Long 88mm lacking punch?

[The DesertFox]

<BLOCKQUOTE>quote:</font><HR>At this point I need more time to study the results, but several things are clear....the shape and hardness of the ogive has a direct baring on penetration perfromance more so than velocity. The narrower and harder the tip the longer the delay in the onset of the 'transitional velocity'. It seems the this is the division between 'modern erosion' type penetration and 'normal' penetration.

I can post Jpegs to that site so I'll focuse on working some thing out there<HR></BLOCKQUOTE>

Yes Paul,

I talked with Claus Bonnesen about the issue. I´d be interested to see them.

Helge

[Lee]

Ah, but I never said that the formula should be taken over test facts.

The whole point here is that the test results themselves have been

questioned as to whether they are indeed "facts" as can be applied

to every day use of the 88 under combat conditions (were the

testers using unusually perfect AP projectiles that guys in the

field wouldn't normally have, were the testers exaggerating?).

If everyone agreed that the tests were showing true results for

the 88 under typical conditions, then there would be no problem and

Charles would use the test results. Obviously, Charles feels that the test results are so far out of line with

what one would expect from the Brit formulas (which, apparently, have

been shown to be very reliable for matching up with just about every

other German gun's test results) that they are highly suspect.

Then Paul highlights the fact that the 88's velocity can hit 3300 fps,

implying that this is a significant factor that could account for the

difference between test and formula results. Fine. All I'm saying

is that some solid numbers on how this might affect the 88's performance

are going to be needed, to see if they can be plugged into the formula

and thus show the German test results to make sense. I mean, if the

German test results are accurate and were conducted like their tests

of other guns, then there has to be some other factor that can

explain these high penetration numbers. But if this factor can't be

quantified, then Charles is going to have to stick with the most

reliable info. he has, which, in this case, he has deemed to be the

Brit formula.

If this "transitional velocity" component can be accounted for in the

math and be shown to give predictable results, then I would

expect the Brit formula to be ammended to use this factor when velocity

and shell size (if that is an issue, as well) meet the minimum requirements

to necessitate it's use.

[IntelWeenie]

Most of this discussion goes beyond my meager resources, but if the 88/L71 behaves differently than predicted by an equation, how would this be corrected within the game since:

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software:

How do I reach this conclusion? The simple physics behind it. Combat Mission does not use "penetration tables" or charts to determine armor penetration. Instead it uses the mathematical equations described in "Penetration of Armour Plate" originally by (British) Ordnance Board Subcommittee of the Armour Piercing Projectile Committee (reproduced by U.S. Dept. of Commerce National Technical Information Service #PB91127506).

*snip*

Charles

<HR></BLOCKQUOTE>

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

"Belly to belly and everything's better" - Russian proverb

[This message has been edited by IntelWeenie (edited 08-22-2000).]

[PzKpfw 1]

Thought I'd throw in some more British penetration data taken from their wartime estimate: Table V. 7.5cm Ammunition Penetration 90^

The data sheet covers armor penetration , Steel Penetration, & Reinforced Concrete Penetration estimates. Data vs certian types of material vs APCR is not listed & I have suplied what is listed concerning the 7.5cm L/48 & 7.5cm L/70 with APCBC, APCR, & SprGr results. Note the difereing m/s from the earlier examples I posted.

7.5cm KwK.40 L/48

7.5 cm KwK.40 fireing Pzgr.39 APCBC @ 750m/s. Pzgr.40 APCR @ 930m/s in ( )Armor Pentration:

Point Blank - 141mm (176mm)

500m - 128mm (154mm)

1000m - 115mm (133mm)

1500m - 103mm (115mm)

2000m - 92mm (98mm)

2500m - 83mm (83mm)

7.5cm Kwk.40 Fireing Pzgr.39 APCBC @ 750m/s Steel Penetration:

Point Blank - 366mm

500m - 338mm

1000m - 299mm

1500m - 268mm

2000m - 239mm

2500m - 216mm

7.5cm Kwk.40 Fireing Pzgr.39 APCBC @ 750m/s Reinforced Concrete Penetration:

Point Blank - 211mm

500m - 181mm

1000m - 171mm

1500m - 154mm

2000m - 138mm

2500m - 124mm

7.5cm Kwk.40 fireing SprGr.40 @ 550m/s vs Armor:

Point Blank - 52mm

500m - 47mm

1000m - 42mm

1500m - 37mm

2000m - 34mm

2500m - 30mm

7.5cm Kwk.40 fireing SprGr.40 @ 550m/s Steel Penetration:

Point Blank - 135mm

500m - 122mm

1000m - 109mm

1500m - 96mm

2000m - 88mm

2500m - 78mm

7.5cm Kwk.40 fireing SprGr.40 @ 550m/s Reinforced Concrete Penetration:

Point Blank - 78mm

500m - 70mm

1000m - 63mm

1500m - 55mm

2000m - 48mm

2500m - 41mm

7.5cm KwK.42 L/70

7.5cm KwK.42 fireing Pzgr.39 APCBC @ 935m/s. Pzgr.40 APCR @ 1120m/s results in ( )Armor Penetration:

Point Blank - 190mm (212mm)

500m - 160mm (186mm)

1000m - 135mm (160mm)

1500m - 114mm (138mm)

2000m - 98mm (118mm)

2500m - 88mm (100mm)

7.5cm KwK.42 fireing Pzgr.39 APCBC @ 935m/s. Steel Penetration:

Point Blank - 494mm

500m - 416mm

1000m - 351mm

1500m - 296mm

2000m - 255mm

2500m - 229mm

7.5cm KwK.42 fireing Pzgr.39 APCBC @ 935m/s.Reinforced Concrete Penetration:

Point Blank - 285mm

500m - 240mm

1000m - 203mm

1500m - 171mm

2000m - 147mm

2500m - 132mm

7.5cm KwK.42 fireing SprGr.42 @ 700m/s Armor Penetration:

Point Blank - 72mm

500m - 61mm

1000m - 52mm

1500m - 44mm

2000m - 38mm

2500m - 33mm

7.5cm KwK.42 fireing SprGr.42 @ 700m/s Steel Penetration:

Point Blank - 187mm

500m - 159mm

1000m - 135mm

1500m - 114mm

2000m - 99mm

2500m - 86mm

7.5cm KwK.42 fireing SprGr.42 @ 700m/s Reinforced Concrete Penetration:

Point Blank - 109mm

500m - 91mm

1000m - 78mm

1500m - 66mm

2000m - 57mm

2500m - 49mm

Regards, John Waters

---------

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

[This message has been edited by PzKpfw 1 (edited 08-22-2000).]

[Dittohead]

For your own safety thought I might point out that hamster packing is illegal in all 50 states.

[The DesertFox]

Just to complete the picture of 88L/71 APCBC penetration data and to confuse everyone with more data . Here are some more.

First Ian V.Hogg "German Artillery of WW2"

Projectile weight: 10,4 kg

Muzzle Velocity: 1000 m/s

Penetration:

500m : 207mm@0 , 182mm@30

1000m : 190mm@0 , 167mm@30

1500m : 174mm@0 , 174mm@30

2000m : 159mm@0 , 139mm@30

and F.M. von Senger und Etterlin "Die Deutschen Panzer 1926-1945"

Projectile weight: 10,16 kg

Muzzle Velocity: 1000 m/s

Penetration:

0m : 225mm@90 , 198mm@60

457m : 207mm@90 , 182mm@60

915m : 19mm@90 , 167mm@60

1372m : 174mm@90 , 153mm@60

1829m : 159mm@90 , 139mm@60

2286m : 145mm@90 , 127mm@60

If someone is interested to convert the @60 values to @30 values, here´s the table out of Jentz Tiger book:

"As a standard for comparision the effect at 30 degrees angle of impact is set to 100%. Penetration ability at other angles may be estimated from the following table:"

Projectile Type Angle of Impact

PzGr39 (APCBC) 120@0 , 100@30 , 60@45 , 40@60

PzGr40 (APCR) 120@0 , 100@30 , 60@45 , 30@60

Gr HL 105@0 , 100@30 , 80@45 , 50@60

Example: The penetration ability of the 7,5 cm PzGr39 fired from Pak40 at a range of 1000m is 81mm at an angle of impact of 30 degrees. Penetrating ability at this same range a 0 degrees is 95mm, 45degrees is 50mm and 60 degrees is 32mm.

Ugh, I forgot that there are even more data

Ok here it goes:

....and more data:

Bovington Museum, 1975

"Fire and Movement", RAC Tank Museum, Bovington, 1975, pages 22–25. "Penetration v. homogenous armour at 30º, at ranges in yards". The armour is machineable quality.

Weapon Ammo 100 500 1000 1500 2000 2500

88mm L71 APCBC 182 167 153 139 127

....and more

WO 185/194, Tank and anti-tank armament.

A table of "important German SP equipments" gives the following figures for penetration of homogenous armour at 30º with APCBC ammunition:

500 yds 1000 yds

8.8 cm Pak 43/1 (L/71) 184 169

....and more

WO 219/2806, Appendix G to SHAEF/16652/GCT/Arty

Dated 11 July 1944. "Perforation of homo at 30º Strike", ranges in yards.

Weapon Ammo 600 1000 1600 2000

German 88mm KWK 36 (f) APCBC 108 102 94(a) 87

KWK 43 (f) APCBC 178 140 131(a) 121

Notes: (a) Approximate figure (d) Tapered bore (g) A 1945 project

( Fits US 57mm (e) PANTHER gun

© In production but NOT in service (f) TIGER gun

....and some more <G>

WO 291/1407, "The Characteristics of 13 SP Assault Guns."

Penetration in millimetres at normal impact at 1000 yards:

Gun APCBC penetration Special ammo Penetration

8.8cm L71 200 AP40 222

Enjoy

Helge

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

Sbelling chequed wyth MICROSOFT SPELLCHECKER - vorgs grate!

- The DesertFox -

Email: desertfox1891@hotmail.com

WWW: http://www.geocities.com/desertfox1891

[This message has been edited by The DesertFox (edited 08-23-2000).]

[Guest Big Time Software]

John,

The formulae I use from the British report uses Brinnell Hardness as part of the equation, so this is taken into account. I stated this above but I think it bears repeating: Combat Mission does not use any tables or charts or 'penetration test figures' to determine armor penetration. It uses striking velocity, shell mass, caliber, BHN, cap type, and more. Nowhere are test results used directly. The reason being exactly the sort of problem you describe, e.g. Brits using test plate of different BHN than the Germans used, etc. Differing standards mean that one set of figures can't always be directly compared to another.

Note also that Combat Mission also rates many tanks at less than 100% effectiveness for their armor. For example, check out the basic M4 Sherman. Its armor is rated at just 85% - showing the relatively poor quality of the plate. So Combat Mission does take this into account. However this sort of thing would not affect an 88/71 more than, say, an 88/56.

I also stated that I do not doubt Jentz' number' authenticity. I doubt their correctness (or at least their consistency compared to tests for other guns). Those are two different things. In other words, the original test data (if that's where the numbers are from, and I believe they are) are flawed in some way.

<BLOCKQUOTE>quote:</font><HR>Now some of you are saying look at the L/48, L/70 results, according to numerous sources including Jentz the Penetration & m/s data for the German guns & ammunition is clearly wrong. Ie, the KwK.42 at 500ms according to German wartime test data did 124mm using 925m/s Pzgr.39 APCBC vs 300BHN plate.<HR></BLOCKQUOTE>

Except that the L/48 and L/70 numbers I quoted above came from Jentz. So I don't think he thinks they're wrong.

<BLOCKQUOTE>quote:</font><HR>And heres where it gets dicey concerning penetration data as their is speculation the Germans overstated their penetration test results<HR></BLOCKQUOTE>

I didn't say they did this as a matter of practice. I said this is one possible explanation for one gun type - only the 88 L/71. I do not have a problem with any of Jentz' penetration figures for the other German guns. Only the 88 L/71, and the physics tells me that those numbers are dead wrong.

In fact I based my case on Jentz' figures for guns other than the 88 L/71 and clearly demonstrated the inconsistency in the 88 L/71.

<BLOCKQUOTE>quote:</font><HR>What does all this gibberish say, it says that basicly no penetration was exact due to difering conditions, varying plate BHN & quality etc, and that each country came up with differing results on the same guns. <HR></BLOCKQUOTE>

Precisely correct, which is why (I'll say this once again!) Combat Mission does not use any of these figures in its calculations because they are subject to differing standards used by differing countries and cannot be compared directly to one another. Combat Mission uses a model based on physics instead.

Please John, I wish you wouldn't set up a straw man argument like this. Please reread my original post. Nowhere do I state that I think British armor tests are directly comparable to German tests. In fact I believe exactly the opposite to be true. That's why CM doesn't use the figures from those tests. They're just not reliable across the board.

<BLOCKQUOTE>quote:</font><HR>Now I'm curious Charles as their seems to be some major disagrement concerning 12.8cm penetration among some very respected armor historians, while they all use basicly similar 8.8cm L/71 penetration data, what source data did CM use to model the 12.8cm L/55 m/s & penetration<HR></BLOCKQUOTE>

NONE! CM does not use direct source data for armor penetration calculations.

By the way, the fact that several distinguished sources cannot agree on penetration figures for the 128mm (and apparently not even for the 88 L/71 according to Helge's recent post) should be evidence enough that using such a table-based system is a very bad idea and that's why CM doesn't use one.

Paul,

<BLOCKQUOTE>quote:</font><HR>" Transitional Velocity" or "hydro dynamic Transitional Velocity" and its impact on the "plastic wave velocity" of the material and the mode of penetration . Believe me the difference of if penetration is above or below the Transitional velocity is critical!<HR></BLOCKQUOTE>

Please explain why we do not see this phenomenon apparent in the published penetration figures for shells which travel faster than the 88 L/71. Tungsten-based rounds are faster, sometimes much faster (like the one fired from the British 17pdr - 1204 m/s, which is 18% faster than the 88 L/71. Why doesn't the "transitional velocity" effect seem to appear here?).

Helge,

<BLOCKQUOTE>quote:</font><HR>LOL! The test results don´t fit the formula, ergo the test results are wrong ?<HR></BLOCKQUOTE>

No. But it does make them suspect. As we all know, there are many such test results that appear 'strange', because they were conducted with varying standards for BHN test plate, definition of "successful" penetration, etc. Whenever one compares the test figures for one gun to another, especially between nationalities, one must consider that it's a case of "apples and oranges". A direct comparison cannot always be made. When the 88 L/71 figures lie considerably outside the expected range, a warning flag goes up. This does not automatically disqualify the high figures, but it makes them less credible unless additional evidence can be found to support them further. So far I have not seen such evidence in the case of the 88 L/71 except for unsupported comments from people who basically just want it to be better because they think it was an impressive gun. Which it was! Just not impressive to the point of fantasy.

<BLOCKQUOTE>quote:</font><HR>Formulas are a sorry substitute for hard data<HR></BLOCKQUOTE>

Formulas are a sorry substitute for hard data that is consistent. It's consistent data that we need, and it's in very short supply, due to the (sometimes drastic) differences in test conditions mentioned above. "Hard data" is nearly worthless when it's inconsistent. In such a case - and this is the case we have here - formulas based on solid research are much better than inconsistent data. I'm afraid that many WW2 penetration figures fall into the "inconsistent" category. Just look at all the authors and sources in this thread alone that cannot agree on the figures!

<BLOCKQUOTE>quote:</font><HR>Try to compare the 75L/24 with the 75L/70 and see how silly the outcome is.<HR></BLOCKQUOTE>

I haven't done this yet but I don't know why you would want to. This is a silly example because the 75 L/24 is a very low-velocity gun. I chose the 75/48 and 75/70 in my example because they, like the 88's, are high-velocity guns. I also stated quite clearly that one should not expect linear results. So making a case based on a low-velocity gun is probably going to give worthless results. I never said it would be any other way.

<BLOCKQUOTE>quote:</font><HR>BTW: If you use the very rough formula at David Honners site you have to use the velocity of the shell in the moment of IMPACT and NOT the muzzle velocity. <HR></BLOCKQUOTE>

This is called 'striking velocity' and it is, indeed, what Combat Mission uses. Again, in my previous example I wasn't trying to provide precise penetration data. I showed that the 88/71 figures are not even close to what they should be. Even rough approximations are sufficient to demonstrate this quite clearly.

Lee,

<BLOCKQUOTE>quote:</font><HR>The whole point here is that the test results themselves have been questioned as to whether they are indeed "facts"...Obviously, Charles feels that the test results are so far out of line with what one would expect from the Brit formulas (which, apparently, have been shown to be very reliable for matching up with just about every other German gun's test results) that they are highly suspect.<HR></BLOCKQUOTE>

Thank you Lee, that succinctly states the point I have been trying to make.

Charles

[Guest Big Time Software]

Cripes! How hard is this to understand? The test data is NOT reliable because it is not conducted under the same laboratory conditions. ANYBODY with even highschool level education should understand that you can't compare scientific data that is not grounded in the same methodology. This is as true for armor penetration as it is economic figures.

OK folks... here is my "hard data" I just came up with. I decided to shoot my M1 Carbine at 50m today. I cracked off about 25 rounds. Here is the "hard data" that everybody should base all their knowledge on about the M1 Carbine:

1. Chances of hitting a 12x12 inch piece of paper at 50m is about 78%

2. Chances of hitting the center of such a piece of paper is less than 1%

3. The gun will jam after about the 23 shot and cease to fire thereafter due to the firing pin wearing out.

Conclusions... the M1 Carbine is inherently inaccurate and is only good for about 20+ shots before it breaks.

Or it could be that my gun wasn't sighted in and that after a couple thousand rounds fired through this by veterans of probably 2 wars it is plum worn out.

Yes, this is a rather silly example, but people are being excessively silly here besides me

Steve

[The DesertFox]

Might be some of you haven´t noticed, but the values CM chooses right now, do pretty much fit with the values of the 1975 Bovington report I quoted above.

______CM_____Jentz_____Hogg____Bovington´75____WO185____WO219

range

100m 177mm 202mm

500m 165mm 185mm 182mm 167mm 184mm 178mm

1000m 151mm 165mm 167mm 153mm 169mm 140mm

2000m 121mm 132mm 139mm 139mm 121mm

Talk about coincidence.

And things are REALLY starting to get interesting if we compare the figures of this Bovington´75 report with the Jentz figures for the 75L/70

______Bovington´75_____Jentz

range

500m 141@30 124@30

1000m 121@30 111@30

1500m 104@30 99@30

2000m 89@30 89@30

Any ideas ?

Helge

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

Sbelling chequed wyth MICROSOFT SPELLCHECKER - vorgs grate!

- The DesertFox -

Email: desertfox1891@hotmail.com

WWW: http://www.geocities.com/desertfox1891

[This message has been edited by The DesertFox (edited 08-23-2000).]

[Paul Lakowski]

The idea of dismissing test data cause they don't quite match up is wrong.Ballistic researchers use test data all the time its called 'normalizing the data to a single reference point'. Thats why they need to know plate hardness , lateral confinement and depth confinement etc for each test.

But you'll find that they all treat test data as king to determine if there sim works or not.If they it doesn't they go back to the drawing board.

Transitional velocity comes into all penetration of all projectiles its just a question of what striking velocity.

[PzKpfw 1]

Charles, thx for the reply. I think you may have misunderstood some part of my post the below will hopefully clear this up .

I am not trying to set up any straw argument Charles, (I don't do that type of thing) I was trying to explain some on the diferences in wartime penetration data results thru useing rare actual British vs German examples, to the forum, as I thought some would find the data interesting & or useful.

As it highlighted the diferences that could be achieved useing the same ammunition by 2 different nations, vs differing plate BHN as well as the differing muzzle velocity numbers, and the resistance differences between German & Allied armor plate.

The German test plate used in the tests was 121 - 150mm thickness @ 235 - 265BHN plate, or 81 - 120mm thickness @ 279 - 309BHN. The standard most used has been 300BHN comparisons.

Charles, I didn't mean to imply you questioned all German test results; I was pointing out that its been whispered for years that the German's may have doctored their penetration data, ever since an document was allegedly dug up from Krupp dated 1944 that allegedly said something to the effect, only the best ammo was used, and numbers were doctored etc, its still whispered but unsubstantiated.

I know you pointed out the data wasn't Jentz's but if you read your post over a few times you will see that one could get the impression that Jentz's name sticks out quite clearly, concerning the data & a false assumption could be made the post's comments on penetration concern his work if read the wrong way.

So I took the liberty of adding that the figures were not Jentz's in my post so their would be no mistake, L8r on as did Helge. I don't think anyone here wants someone contacting Tom Jentz and giveing him the false impression from reading your post wrong that you were questioning his credibility.

But as CM doesnt use any actual penetration data from the WWII tests this whole thread is realy moot as it is based on the 8.8cm L/71 Waffenamt test data & it doesnt apply to CM, as it doesnt base penetration results on any of the test data.

Ok enough on that I'll let the experten settle whether or not 8.8cm L/71 could do its stated panetration . I told you I'm not a mathemitician I need things in simple black & white so the 12.8cm L/55 pen figures in the game were extracted from useing the formula in the 1950 report? & I can use them as extracted pen data for the L/55?.

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 08-23-2000).]

[PzKpfw 1]

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

Transitional velocity comes into all penetration of all projectiles its just a question of what striking velocity.<HR></BLOCKQUOTE>

I have a question was the transitional velocity effect on projectiles traveling over 2800m/s even known about in 1950?.

As Robert pointed out IIRC the error in the British report concerning slope/angle equasions was because they hadn't discovered an efect at that time that was later discovered. The report was based on all they knew about penetration to that date.

Regards, John Waters

---------

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

[This message has been edited by PzKpfw 1 (edited 08-23-2000).]

[Paul Lakowski]

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

I have a question was the transitional velocity effect on projectiles traveling over 2800m/s even known about in 1950?.

As Robert pointed out IIRC the error in the British report concerning slope/angle equasions was because they hadn't discovered an efect at that time that was later discovered. The report was based on all they knew about penetration to that date.

<HR></BLOCKQUOTE>

John the answer is yes and no. They new that something was happening but not exactly what. You have to remember most stuff back then was done by trial and error, initially the idea of APDS was rejected on the grounds as being 'unproven and too complex'.

Most work that covers the transition from plugging type penetration to erosion penetration was done with APDS tech after the war.

The works that I'm looking at now is late 60s early 70s and alot of it was done in Canada.

[Guest Big Time Software]

Paul,

<BLOCKQUOTE>quote:</font><HR>Ballistic researchers use test data all the time its called 'normalizing the data to a single reference point'. Thats why they need to know plate hardness , lateral confinement and depth confinement etc for each test.<HR></BLOCKQUOTE>

Exactly. And because I don't have fully credible and complete sources for this information for all (or even most) guns in the game, the test data simply cannot be fully trusted.

It's a good rough guide, but that's the best it can be short of having complete, reliable, and consistent information about the methodologes used in all tests. It's a shame, but we just don't have it.

<BLOCKQUOTE>quote:</font><HR>The works that I'm looking at now is late 60s early 70s and alot of it was done in Canada.<HR></BLOCKQUOTE>

What work is that? I'm interested in getting a copy.

John,

<BLOCKQUOTE>quote:</font><HR>Charles, I didn't mean to imply you questioned all German test results; I was pointing out that its been whispered for years that the German's may have doctored their penetration data, ever since an document was allegedly dug up from Krupp dated 1944 that allegedly said something to the effect, only the best ammo was used, and numbers were doctored etc, its still whispered but unsubstantiated. <HR></BLOCKQUOTE>

OK, thanks for clearing that up.

<BLOCKQUOTE>quote:</font><HR>I don't think anyone here wants someone contacting Tom Jentz and giveing him the false impression from reading your post wrong that you were questioning his credibility. <HR></BLOCKQUOTE>

Quite right. Jentz would certainly not be the first person to unwittingly use a bit of wrong data that seemed right, or that came from a seemingly credible source but turned out to be wrong anyway. Sheesh, we've done our share of that in CM. ("Whaddaya mean there's smoke/WP for a 60mm mortar! It says right here that-- er... whoops, heh heh. OK, there it is." )

<BLOCKQUOTE>quote:</font><HR>so the 12.8cm L/55 pen figures in the game were extracted from useing the formula in the 1950 report? & I can use them as extracted pen data for the L/55?.<HR></BLOCKQUOTE>

Correct.

<BLOCKQUOTE>quote:</font><HR>I have a question was the transitional velocity effect on projectiles traveling over 2800m/s even known about in 1950?<HR></BLOCKQUOTE>

I believe you mean 2800 ft/sec. In WW2, all Allied APCR/APDS/SVDS/HVAP rounds traveled well above this speed.

I'm not saying that a high-speed effect doesn't exist, but simply that there are other German rounds (e.g. 75 L/70) that are very nearly as fast as the 88 L/71, and yet they fit in almost perfectly with the equations that CM uses. The 88 L/71 is only about 10% faster than the 75 L/70, and yet you guys are suggesting that this mere 10% suddenly transforms the whole penetration process dramatically. I'm sorry but I just don't buy it. I'm going to have to see some very credible and convincing evidence before I do.

I could accept a small 'boost' for the 88 L/71, but your comments along with Jentz' numbers suggest a 10-15% 'transitional velocity' bonus, whereas a gun nearly as fast, the 75 L/70, gets no measurable bonus whatsoever. I also don't see any such bonus for tungsten-based shells which are faster than the 88 L/71 (i.e. their physics works out using CM's current algorithms). Why just the 88 L/71, whose speed is in the middle of this group? It all just doesn't make sense.

The 88 L/71 was a great gun. But so were the 75 L/70 and Allied tungsten-based weapons. And even the 88 L/56 and 75 L/48 were good. The differences in the published test data simply aren't borne out by the physics.

Charles

[This message has been edited by Big Time Software (edited 08-23-2000).]

[willys]

Charles, (or whomever else can answer)

In your replies about 88/L71 data you mentioned WP ammo for mortars. Since I don't have the full game version, is WP modeled (for tanks) in CM? How about canister rounds? I know that canister is used in CC3 but, honestly, I have only seen the game fire it about twice. When it did I was pretty confused about what was going on until I remembered about these rounds.

[Paul Lakowski]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software:

Paul,

And because I don't have fully credible and complete sources for this information for all (or even most) guns in the game, the test data simply cannot be fully trusted.

<HR></BLOCKQUOTE>

Why? Since when was formula data more reliable than test data?

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

I'm not saying that a high-speed effect doesn't exist, but simply that there are other German rounds (e.g. 75 L/70) that are very nearly as fast as the 88 L/71, and yet they fit in almost perfectly with the equations that CM uses. The 88 L/71 is only about 10% faster than the 75 L/70, and yet you guys are suggesting that this mere 10% suddenly transforms the whole penetration process dramatically. I'm sorry but I just don't buy it. I'm going to have to see some very credible and convincing evidence before I do.

<HR></BLOCKQUOTE>

Thats cause you guys are looking in the wrong direction.Penetration is linked to projectile lenght not diameter, thats why no one uses these formulas any more.I've just finished working through the 2Lb & 17Lb APDS and German 75L24 , L48 & L70 APCBC ammo as well as the 88 Flak 18 & L71 APCBC ammo using projectile lenght , L/d value , ratio of tip to body diameter and tip hardness, and MV... and got within a few mm of the published vertical penetration data for 0-100m range.By using the empirical test results.

This is far from conclusive and I'll have to do some more work to see if I can find more results to compare.

[Guest Big Time Software]

<BLOCKQUOTE>quote:</font><HR>Why? Since when was formula data more reliable than test data?<HR></BLOCKQUOTE>

Since when do you believe, without question, that something stated as "fact" can not be wrong, even if it doesn't make sense or jibe with other data? Simple logic here...

Our equations are based on sound, constant physics. Even if all of our results are wrong they are one thing -> quantifiably consistant.

The thing that you are dodging is the most basic principle of scientific research. And that is when you find something that doesn't fit you question it. Don't rule it out of hand, but question it. You refuse to do this, and therefore would make a poor scientist.

The fact is that our euquations produce results that DO match the test results of nearly every weapon EXCEPT FOR ONE. Right away you should be questionging the little bit of test data that is different to see WHY it is different. You can choose to rule the equations are in error, with no evididence other than the test data in your corner, but that is poor science. The more obvious reason for the difference is that the data is wrong. There even seems to be evidence from Krupp that they fudged the data, yet you still seem to think that our equations are wrong. You also haven't responded to any of the scientific logic that Charles has laid out very methodically. Again, this is poor science.

Sorry, we do not back down from scientific simulation because someone has it in their head that a few typed letters of ink can not be questioned. Everything is up for questioning, including our formulas. But when there is an obvious and fairly strong case to be made that the data is wrong, people need to accept it or refute it with a stronger case than "it says so therefore it is true".

Steve

[PzKpfw 1]

Lets not let this very interesting & important discussion degenerate into an pissing contest, on who's a better scientist etc. I think everyone here just wants the truth resolved on the pen test data.

I dont think either Steve or Paul even know one another enough to be makeing snap judgements on each others professional abilities, and I would think the quality of posts would speak for themselves, for both.

This discussion started because BTS chose to ignore primary source material concerning the 8.8cm L/71 penetration publicly announce they felt the data was flawed. of course a statement like that is going to generate a very detailed, & at times heated discussion, as CM is touted 'realistic', while challengeing historical documentation.

Charles has basicly stated his case on why he feels the penetration is wrong & justifying BTS's numbers with physics, does that mean we are not to discuss this anymore? if so please say so, or lock the thread.

The burden of prooveing that the 50yr old 8.8cm L/71 German wartime test data is valid has been laid on ppl who disagree or don't know who is correct.

Maybe this should be taken E-mail or just dropped it altogether unresolved. But it is a very important subject to the ppl in the ballistic community as it openly challenges an historical given. the question of the 8.8cm L71 Penetration is going to reapear anytime someone checks CM Pen data vs German wartime data.

Regards, John Waters

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People who can smile when things go wrong

have found someone else to blame.

[This message has been edited by PzKpfw 1 (edited 08-23-2000).]

[Guest Big Time Software]

willys,

CM doesn't model WP right now, but it's under consideration for the future.

Paul,

<BLOCKQUOTE>quote:</font><HR>Why? Since when was formula data more reliable than test data?<HR></BLOCKQUOTE>

When the formulae are based on consistent testing standards and the other test data clearly are not. How many times do I have to say this?

If you believe that the penetration test data can simply be accepted at face value, and choose to ignore the greatly varying standards for test plate type, hardness, and quality; definition of "successful" penetration; national differences; selective choice of nonrepresentative ammunition quality; and even potential for outright propaganda-influenced deception, then I think you are gravely mistaken.

<BLOCKQUOTE>quote:</font><HR>Penetration is linked to projectile lenght not diameter<HR></BLOCKQUOTE>

Incorrect. Penetration is proportional to mass, which correlates with projectile length. And I didn't say anything about diameter, so I don't know who you're responding to about that. Penetration is inversely proportional to diameter, all else being equal.

Charles

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software:

I believe you mean 2800 ft/sec. In WW2, all Allied APCR/APDS/SVDS/HVAP rounds traveled well above this speed.

<HR></BLOCKQUOTE>

Yes Charles me bad . To much looking at German m/s data

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

I'm not saying that a high-speed effect doesn't exist, but simply that there are other German rounds (e.g. 75 L/70) that are very nearly as fast as the 88 L/71, and yet they fit in almost perfectly with the equations that CM uses. The 88 L/71 is only about 10% faster than the 75 L/70, and yet you guys are suggesting that this mere 10% suddenly transforms the whole penetration process dramatically. I'm sorry but I just don't buy it. I'm going to have to see some very credible and convincing evidence before I do.

<HR></BLOCKQUOTE>

Understood Charles I do see your reasdoning but want to add its not an 'we' are sugesting I asked if transitional velocity was even known about in 1950 as ballistic research from what I understand has evolved way past what was known in 1950 and errors were found in the original findings, leading to new formula results etc.

Could all data concerning 3000fps penetrators be flawed from that time, because of this transitional velocity, and I'm not saying the 8.8cm penetration is suposed to leap to the test results because of it I'm trying to learn something .

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 08-23-2000).]

[Magnus]

Wow ! Anybody ever seen another forum with such serious and intelligent debates ?

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

Venez visiter le seul site consacré à Combat Mission en français : Appui-feu http://appui-feu.panzershark.com

[This message has been edited by Magnus (edited 08-23-2000).]

[Paul Lakowski]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software:

Incorrect. Penetration is proportional to mass, which correlates with projectile length. And I didn't say anything about diameter, so I don't know who you're responding to about that. Penetration is inversely proportional to diameter, all else being equal.

Charles<HR></BLOCKQUOTE>

Penetration is proportional to mass , is it ? Thats why in Brooks tests three projectiles of the same dimentions [ 4.5 :1 L/d ogive penetrator with 0.35 “ x 1.71” dimentions ] made of Tungsten carbide [ 14.7 g/cm³] , Tungsten Alloy [ 17.3 g/cm³] and Uranium alloy[18.5 g/cm³]. All the projectiles where fired from the same gun at the same target [ Type 4340 - Rc 30-32] over striking velocity of 2000 f/s upto 4500 ft/s. If penetration was propotional to mass the heaviest should

have penetrated the most,heres the results...

<PRE>

Tungsten carbide[Rc 74]

1840 ft/s = 0.8”

2264 ft/s = 1.73 “

2639 ft/s = 2.05”

3017 ft/s = 2.52”

3367 ft/s = 2.97”

3721 ft/s = 3.42”

4405 ft/s = 4.41”

Tungsten Alloy[Rc 31]

1862 ft/s = 1.34 “

2600 ft/s = 1.4“

3322 ft/s = 2.07”

4024 ft/s = 2.28”

4301 ft/s = 1.67”

4619 ft/s = 1.93”

Uranium alloy[Rc 50]

2125 ft/s = 0.47”

2503 ft/s = 0.94”

2903 ft/s = 1.91”

3236 ft/s = 1.85”

3584 ft/s = 1.83”

3914 ft/s = 1.81”

4484 ft/s = 1.93”

Steel [ Rc 60]

1940 ft/s = 0.89”

2717 ft/s = 1.46”

3053 ft/s = 1.63”

</PRE>

In all velocities the lighter WC projectile out penetrates the heavier WHA and U²Mo projectiles , while the ultra light

steel projectile matches the penetration of both the heavier WHA and U²Mo alloys at ~ 2700 ft/s . Note how increasing velocities doesn’t always generate increasing penetration. From Brooks other work at 2700 ft/s that vary the projectile tip diameter the WHA penetration changes as follows.....[ test conditions exactly as above].

<PRE>

0.0001 = 1.5 “

0.002 = 1.8”

0.1 = 1.78”

0.2 = 1.6”

0.35 = 1.1”

0.5 = 0.9”

0.35 with WC tip = 1.7”

</PRE>

Reality is never as simple as a formula, and the 'balls in your court' to prove that the 88L71 penetration data is wrong ,cause its been doctored.

[This message has been edited by Paul Lakowski (edited 08-23-2000).]

[Simon Fox]

I have read this thread with interest though I freely admit to having little actual interest in the technical aspects of armour penetration. As a scientist I have been more interested in the nature of the debate. I have to say that I agree with Charles and Steve that those questioning the predictions lack scientific rigour in some of their arguments.

<BLOCKQUOTE>quote:</font><HR>The thing that you are dodging is the most basic principle of scientific research.<HR></BLOCKQUOTE>

Exactly. It may be that those questioning the CM data are correct and that the formulae used in CM though largely accurate does not account for all eventualities and that it has been supplanted somewhat by more modern methodologies. However, this has not been satisfactorily shown and that means not just quoting conflicting data but properly citing the source and methodology used to obtain it as well as giving an argument as to why it is so.

To summarise:

(1) There is an empirically derived formulae which fairly accurately predicts the vast majority of experimental data.

(2) The experimental data for one series of experiments conflicts with the results predicted by the formulae.

Lakowski, Waters et al in their arguments cite data from the review publications by Jentz and Hogg among others to support their hypothesis that the formulae does not adequately model the 88L71 gun performance. They fail to cite the primary sources for this data. Nor do they cite the actual methodology used to perform the tests including the experimental design and the materials. Furthermore since they do not cite the primary source for the data it is impossible to properly judge the scientific credibility and integrity of the individuals and/or organisation which originally published the data. Since it appears that no other comparable data is available for this gun (?) and it is clearly impossible to repeat these experiments I beleive that they have provided insufficient argument to support their hypothesis. It may be that they are correct to question the validity of the formulae used. However, as it now stands it accurately predicts all of the properly documented experimental data. I would hope they can provide further evidence to support their argument.

<BLOCKQUOTE>quote:</font><HR>Reality is never as simple as a formula, and the 'balls in your court' to prove that the 88L71 penetration data is wrong ,cause its been doctored.<HR></BLOCKQUOTE>

Well actually a lot of reality is fairly accurately predicted by formulae and quite a lot of the rest of it can be closely approximated. The ball is really in your court to support the integrity of the data you cite and mount an argument as to why it deviates from those the formulae predicted.

<BLOCKQUOTE>quote:</font><HR>The burden of prooveing (sic) that the 50yr old 8.8cm L/71 German wartime test data is valid has been laid on ppl who disagree or don't know who is correct.<HR></BLOCKQUOTE>

Exactly

[This message has been edited by Simon Fox (edited 08-23-2000).]

[Guest Big Time Software]

Paul,

<BLOCKQUOTE>quote:</font><HR>Penetration is proportional to mass , is it ? Thats why in Brooks tests three projectiles of the same dimentions [ 4.5 :1 L/d ogive penetrator with 0.35 “ x 1.71” dimentions ] made of Tungsten carbide [ 14.7 g/cm3] , Tungsten Alloy [ 17.3 g/cm3] and Uranium alloy[18.5 g/cm3]<HR></BLOCKQUOTE>

Yes, penetration is proportional to mass, all else being equal. That's the key, Paul - all else being equal. Your example introduces a second variable - projectiles made of different metals! Of course this will change things! Certainly some materials are better than others for use in projectiles. I never said otherwise, and so your introduction of the issue into the debate is quite puzzling. It has absolutely nothing whatsoever to do with whether projectile length or mass is the critical factor.

Let us also remember that the standard APCBC projectile from the 88 L/71 is made from the same stuff as that from an 88 L/56. No special behaviors here.

Length of projectile is related to penetrative power only indirectly. Mass is directly related to penetrative power for the following reason: penetration is maximized by placing the greatest amount force against the smallest possible area of armor to be penetrated. Because it's important to minimize the area of contact in order to maximize penetration, it's usually good to use a "thin" (i.e. small caliber/diameter) projectile.

But if we make the projectile "thin", that reduces its mass, which reduces the penetration. So we have to counterbalance this. There are at least two ways to do this. One way is to make the projectile longer. This keeps the diameter small but increases projectile mass and therefore its force. In this way the length of the projectile is indirectly related to penetrative power. Another way is to increase the density of the projectile's material. This also increases mass, and therefore force, but also does not increase diameter. This is why modern projectiles are often made of heavy metals, like depeleted uranium.

Incidentally a small diameter and high mass usually mean better aerodynamics, which preserves energy and means greater striking velocity as well. A long projectile accomplishes this. So does a denser one. A longer and denser projectile is even better.

<BLOCKQUOTE>quote:</font><HR>Reality is never as simple as a formula, and the 'balls in your court' to prove that the 88L71 penetration data is wrong ,cause its been doctored.<HR></BLOCKQUOTE>

Sorry Paul, you can't get off the hook that easily. You have provided no evidence whatsoever that the 88 L/71 data should be believed. And if you look above in the thread, at Helge's numbers, you'll see that even the published sources do not agree with one another. If you are so set on me accepting the published numbers, which set should I take? The Bovington numbers? Jentz' numbers? How about WO219? Another one? Funny how they're all different, isn't it? They don't agree even with one another, and didn't long before CM came on the scene. And yet you imply that they are all somehow correct.

It's impossible, Paul.

Ball's in your court now.

Charles

[This message has been edited by Big Time Software (edited 08-24-2000).]

[Guest Big Time Software]

Thanks Simon for that viewpoint.

The fact is that if our equations are incorrect, based on the 88L/71 data, then logically the equations should be wrong for any other weapon that has similar characteristics. In other words, if we missed a variable/formula having to do with velocity then it would be impossible for the data to come out correctly for the other weapons of similar velocity. The fact that everything else BUT the 88L/71 checks out, should settle the matter.

And that is why when there is one oddball, with many unknowns about its true value, attention should be focused on the oddball NOT the equation that uncovered it. It is sorta an all or nothing situation in some respects.

As a historian I can tell you for a fact that there are plenty of errors and/or conflicting data in historical documentation of weapons. See how many different rates of fire you can find for the MP44 for example. Simple measurement, same weapon, different "official" results. WWII is particullarly full of conflicting data. The Germans might have even conducted tests consistant with all their other ones, but simply fudged the numbers for propaganda or contract reasons. The latter is not far fetched, nor is it "paranoid". Military contractors have a long history of lying to the one footing the bill Having known someone who worked on the ill fated Sgt York project (US radar controlled mobile AAA) I can say for sure this happens

Anyhoo... again the burdon of proof rests on those doubting our equations. If someone can come up with a set of equations that can come up with results, consistantly inline with test firings including the 88L/71, then we will eat our words without salt or pepper Until that time, it should be assumed that we have confirmed that a somewhat questionable set of test data (others have questioned it you know...) is indeed incorrect for one reason or another.

Steve