aid of computer sims. If you read the material on 's curve' distributions I mentioned before they use some thing like 70-150 test shots all on the same target obliquity and range etc.

[Paul Lakowski]

This is from Karl Brandel.

"you find the test of the KWK43 against the Tiger II frontal turret armour which it perforated completely (185mm). It exited

the tank through the rear turret armour (80mm IIRC = > 265mm at nearly the vertical) (8^)."

Now this could be within 20% of 230mm vertical penetration value @ 100m but how would you stretch this to 170mm?

[PzKpfw 1]

1. Do agree that several different, and independently credible, sources have produced different results for the same weapon?

Yes; but since BTS doesnt use these sources or even LF test data as stated by Charles & the original argument compared Jentz vs Jentz data how does this question concern the original claim?.

3. Do you agree that it is inherently flawed to pick one set of the credible numbers over another set without any other reason than

blind faith that the one you are picking is correct?

The original claim was that Jentz's numbers were flawed, no mention of any other source was made. As Jentz's data is from German wartime Wa Pruf, Waffamt reports you are questioning it, Steve not us; their is no "Blind Faith" agrument you can't have

one as your replys qualify for it as well.

You have provided no Formula here as proof of your original claim that the 8.8cm KwK.43 ammunition tests are flawed. You have cited the British 1950 report as absolute proof yet no page number has been given or the time taken to type the formula from it that tells us the ammo tests are flawed. etc.

4. Do you agree that our physics model is only in dispute in relation to the 88L/71 data that you support. Not to any other data from any other weapon from any other nation?

No because I havent gone thru and matched all CM weapons to actual test results, do you realy want us to start digging into this? as it may open a whole new can of worms, while we haven't even proved or disproved the 8.8cm ammunition test results yet.

7. Do you agree with the scientific approach that when you have differing data, from credible sources, that you must look to another scientific (or primary source) to explain which of the conflicting data sets is correct?

No each country used diferent test methods. Wa Pruf & Waffamt documents are Primary source material and they have been ruled invalid here because the results disagree with your formulas results, in essence this rules that all primary sources are invalid except the ones you deem are correct, you can't have it both ways.

8. Do you think it is more probably that there is one set of questionable data for the 88L/71 or that all the other test results,

for all weapons from all countries, is in error?

No again each country had its own criteria for testing with diferent processes and results useing the same guns and ammunition as I pointed out.

9. If our equations are outdated and inaccurate, can you please explain how it is that our results match those of test data from three different nations for dozens of guns? Put another way, how can a flawed set of equations come up with the correct results and still be flawed?

This assumes you accept LF test data as accurate which you have stated you dont accept or even use LF data in CM, so how can you use it here to substantiate your claim that the 8.8cm Kw.K 43 LF tests are flawed as well as ignoring every country used diferent standards.

10. Which is more credible; blind faith that can not account for differing data or mathematical results, or a reasoned scientific approach that can account for everything using primary materials AND mathematical computations?

Neither they both have to be used together to draw an conclusion, with a suitable margin for error factored into the equasion.

Now I didn't want to comment on this again till I got the page numbers etc but as I'm lumped in with the much maligned group......

Regards, John Waters

------------------

People who can smile when things go wrong

have found someone else to blame.

[Juardis]

<BLOCKQUOTE>quote:</font><HR>Originally posted by PzKpfw 1:

8. Do you think it is more probably that there is one set of questionable data for the 88L/71 or that all the other test results,

for all weapons from all countries, is in error?

No again each country had its own criteria for testing with diferent processes and results useing the same guns and ammunition as I pointed out.

<HR></BLOCKQUOTE>

That's why I said in an earlier post to this thread that ideally, you'd want all the data from a single source. However, you guys have seemingly given a plausible explanation for why the 88L71 penetration data is greater than other data. If true (that there is a physical reason the test data is an outlier), then this suggests the equation is good for everything BUT the 88L71. Even so, and I think this has been mentioned already, it doesn't mean diddly in CM1. Depending on the ranges in CM2 though, it could mean diddly . I love this thread.

What I'd like to know though is does the Covington and Aberdeen data show a similar "bump" in the curve? (Remember, ideally you want to use ALL the data from ONE institution, not all data lumped together).

------------------

Jeff Abbott

[:USERNAME:]

I again throw the variable into the mix of differing spin of the shell. From an engineering standpoint it could be argued that it would resist a change in direction or a sloped armor "fighter". Rotation energy and translational enegies both add to a shells total kinetic energy. A spinning object does not apreciate changes of direction but my feeling is that velocity over rules anywaay.

Lewis

[Juardis]

<BLOCKQUOTE>quote:</font><HR>Originally posted by :USERNAME::

I again throw the variable into the mix of differing spin of the shell. Lewis<HR></BLOCKQUOTE>

What do you mean Lewis? There are only 2 directions a shell can spin, clockwise or counter-clockwise. I see no reason why one would differ from the other. Is that what you mean?

[Paul Lakowski]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Juardis:

That's why I said in an earlier post to this thread that ideally, you'd want all the data from a single source. However, you guys have seemingly given a plausible explanation for why the 88L71 penetration data is greater than other data. If true (that there is a physical reason the test data is an outlier), then this suggests the equation is good for everything BUT the 88L71. Even so, and I think this has been mentioned already, it doesn't mean diddly in CM1. Depending on the ranges in CM2 though, it could mean diddly . I love this thread.

What I'd like to know though is does the Covington and Aberdeen data show a similar "bump" in the curve? (Remember, ideally you want to use ALL the data from ONE institution, not all data lumped together).

<HR></BLOCKQUOTE>

Jeff in theory if you know the testing criteria you can 'normalise' all the data from different sources ....the engineers do it all the time.

To that end, here's some data on projectile vs common targets of varing hardness at increasing velocity.

The results are all referenced to RHA being a value of 1.0 and are from the "Journal of Materials Processing Technology"- Vol96 , pp 81-91.

<PRE>

Steel 400m/s 800m/s 1200m/s 1600m/s

[110 BHN] 0.5 0.67 0.77 0.8

[280 BHN] 1.0 1.0 1.0 1.0

[ 430BHN] 1.8 1.57 1.38 1.25

</PRE>

This suggest the change in BHN at each striking velocity should be [ over 110-430 BHN ].

<PRE>

320/130 = ~4 % every 10 BHN change @ 400 m/s [1320 ft/s].

320/90 =~3% every 10 BHN change @ 800 m/s [2640 ft/s].

320/61 = ~2% every 10 BHN change @ 1200 m/s [3960 ft/s].

320/45 = ~1% every 7 BHN change @ 1600m/s [5280 ft/s].

[This message has been edited by Paul Lakowski (edited 08-25-2000).]

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Juardis:

What do you mean Lewis? There are only 2 directions a shell can spin, clockwise or counter-clockwise. I see no reason why one would differ from the other. Is that what you mean?

<HR></BLOCKQUOTE>

No.

Its like a gyroscope. It dont like you changing its direction of axis. Maybe someone else can explain it simpler?

Lewis

[Ben Galanti]

PzKpfw 1 said:

<BLOCKQUOTE>quote:</font><HR>This assumes you accept LF test data as accurate which you have stated you dont accept or even use LF data in CM, so how can you use it here to substantiate your claim that the 8.8cm Kw.K 43 LF tests are flawed as well as ignoring every country used diferent standards.<HR></BLOCKQUOTE>

John, I don't quite follow the logic here. In CM, everytime a shell is fired, the game cranks through the Ordance Board equation, that's why the data isn't just plugged in. Using the equation instead of test values allows you to figure out penetration at 42 degrees at 271 m, instead of the small number of values given for the test. So, the game basically HAS to use an equation. The values shown in the info screen are the results of the program, not the data that BTS entered. I don't believe that they can jsut jump in and plug in values as they see fit.

BTS never said that they "don't accept" LF data. In fact, the way the validated the use of the equation is checking it against life fire data. They never said that LF data is bad, but only that it seems odd that this equation matches up to pretty much all the other LF data other than the 88L71. Now, this could be becuase either the equation is flawed or the test was flawed. BTS believes that the test was somehow flawed (not out of the question, maybe the armor plate was bad, maybe they measured wrong, who knows..). They believe this becuase the equations seems to work for other guns. You believe that the equation is flawed (also not out of the question, maybe there is something about the 88L71 which is not accounted for in the equation, the ogive shape, it's velocity, or something else...).

Now there are only a couple of ways to prove this point. To prove that the LF data is good (or bad), the tests would have to be redone, which is impossible. To prove that the equation is good (or bad), it's results need to be compared to a multitude of LF data. So the best way to show the equation is flawed is to look at the other guns in the game and compare them to the results given by the equation. I suspect that the ordance board report also defines what it considers a penetration, so you would have to take that into account when comparing it to test data. If you then saw that the equation results didn't match up with the test results, you could state pretty confidently that the equation was flawed (and would have a pretty nice paper to publish to boot )

Now, if it can be shown that this equation is flawed, I'm sure BTS would be interested in that...

Ben

[Andrew Jaremkow]

THE FORMULA

Since the users of the formula have so far declined to either post it, or give reference to where in the Ordnance Board report the equation is, I thought I'd take a stab at identifying it. That way we can all apply the appropriate data and draw conclusions, rather than simply taking the blanket assurance being offered to us.

As far as I can tell the equation being discussed is the National Physical Laboratory Formula for Normal Attack, described in Chapter 2, Section 4 of the report. It comes in the form (here modified for angled impact):

(Wv^2)/d^3 = {[43.4*B^0.5*(t/d)*sec 3/2 theta]+747-[54000/Bo-B]-[182theta/(65-theta)]}^2

where:

W = shell weight

v = shell velocity

d = shell diameter

t = plate thickness

theta = angle of impact

B = plate hardness (Brinnell)

Bo = limiting hardness

The limiting hardness can be derived with reference to the standard 2 pdr shot used to derive the equation, using the following formula.

Bo = 500 - 160 log(d/d2)

where d2 = 1.565 inches, the diameter of 2 pdr shot.

The model is considered to apply for A.P. shot up to 6 inches being fired against homogenous armour in the 200 to 400 Brinell range, at angles up to 45 degrees.

The model was first developed from 1942 firing trials of 2 pdr shot (1.565" dia), and later expanded with 1943 and 1944 testing of three subscale AP rounds of the 2 pdr shape (0.990", 0.540", and 0.296" dia). Shots were conducted against 3% Cr.Mo. steel plates up to 2 diameters thick, and ranging from Brinell 250 to 450. Later on, in work that continued into 1947, trials were conducted with 6 pdr, 17 pdr, and 3.7" shot, and these confirmed that the model was generally accurate for AP shot. The formula's accuracy was found to be better than 2% velocity (roughly 21 f/s), so long as the baseline 3% Cr.Mo. steel was being used, but when other types of steel were used as a target the formula's accuracy dropped, and deviations of as much as 150 f/s were noted.

The model has several limitations. It can only compensate for mass, diameter, and velocity of the projectile, and hardness of the target plate. It cannot distinguish between rounds with different nose shapes, different hardnesses, and different materials, nor does it predict the angle-dependant performance of features such as armour piercing caps. It does not predict the performance of face hardened armour. Its correction for angled armour is a fairly clumsy fit (sec 3/2 theta) when you compare it to charts of penetration vs. angle, with their complex curves.

If this is the wrong equation, I apologize, but I suspect it's the one. The only other options are modified DeMarre formulae, which seem even less likely to provide good results across the board.

Limiting Velocity

The report has the following to say about definitions of penetration:

"The term "perforation" cn be defined in many ways, according to the stage at which defeat of the plate is considered to have occurred. Thus the "ballistic limit" of a plate is that velocity above which a given shot will produce a cracked bulge, and below which it will produce and uncracked bulge. The "critical velocity" used in this chapter, however, is that corresponding to exact perforation with no residual velocity after the shot has perforated the plate, i.e., the minimum velocity at which the shot passes clean through the plate." (Emphasis mine)

88L71 vs 88 L56

I'm not an expert on WWII shells (I usually concentrate on modern ammunition), so, like some others here, I was wondering if someone could post details of the size, shape, composition, hardness, etc. of the shells for the L71 and the L56. Are they identical shells, or was there a significant difference between them? If the shells were identical we should be able to plot a penetration vs. velocity curve (not range) for both guns, AND THEY SHOULD MEET AND OVERLAP. If the curves do not overlap, then there are obviously discrepancies between the two sets of data. Of course, if the shells are of different designs we cannot do this, since each shell will behave differently at the same speed.

Does anyone here have the data to check this?

[This message has been edited by Andrew Jaremkow (edited 08-26-2000).]

[PzKpfw 1]

Hi Ben great post & think its time for me to clarify my position in this whole circus as I think its been lost in the ensuing flood of posts.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Ben Galanti:

John, I don't quite follow the logic here. In CM, everytime a shell is fired, the game cranks through the Ordance Board equation, that's why the data isn't just plugged in. Using the equation instead of test values allows you to figure out penetration at 42 degrees at 271 m, instead of the small number of values given for the test. So, the game basically HAS to use an equation. The values shown in the info screen are the results of the program, not the data that BTS entered. I don't believe that they can jsut jump in and plug in values as they see fit.

<HR></BLOCKQUOTE>

Ben I understand that I wouldn't ask them to. my point in this has not been to say Charles & Steves data is bad.

I questioned Charles statement that the German live fire tests concerning the KwK.43 ammunition was bad & I think thats been forgotten or lost here.

I was not challengeing CM's formulas but, a statement concerning the test results.

Charles statement concerning the test data intrigued me as the numbers have been accepted for years in the wargameing community & books to learn if he was correct & if he was; to add it to my knowledge as I added his 12.8cm L/55 pen data to my records.

As anyone who since disagreed with Charles original post; was told provide proof his conclusion was wrong, I asked the same of him.

This request did not concern or imply CM formula was flawed. My request was that if the actual KwK.43 live fire tests were wrong please provide me with how you reached that conclusion Ie, formula documentation.

To date all I have is Charles statements concerning why the data is wrong, because of propriatary constraints BTS can not provide me with the data I seek, and tell me they have already provided sound scientific evidence to prove their claim.

Now I ask anyone go back and read what charles originaly posted. Ben, read every post from Charles & Steve. If I'm missing the post that provided the above said evidence; that the original Wa Pruf tests were wrong Please point out what I have missed & Ill read it apologise for wasteing bandwidth & shut up .

The focus do far has been on stateing CM's formula integrerty; This doesnt concern me, all I'm concerned about is learning if the the KwK 43 ammunition tests were actualy flawed.

To this end I have asked for the page numbers etc in the 1950 Report that provide the data on the flawed K.wK.43 tests.

<BLOCKQUOTE>quote:</font><HR>

They never said that LF data is bad, but only that it seems odd that this equation matches up to pretty much all the other LF data other than the 88L71.

<HR></BLOCKQUOTE>

Your correct Ben I read that wrong and took a literal from reading the below:

<BLOCKQUOTE>quote:</font><HR> We don't, because CM - I will say this YET AGAIN because some people aren't listening! - DOES NOT USE TABLE-BASED PENETRATION DATA! <HR></BLOCKQUOTE>

For that I apologise. But I'm also concered Ben, that test numbers from Aberdeen etc are being used when they fit the formula to prove Charles claim was correct.

That was my main complaint how can you tell me that I cant trust Jentz's (Wa Pruf) 8.8cm data; but I can trust Jent'z L/48 & L/70 data. Or that since Aberdeens data matches the formula the German wartime test data for the 8.8cm is irrefutably incorrect Does anyone see my point? I'm confused why contrary results are dismissed so readily yet other results from the same source used.

<BLOCKQUOTE>quote:</font><HR>

Now, this could be becuase either the equation is flawed or the test was flawed. BTS believes that the test was somehow flawed (not out of the question, maybe the armor plate was bad, maybe they measured wrong, who knows..). They believe this becuase the equations seems to work for other guns. You believe that the equation is flawed (also not out of the question, maybe there is something about the 88L71 which is not accounted for in the equation, the ogive shape, it's velocity, or something else...).

<HR></BLOCKQUOTE>

I agree again I'm not disputing their formula I'm asking for proof; hard readable proof that the test data was fudged, we all know how meticulous German record keeping was especialy at their test facilities.

Again I want to reinterate this clearly; my interest in this discussion is simply to find out if the original WW2 Wa Pruf K.wK.43 8.8cm penetration tests are flawed pursuant to Charles original post..... Thats it folks, no agenda, no conspiracy, nada, nianti .

<BLOCKQUOTE>quote:</font><HR>

Now there are only a couple of ways to prove this point. To prove that the LF data is good (or bad), the tests would have to be redone, which is impossible.<HR></BLOCKQUOTE>

And thats all I'm concerned with Ben, Charles original statement was that they were wrong, I merely want the data that proves this, and hopefuly the requested page numbers will do it.

I hope this has explained my position on this debate clearly.

Regards, John Waters

-----------

"Go for the eyes Boo, go for the eyes!!".

[This message has been edited by PzKpfw 1 (edited 08-26-2000).]

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Andrew Jaremkow:

THE FORMULA

Hi Andrew good to see you. Thanks for takeing the time to come & thank you for the data this gives something to go on & may help me understand better.

Anyone got a copy of DA TM 9-1985-3/DAF TO 39B-1A-10 "GERMAN EXPLOSIVE ORDNANCE (PROJECTILES AND PROJECTILE FUZES)" lying around? that would probably provide the length, weight etc.

The model has several limitations. It can only compensate for mass, diameter, and velocity of the projectile, and hardness of the target plate. It cannot distinguish between rounds with different nose shapes,

different hardnesses, and different materials, nor does it predict the angle-dependant performance of features such as armour piercing caps.It does not predict the performance of face hardened armour. Its

correction for angled armour is a fairly clumsy fit (sec 3/2 theta) when you compare it to charts of penetration vs. angle, with their complex curves.

<HR></BLOCKQUOTE>

Thata a very, interesting read Andrew am I wrong in assuming that German FH test plate would provide diferent results that the report could not emulate?.

It also brings up Robert's telling us that the reports angle/slope equasions were incorrect and you had to use another way to establish them.

And how does this affect German test data results vs the limitations of the formula?. Could the 8.8cm Kw.K. 43 Ammunition have reache its spec ified penetration values as repoted by Wa Pruf is my main question.

Regards, John Waters

------------------

People who can smile when things go wrong

have found someone else to blame.

[This message has been edited by PzKpfw 1 (edited 08-26-2000).]

[Paul Lakowski]

Sure is good to see Andrew .

Looking at the primitive photos and diagrams of the 88mm rounds I get.[Jentz 'Germanys Tiger tanks'].The 88 Pzgr 39/KwK 36 [Tiger 1] has what appears to be 396mm long ogive 4.5:1 L/d projectile with a 0.25-0.26 tip to body diameter or about 4:1.

Looking at other German warheads this is similar to the all the German 75mm Pzgr

rounds.For the 88 pzgr 39/KwK 43 [Tiger 2 ]I get 0.19-0.21 or about 5:1 tip to body radius.

Rereading Brooks work and examining the accompaigning pics its evident that at the transition velocity where the penetration curve 'rebounds' seems to conform with the projectile penetrating in a 'Yawed' fashtion.

Looking at the Int.J.Impact Engng Vol-23 pp 723 -734. Piekutowski et al. They seem to be showing the same event with ogive Steel 10:1 rods impacting aluminum targets. This is ridgid penetrator vs ductile target models.

In addition in both Brooks and Piekutowskis work ,the penetrator with the harder metal delayed the onset of this transition velocity and achieved higher penetration overall and a sharper penetration - velocity curve. So even a small change in the ballistic cap of the 88L71 combined with higher velocity could have resulted in a much higher penetration, compared to 88L36 round.

What I suspect is going on is that the exact deformation of the ogive is creating an imbalance in the penetration leading to this 'Yawed' type penetration.

In all cases [ so far checked]with flat tip rods or ogive penetrators with completly deformable tips , there is no noticable transition zone.

[cbo]

First of all, I am not math nut and I do not (currently) play CM but the discussion about the 8,8cm KwK/PaK 43 penetration being either "doctored", obtained under circumstances different from other German data etc. is interesting.

I do have a couple of questions I hope someone can answer.

1: Are there any WWII-era test data that backs up the results of the CM formula for the 8,8cm KwK 43?

2: If so, are there similar results obtained under the same circumstances for the 7,5cm PaK/KwK 40 and KwK 42 and do these correspond with the results of the game formula for these guns?

3: What are the CM penetration data for the 8,8cm KwK 43 L/71 at an angle of 0 degrees at 100m, 500m, 1000m, 1500m and 2000m?

I went over whatever data I had for the KwK 43, most of it originating in WWII primary sources. While most of it appears very similar, there are some destinct differences in the penetration curves that the numbers produce, which seems to indicate that some of it is not actual firing data, but rather calculated data using some form of simplified formula (compared to both the CM formula and what others have posted).

Claus B

[PzKpfw 1]

Wow Claus, good to see you. .

<BLOCKQUOTE>quote:</font><HR>Originally posted by cbo:

I do have a couple of questions I hope someone can answer.

1: Are there any WWII-era test data that backs up the results of the CM formula for the 8,8cm KwK 43?

<HR></BLOCKQUOTE>

IIRC Aberdeen data does.

<BLOCKQUOTE>quote:</font><HR>

2: If so, are there similar results obtained under the same circumstances for the 7,5cm PaK/KwK 40 and KwK 42 and do these correspond with the results of the game formula for these guns?

<HR></BLOCKQUOTE>

Dunno IIRC Charles used Jentz data in his original post for the L/48, L/70 & L/71 comparison and the L/48 & L/70 matched CM data.

<BLOCKQUOTE>quote:</font><HR>

3: What are the CM penetration data for the 8,8cm KwK 43 L/71 at an angle of 0 degrees at 100m, 500m, 1000m, 1500m and 2000m?

<HR></BLOCKQUOTE>

8.8cm KwK.43 CM penetration data @ 0^

100ms - 220mm

500ms - 205mm

1000ms - 188mm

2000ms - 157mm

Their is no 1500ms range listed in CM Claus.

<BLOCKQUOTE>quote:</font><HR>

I went over whatever data I had for the KwK 43, most of it originating in WWII primary sources. While most of it appears very similar, there are some destinct differences in the penetration curves that the numbers produce, which seems to indicate that some of it is not actual firing data, but rather calculated data using some form of simplified formula (compared to both the CM formula and what others have posted).

<HR></BLOCKQUOTE>

Interesting Claus is it similar to the L/70 curve I saw a comment that the L/70 curve didn't match up either.

Regards, John Waters

------------------

People who can smile when things go wrong

have found someone else to blame.

[cbo]

<BLOCKQUOTE>quote:</font><HR>Originally posted by PzKpfw 1:

Wow Claus, good to see you. . <HR></BLOCKQUOTE>

You too John

You mentioned that "Aberdeen data" backed the CM results. What exactly is "Aberdeen data"? Is it posted somewhere in this thread? I have some of Roberts data from a US Army February 1945 report, but this does not support the CM figures.

Thanks for the CM 0deg figures, I'll go type them in and see what happens...

Claus B

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by cbo:

You too John

You mentioned that "Aberdeen data" backed the CM results. What exactly is "Aberdeen data"? Is it posted somewhere in this thread? I have some of Roberts data from a US Army February 1945 report, but this does not support the CM figures.

Thanks for the CM 0deg figures, I'll go type them in and see what happens...

Claus B

<HR></BLOCKQUOTE>

Yes its been a long time .

The Aberdeen data wasn't presented as table range/penetraton only the below statement from BTS:

<BLOCKQUOTE>quote:</font><HR>

However, one set of data from Aberdeen supports our numbers, derrived from the same equations that came up with all the other correct numbers.

<HR></BLOCKQUOTE>

What did the Febuary 45 US Army tests report that Robert gave you Claus?.

Regards, John Waters

---------

"Go for the eyes Boo, go for the eyes!!".

[This message has been edited by PzKpfw 1 (edited 08-26-2000).]

[Ben Galanti]

John,

Thanks for your post. That does clear things up for me. I think people are arguing two different things in this thread, and that's why it's broken down. I thought all along it was a question to whether CM models the 88L71 correctly...

Claus, there's a post from 'Desert Fox' on page 2 of this thread, which lays outand compares a variety of 88L71 data.

[cbo]

<BLOCKQUOTE>quote:</font><HR>Originally posted by PzKpfw 1:

What did the Febuary 45 US Army tests report that Robert gave you Claus?.<HR></BLOCKQUOTE>

It is a long list of German pen data in inches, ranges in yards at 0deg and 30deg. The data is fragmentary, but for the 8,8cm KwK 43 the numbers available corresponds with the German data.

It would be interesting if the CM people would post the 8,8cm KwK 43 APG test firing data that backs up their figures.

OK, as I said before, I am not a math nut, half of what Paul and Andrew writes are miles above my head - I get the principle but rarely the technicalities. So bare with me if this is somewhat simplistic.

First I tried to find out whether the 8,8cm data I have are test data or calculated data.

It appears that WWII calculated data, at least the German variant, does not take T/D into account when calculating 30deg figures from 0deg figures. The ratio between the 0deg values and the 30deg values remain constant regardless of penetration.

In the case of some German calculations of the Soviet 85mm gun, the ratio was 1.22-1.23. Looking at testdata for the US 76mm gun, the ratio goes from 1.32 to 1.17, for the 90mm from 1.27 to 1.20 and so forth. Here came the first surprise. Data found in Hogg and Senger und Etterlin forthe 8,8cm KwK 43 showed a constant ratio of 1.14 between the 0deg and the 30deg values while those from Spielberger (see below) varied from 1.08 to 1.14. I would suggest that this means that the 30deg data found in Hogg and Senger und Etterlin are calculated data, not real test firing data.

Jentz only posts his 30deg figures, at least I've never seen the corresponding 0deg figures. However, in his book on the Panther, Spielberger shows both 0deg and 90deg figures for the Jagdpanthers 8,8cm PaK 43 gun, the original source being "Kraftfahrwesen e.V, Fachauschuss Wehrtechnik, Oberst a.D Theodor Icken". Icken was with WaPrüf 6. Spielbergers and Jentz 30deg figures vary only with a few mm and both apparently comes from WaPrüf, so I assume they are likely to come from the same source.

Here comes the funny part:

Spielbergers figures for 0deg are:

100 - 220

500 - 205

1000 - 186

1500 - 170

2000 - 154

CMs figures for 0deg are:

100 - 220

500 - 205

1000 - 188

1500 - N/A

2000 - 157

So the German wartime data for penetration at 0deg is not in conflict with CMs data. It is in the calculation of the slope effect at 30deg that things go wrong.

Spielbergers figures for 30deg are:

100 - 203

500 - 182

1000 - 167

1500 - 150

2000 - 135

CMs figures for 30deg are:

100 - 177

500 - 165

1000 - 151

1500 - N/A

2000 - 121

The relationship between Spielbergers 0deg and 30 deg figures range from 1.08 to 1.14 while CMs range from 1.24 to 1.30. Looking at the 76mm, 90mm and 17pdr they all have a ratio between 0deg and 30deg around 1.20 to 1.30 while the 8,8cm KwK 43 is down at 1.08 to 1.14 and thus appears to be less effected by slope.

Why?

Claus B

[Kurtz]

When reading the formula (it almost made my head hurt!!!) posted by Andrew Jaremkow I noticed that the rotation of the projectile isn´t included in it.

I came to think about this after reading Lewis' post about rotationally stabilized projs being more stable and therefore able to penetrate more. (This was how I undestodd his post) It was my understanding that a rotating proj would have a tendency to change direction on its way through the armour, if it didn´t hit at a right angle, the proj would strive to move perpendicular to the armor plate.

This leads to two questions, admittedly not directly connected to the 88/L71, which I hope someone can answer:

1. Will this curved movement increase penetration due to the fact that the proj will exit the armour as fast as possible or is penetration lower due to energy losses (energy conversions, I know) when the proj does not move in a straight path?

2. Is this tendency dependent on how fast the proj rotate?

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Ben Galanti:

John,

Thanks for your post. That does clear things up for me. I think people are arguing two different things in this thread, and that's why it's broken down. I thought all along it was a question to whether CM models the 88L71 correctly...

<HR></BLOCKQUOTE>

No thank you Ben for takeing the time to read my posts and see my intent.

Exactly Ben, and thats why I disagree with my being generaly lumped into some conspiracy group theory thats, 'dodgeing questions' etc. As I never intentionaly questioned the CM 8.8cm KwK.43 formula pentration data.

Regards, John Waters

---------

"Make way evil, I'm armed to the teeth and packing a hamster!"

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by cbo:

I would suggest that this means that the 30deg data found in Hogg and Senger und Etterlin are calculated data, not real test firing data.

<HR></BLOCKQUOTE>

It would appear so Claus.

<BLOCKQUOTE>quote:</font><HR>

Jentz only posts his 30deg figures, at least I've never seen the corresponding 0deg figures. However, in his book on the Panther, Spielberger shows both 0deg and 90deg figures for the Jagdpanthers 8,8cm PaK 43 gun, the original source being "Kraftfahrwesen e.V, Fachauschuss Wehrtechnik, Oberst a.D Theodor Icken". Icken was with WaPrüf 6. Spielbergers and Jentz 30deg figures vary only with a few mm and both apparently comes from WaPrüf, so I assume they are likely to come from the same source.

Here comes the funny part:

Spielbergers figures for 0deg are:

100 - 220

500 - 205

1000 - 186

1500 - 170

2000 - 154

CMs figures for 0deg are:

100 - 220

500 - 205

1000 - 188

1500 - N/A

2000 - 157

<HR></BLOCKQUOTE>

Thats great Claus I'm sure Charles & Steve will be happy.

<BLOCKQUOTE>quote:</font><HR>

So the German wartime data for penetration at 0deg is not in conflict with CMs data. It is in the calculation of the slope effect at 30deg that things go wrong.

Spielbergers figures for 30deg are:

100 - 203

500 - 182

1000 - 167

1500 - 150

2000 - 135

CMs figures for 30deg are:

100 - 177

500 - 165

1000 - 151

1500 - N/A

2000 - 121

The relationship between Spielbergers 0deg and 30 deg figures range from 1.08 to 1.14 while CMs range from 1.24 to 1.30. Looking at the 76mm, 90mm and 17pdr they all have a ratio between 0deg and 30deg around 1.20 to 1.30 while the 8,8cm KwK 43 is down at 1.08 to 1.14 and thus appears to be less effected by slope.

Why?

Claus B<HR></BLOCKQUOTE>

AWSOME Claus, thank you, this does help

As 'Jentz 30^ data for Pzgr.39/43 APCBC

is :

100mm - 202mm

500ms - 185mm

1000ms - 165mm

2000ms - 132mm

Look how close Spielburgers & Jentz's data is. It still raises a question of why theirs a diference off the same data but its a start. Your post helps explain alot when combined with Andrews post.

Now can I have your opinion concerning the validity of the Wa Pruf Live fire tests of 8.8cm KwK.43 ammunition performance as used by Jentz etc, for 30^.

Regards, John Waters

----------

"It's not everyone telling me it can't be done that bothers me. It's them interrupting me while I'm doing it!"

[Paul Lakowski]

Yes its good to see Andrew and Claus . John theres no conspirecy only discussion.What I object to is 'selective use of data' from various sources and dismissing the rest as false or faked, from source that most of us respect.

If CM data from Sopwiths formula is the same as the data Claus reports for normal impact this suggest there using the same penetration criteria which looks alot like the 50% ballistic limit value.

It seems the problem here is the angle , this is exactly what Robert warned me about. In the Ordnance board report they suggest the only way to do a real estimate is on a shot by shot basis, so that part of their approach is sound.The problem here ofcource is that normal impact is rare and angled [ or compounded angled] hits are the norm.

Karl reports the 88 Vs Tiger -II test was at 400m range and examination of the impact shows the front hit about 4 projectile diameters from the gun embrassure which should reduce the front plate armor efficiency to 0.75.The plate hardness is 220 front and 290 BHN rear plate [from Claus website].Going on the previous data on hardness, thats ~2% loss per 10 BHN @ 1000m /s range or 11% loss [275 BHN=> 220BHN] on the front plate leading to 19cm [LOS]x 0.75 x 0.89 = ~12-13cm

The rear plate is 8cm @ 20° [x1.2] or ~9-10cm rear plate.Thats 21-23cm total penetration to say nothing of the fact that the penetration of multiple plates has been shown to reduce total penetration by about 10% @ 800-1000m/s if the gap is 20 times the projectile diameter at normal impact angle.As I see it the gap between front and rear plate is around 35 times the 88 diameter.Thus the penetration needed to achieve this event is on the order of 22cm x 1.1 or ~23-25cm .

Now if we look Claus’s data @ 500m 0° both figures are 205mm average penetration or ~

209mm @ 0° @ 400m range . 2/3 of hits should then result in ± 8% ballistic limit range. This~ 70m/s difference is like a 500m range change, which on the 88L71 is about 20mm difference or 189-239mm .

In 80-90 % cases the value is ± 100m/s change in the ballistic limit , thats ± 900m range or 37mm penetration =172-246mm.range . The extreme 10 % of cases should result of ± 200m/s , which is the same as a <1500m range change or 54mm penetration = 263-155mm range.

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Paul Lakowski:

Yes its good to see Andrew and Claus . John theres no conspirecy only discussion.What I object to is 'selective use of data' from various sources and dismissing the rest as false or faked, from source that most of us respect.

It seems the problem here is the angle , this is exactly what Robert warned me about. In the Ordnance board report they suggest the only way to do a real estimate is on a shot by shot basis, so that part of their approach is sound.The problem here ofcource is that normal impact is rare and angled [ or compounded angled] hits are the norm.

<HR></BLOCKQUOTE>

Nderstood Paul. So this goes back to Robert saying that you had to use another method to obtain the angle/slope data then the formula in the British report?.

Now as the 8.8cm data is the prime arera of contention & despite my not careing about CMs data I did compare the 90mm M304 APCR-T performance at 30^ & 17Pdr APDS to CMs values for this gun as it has been stated that CMs formula consistantly matches the 3000fps & over projectiles source data:

90mm M304 APCR-T @ 30^ Source: Hunnicutt's Sherman.

500yrds 221mm

1000yrds 199mm

90mm M304 APCR-T @ 30^ Source: CM Data

500ms - 231mm

1000ms - 220mm

17Pdr APDS @ 30^ Source: Hunnicutt's Sherman.

500yrds - 208mm

1000yrds 192mm

17Pdr APDS @ 30^ Source: CM Data

500ms - 190mm

1000ms - 190mm

Now this is not saying CMs performance is wrong etc, I'm merely compareing my source for the M304 APCR-T & 17Pdr APDS curve reflected in CM compared to Hunnicutt's data, which is lower then CMs M304 performance, while Hunnicut's data is higher for the 17Pdr APDS.

Regards, John Waters

------------------

People who can smile when things go wrong

have found someone else to blame.

[This message has been edited by PzKpfw 1 (edited 08-26-2000).]

[cbo]

<BLOCKQUOTE>quote:</font><HR>Originally posted by PzKpfw 1:

Now can I have your opinion concerning the validity of the Wa Pruf Live fire tests of 8.8cm KwK.43 ammunition performance as used by Jentz etc, for 30^.<HR></BLOCKQUOTE>

Frankly, I haven't got a clue.

The fact is that no matter how you look at the numbers, the 8,8cm 0deg/30deg values are different from just about anything else. But they do not look like calculated data, the ratio goes up and down like other rounds do:

100 1,08

500 1,13

1000 1,11

1500 1,13

2000 1,14

Spielberger has a table on p. 253 in his Panther book showing penetration curves for the 7,5cm KwK 42 and the 8,8cm KwK 43. The odd thing is that while the curves for the 7,5cm shows both Panzersprenggranate and Panzergranate mit Stahlkern at both 90deg (0deg) and 60deg (30deg), there are only two curves for the 8,8cm: Panzersprengranate and Panzergranate mit Stahlkern at 90deg (0deg). If this table is a truthfull reproduction of the original source for the 8,8cm KwK 43 WaPrüf data, then it does not include 60deg data.

It is difficult to form an opinion about, without having acces to the original data.

What also puzzles me is that while calculated 30deg data for the 7,62cm PaK36r and the Soviet 85mm both uses the 1.23 30deg slope modifier that is straight out of the standard "Neigungswinkeltafel" found on my homepage, the 1.14 value seems odd. I recall Robert referring to the Germans using different tables for different velocities, so I wonder if the 1.14 value used in the calculated 8,8cm PaK 43 30deg data is the 30deg slope modifier found in another table, perhaps the one for 1000 m/s and beyond?

Claus B