Thick British AFV Armour

[rexford]

During previous research, we obtained a metallurgical analysis of British armor which suggested that the armor did not adequately harden above 2.5" thickness, and would lose resistance.

We also analyzed the British NPL (National Physics Laboratory) equation which summarized firing test results as a function of armor thickness, hardness, angle, etc.

When German and American high hardness armor was attacked by overmatching rounds (T/D<1), the armor lost some resistance but was still useful. When British high hardness was overmatched, resistance dissolved to almost zero.

One of the analyses suggested that 152mm British armor was equivalent to about 139mm of good quality American test plate, based on comparison of penetration data for 75L48 APCBC.

Should thick British armor (over 2.5") be penalized a bit more in CM, with greater reductions in quality as the thickness goes up? So actual quality reduction would be a function of thickness and would vary over the different sections of a tank, instead of appying a single modifier for entire tank.

We are looking for the source of metallurgical and firing tests, and will provide shortly. Alot of the stuff is in my storage shed somewhere, or is in other people's files (somewhere).

On a related topic, Mark Diehl published a series of articles in AFV G2 that included German projectile details and penetration data. This info is published for PzKpfw IV on Will Phelps's PzKpfw IV web site, and Phelps interviewed Mark Diehl during his presentation of Diehl's work.

The penetration data provided by Diehl appears to be based on allied tests of German ammo, and exceeds CM figures by a tidy lot.

141mm penetration for 75L48 APCBC at 750 m/s velocity and 0m, about 190mm for 75L70 APCBC at 0m.

Diehl's figures for 75mm ammo may be the best figures available for German APC and APCBC, and exceed CM penetration. We looked at the data for 75mm's and it appears to be a DeMarre equation from one gun performance to others, which would be a function of velocity if rounds are 75mm and weigh the same (penetration proportional to velocity raised to 1.4283 power).

DeMarre equation works well with U.S. test data in TM-9-1907 and appears to also apply to German ammo.

We are not saying that Diehl's data for 88L56 and 88L71 and others is the ultimate, but his 75mm stuff is the best we've seen. We will re-examine the 88 predictions and see how it looks.

Finally, why does CM penetration for U.S. 75L40 APCBC exceed TM-9-1907 by so much? TM has 91mm penetration at 0m and 0°, and since so much has been made about U.S. ammo factories and inconsistent quality, how can CM predictions for 75L40 APCBC EXCEED pen. tests using best quality ammo?

Inquiring minds want to know.

[:USERNAME:]

I hate to get involved in another case from the reXford files (the truth is out there.. in my shed.. get in now scully!..) but...

I dont believe the AP round for the 75mmL24 is the same as the 75mmL46, L48, L43 and L70. I am not putting you on. Look at the data closely:

http://ourworld.compuserve.com/homepages/willphelps/Specs-03.htm

I believe that the HE is the same at least for the 75mm L24, 75mm L43/48 and perhaps the panther (not covered here anyway) but there might be a difference in AP. I have drawings of them and there does appear to be some difference.

Dont mention it..

Lewis

[rexford]

The British National Physics Lab (NPL)penetration equation was used to predict 17 pounder velocities needed to penetrate 60mm, 76mm, 100mm and 150mm British plate at 0° impact. Results were then compared to DeMarre equation from 60mm, assuming that 60mm had Quality of 1.00.

We assumed that all plate had 250 Brinell Hardness, since we do not have access to British hardness-vs-thickness data for later war armor. If anyone has this data and can share it it would be appreciated.

A velocity of 1292 fps is needed to defeat 60mm, based on NPL equation. Assume 60mm quality factor is 1.00.

Against 76mm plate, 1474 fps is predicted NPL velocity for penetration. DeMarre from 60mm predicts 72.4mm at 1.00 quality, quality factor is 0.95.

When 100mm plate was attacked, NPL impact velocity is 1747 fps. DeMarre from 60mm penetration predicts that 1747 fps penetrates 92mm of 1.00 Quality plate, so quality factor is 0.92.

When 150mm plate was attacked NPL velocity is 2316 fps. DeMarre from 60mm penetration predicts that 138mm of 1.00 Quality plate should be penetrated at 2316 fps. So 150mm quality is 138/150, or 0.92.

CM factor for Churchill armor resistance is close to predictions from NPL/DeMarre equations, and is remarkably close to our finding that 152mm British resisted German penetration like 139mm in tests, which was arrived before we received NPL equation.

CM uses 0.95 multiplier for Churchill 7, we would suggest 0.92 for 152mm armor and sliding scale for other British thicknesses (and tanks). Just to be precise in our estimates.

And it would be good to use higher German penetration figures as depicted in Diehl's work, just to be in line with the best available info that is out there. With Diehl's permission, of course.

A good discussion of NPL equation is contained in Hal Hock's AFV NEWS article, THE PITCHER AND THE STONE, and the British report PENETRATION OF ARMOUR PLATE.

As noted in the preceding post, British high hardness armor lost resistance quickly when overmatched (T/d<1) and hit at an angle.

Analysis of PzKpfw IVE high hardness armor showed that German armor was 10% more resistant against 2 pounder AP than British machineable armor, and more resistant than British high hardness. NPL equation shows that positive armor hardness effects are more pronounced against small projectiles, and decrease rapidly as ammo diameter increases.

We read an account of British high hardness armor, used on light tanks bound for Africa, where residual stresses in the plate caused all of the tanks to split open in the warehouse. When armor is heat treated and hardened, it may shrink as it cools which can produce stresses. Heat treatment should address this.

Every country had some problems with armor quality.

[rexford]

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

[Dittohead]

I assume that this would affect the churchchill only.

[This message has been edited by Dittohead (edited 01-28-2001).]

[Paul Lakowski]

Originally posted by :USERNAME::

I hate to get involved in another case from the reXford files (the truth is out there.. in my shed.. get in now scully!..) but...

I dont believe the AP round for the 75mmL24 is the same as the 75mmL46, L48, L43 and L70. I am not putting you on. Look at the data closely:

http://ourworld.compuserve.com/homepages/willphelps/Specs-03.htm

I believe that the HE is the same at least for the 75mm L24, 75mm L43/48 and perhaps the panther (not covered here anyway) but there might be a difference in AP. I have drawings of them and there does appear to be some difference.

Dont mention it..

Lewis

I've seen pics of these rounds and the penetrators look the same. I always assume the K Gr rot Pz was APC , as opposed to the PzGr 39 , which is APCBC. I don't see the difference other than a bursting charge comp.

[:USERNAME:]

READ CLOSELY THE WEBSITE!!!

It claims that the 75mmL24 fired K Gr rot Pz (was APC) and Pzgr. (Kw. K. 38). This is NOT Pzgr 39!! My cutaway drawings show that this "38" round appears to have a large HE cavity in it and the websites data backs this up.

Sorry. I take my german ammunition a bit serious.

Pzgr. (Kw. K. 38)

?

TNT

1.33 kg.

90% PETN

Bd. Z. F. 7.5 cm. Pz. gr.

black

-

Pzgr. 39 FES

APCBC

RDX

83 gm.

90% PETN

Bd. Z. 5103

black w/red marking

-

Pzgr. 39 Kw. K. 40

APCBC

Cyclonite

82 gm.

90% PETN

Bd. Z. 5103

black w/red band/marking

Lewis

[This message has been edited by :USERNAME: (edited 01-28-2001).]

[This message has been edited by :USERNAME: (edited 01-28-2001).]

[Bullethead]

I think Rexford must have gotten hold of some bad data. Either in the form of an isolated result from a bad batch of plate, or simply some human mistake in interpreting the results.

The idea that the Brits couldn't make decent armor plate over 2.5" thick is ridiculous. As you might be aware, naval armor plate is often MUCH thicker than this, and at the time of WW2, the Brits made the best naval armor plate in the world (and thus of all time). Thus, given that naval armor and tank armor are designed to do exactly the same job, are made of the same materials, are fabricated using the same processes, and are often made by the same firms, I find it extremely difficult to accept that Brit naval armor expertise did not find its way into tank armor fabrication.

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

-Bullethead

In wine there is wisdom, in beer there is strength, in water there is bacteria.

[This message has been edited by Bullethead (edited 01-28-2001).]

[:USERNAME:]

Originally posted by Bullethead:

I think Rexford must have gotten hold of some bad data. Either in the form of an isolated result from a bad batch of plate, or simply some human mistake in interpreting the results.

No. He , they, all them we's, have tested all plates and he has them in his shed.

He has never made a mistake ever. Never ever. Certainly not in the "accuracy" thread (Is the irony lost on anyone that read that thread? Its an accuracy thread and the shed-archives commandant made on average one boner mistake per page of that thread? Eh. maybe its just me..)

Ever heard of dyslexia? rexforia? lewisite?

I am going to bed.

Lewis

[Ksak]

Can anybody say "anal"?

[M. Bates]

Originally posted by Ksak:

Can anybody say "anal"?

Anal.

Seriously Ksak, surely these guys are furthering our knowledge?

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

Rugged Defense England Team Website:

http://combatmission.portland.co.uk

For all our AARs

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

"I drive over farmyard animals in my farmyard tractor, then I laugh afterwards."--CavScout [comp.sys.ibm.pc.games.war-historical]

[rexford]

The intent of the posts was to provide some back-up for 0.95 quality modifier for Churchills and other British tanks.

Suggestions based on analysis of armor from different companies in UK, during WW II.

Conclusion limited to tank armor. U.S. tank armor industry put out some deficient plates and cast while navy got the alloys and built good thick armor.

Tanks and ships had different priorities.

I put together the original equations and curves for flaws, which is basis of 0.85 modifier for Shermans and Panther glacis and others. British armor study is just another piece.

How valid is it all?

Panther glacis and Sherman penetration resistance problems are supported by alot of stories. We don't have much familiarity with actual resistance of British armor to German hits, and put out the posts trying to see what responses we obtained.

Comments welcome.

[PeterNZer]

I value your posts Rexford, always informative and full of good detail. Pitty Username has to get so excited.

PeterNZ

[PzKpfw 1]

Originally posted by Bullethead:

I think Rexford must have gotten hold of some bad data. Either in the form of an isolated result from a bad batch of plate, or simply some human mistake in interpreting the results.

Actualy Bullet Rex is dead on, I have been posting the AQ problem with the CH armor for months now & been ignored here, the British tank armor industry was in bad shape during the CH production, believe it or not due to lack of QC, isilation of plants, lax standards, etc. So 152mm resists the equivelent of 130's US plate & needs to be adjusted in CM to reflect the AQ.

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

"We've got the finest tanks in the world. We just love to see the

German Royal Tiger come up on the field".

Lt.Gen. George S. Patton, Jr. February 1945.

[Jeff Duquette]

From: David Honner's Guns vs. Armour

http://www.wargamer.org/GvA/background/armourtypes6.html

Flaws in Armour

To complicate things even further, some armour plates and castings were flawed which significantly affected their ballistic resistance. The only way to determine the presence or absence of flaws is to sample the steel in question and run metallurgical tests. By deduction, premature ballistic failure as recorded in field tests indicate the presence of flaws, such as the several tests of captured Panthers which had poor quality glacis plates (which includes the report of tests of Soviet 100mm and 122mm guns against a captured Panther at the Kubinka Proving Ground).

British and USA armour before 1944 was badly flawed.

It was determined reliably that a large proportion of USA armour, both cast and rolled, produced prior to November 1943 was flawed to such an extent that it resisted about 5% to 50% less than it should have (mean resistance around 85% of 1944–45 armour plate). Also British armour of greater than 57mm to 63mm was flawed until about 1944.

The BHN of steel is not directly related to flaws. Some Soviet T–34 BHN 450 armour was relatively flaw free, while other plates of the same thickness in the same tank were quite flawed, as shown by tests conducted by Watertown Arsenal in the USA.

For the technically minded: flaws are things like stringers, laminations, inclusions, and transformation by-products which are in dirty or improperly heat treated steel. Flaws also include crystalline microstructure, as opposed to the ductile microstructure of correctly made, sufficiently alloyed steel.

[Paul Lakowski]

Originally posted by :USERNAME::

READ CLOSELY THE WEBSITE!!!

It claims that the 75mmL24 fired K Gr rot Pz (was APC) and Pzgr. (Kw. K. 38). This is NOT Pzgr 39!! My cutaway drawings show that this "38" round appears to have a large HE cavity in it and the websites data backs this up.

Sorry. I take my german ammunition a bit serious.

Pzgr. (Kw. K. 38)

?

TNT

1.33 kg.

90% PETN

Bd. Z. F. 7.5 cm. Pz. gr.

black

-

Pzgr. 39 FES

APCBC

RDX

83 gm.

90% PETN

Bd. Z. 5103

black w/red marking

-

Pzgr. 39 Kw. K. 40

APCBC

Cyclonite

82 gm.

90% PETN

Bd. Z. 5103

black w/red band/marking

Lewis

Don't play games with me! What are the REAL differences. A small difference in the blasting charge probably won't change any thing the real issue is .... the size and shape of the penetrator as this is what does the penetrating.Blasting charges are for after penetration effect.

Does any one have cut away drawings of the 75L24 Pz rot round?

[:USERNAME:]

Originally posted by Paul Lakowski:

Don't play games with me! What are the REAL differences. A small difference in the blasting charge probably won't change any thing the real issue is .... the size and shape of the penetrator as this is what does the penetrating.Blasting charges are for after penetration effect.

1.33Kg vs 82 or 83 gm? Thats small?

Considering the reduced density of explosive compared to metal, that makes a big difference. In the cross sectional drawing, this is obvious. The charge takes up space well up into the shell.

It really seems to be some sort of concrete buster shell. Really a hardened HE, almost, with a cap on it.

And for those people that think this is anal. You are correct, it is. In that, we want things modeled correctly. If its too much then go play panzer general.

Lewis

PS Even the K. Gr. rot Pz.

APC

TNT

114 gm

Had a 50 percent larger charge

[This message has been edited by :USERNAME: (edited 01-28-2001).]

[Bullethead]

PzI said:

I have been posting the AQ problem with the CH armor for months now & been ignored here

There's probably a reason for that

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

-Bullethead

In wine there is wisdom, in beer there is strength, in water there is bacteria.

[:USERNAME:]

Originally posted by PeterNZer:

I value your posts Rexford, always informative and full of good detail. Pitty Username has to get so excited.

PeterNZ

I pity your spelling PetterZNer.

In the dictionary theres pitter-patter. Like the pitter-patter of my 37mm halftrack knocking out your poor quality M18 armor. Pity you broke cover with those TWO vehicles and decided to parade them in front of my unarmored ambushing flak-track. you threw away the game at that moment. Any fool would have had one break cover while the other overwatched.

Your lack of tactics is only matched by your lack of tact. I guess the desire to parade around is distilled in you now as an honorary limey.

On a serious note, Belton has something to say about US cast armor. He claims it never stopped anything on its way through.

Lewis

[This message has been edited by :USERNAME: (edited 01-28-2001).]

[Guest Germanboy]

Originally posted by M. Bates:

Anal.

Seriously Ksak, surely these guys are furthering our knowledge?

M.Bates, there is no point in arguing with Ksak, he has shown already that he does not care about anyone doing actual research.

Rexford, I too think your posts are very informative and they have obviously contributed a lot to the game alredy. I hope that the thickheadedness of some people won't deter you from posting the info you have got.

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

Andreas

Der Kessel

Home of „Die Sturmgruppe“; Scenario Design Group for Combat Mission.

[rexford]

The British National Physics Lab equation suggests that as projectile diameter increases 152mm plate resists like less and less. And if the hardness of 152mm plate was 220 Brinell, which is possible, the quality modifier would be alot lower than 0.92 against 88L56 and 75L70.

Aren't there any battle reports that suggest penetration ranges for Tiger I and Panther, or 75 and 88 Pak, against Churchill 7 frontal armor? We looked and were not able to find much. This would really be valuable input if anyone has info.

Another issue is when during 1944 did British improve quality control, and how many Churchill 7's had already been cranked out? U.S. instituted improvements during October '43 in quality control and heat treatment, until then firing tests passed alot of deficient stuff.

We live in USA and had ready access to lots of WW II documents at little cost thru National Technical Information System at State Library in Albany New York. British stuff came from Bovington but was mostly North Africa.

We never got to 1944 and 1945 combat from British view.

There is also the issue of added armor in contact. Two machineable quality homogeneous plates of 40mm thickness in contact resist like less than 80mm on perpendicular hits. There is alot of add-on homogeneous on Allied tanks, Sherman Jumbo and several British tanks.

Super Pershing adds plates over basic Pershing, but spaced plates resist with less gusto than plates in contact. CM treatment of spaced and contact armor may need re-examination.

[PzKpfw 1]

Originally posted by Bullethead:

PzI said:

There's probably a reason for that

LOL Bullet, we will see .........

Regards, John Waters

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

"We've got the finest tanks in the world. We just love to see the

German Royal Tiger come up on the field".

Lt.Gen. George S. Patton, Jr. February 1945.

[Jeff Duquette]

David Fletcher's book "Mr. Chruchill’s Tank" has a fair number of reference AAR's for N. Africa indicating the Churchill's ability to stand up to a great deal of punishment from German 37mm and 50mm rounds. I'm digging for AAR's detailing Churchill's in ETO where heavy caliber German weapons are involved.

The following summarizes German reports based on tests conducted on Churchills captured during the Dieppe raid.

From: David Fletcher’s “Mr. Chruchill’s Tank, The British Infantry Tank Mark IV”

The Allied lessons of Dieppe are beyond the scope of

this work but it gave the Germans a chance to evaluate the

Churchill at their leisure. As the prisoners were rounded up,

wounded and dead removed and the fires died down, the

tide crept in to swamp some of the tanks. Those that were

still running were used to drag others from the beach and

they were examined briefly in the Dieppe area.

A copy of the German report came into British hands in

the Middle East and it was sent to London for translation. As

a Colonel from the Military Intelligence branch M.1.10 re-

marked "the comparisons made here are not flattering". The

Germans compared the Churchill not only to their own tanks

but to the Russian machines they were now encountering in

the east. And it did not compare favourably. The vehicle' says

the report 'offers nothing worthy of consideration by technical

personnel, nor has it any new constructive features either in

the metallurgical field, or in the field of weapon technology'.

The 3 inch howitzer was 'bad and old fashioned'; the 2-

pounder left behind both in construction and effectiveness'

while the 6-pounder's performance 'does not approach that

of Russian guns of the same calibre'. Ammunition revealed

no new or noteworthy features and, as for armour it was seen

as very thick but of poor quality and did not compare well

with German or Russian plate.

They also claimed that the

tracks were brittle and of clumsy design which fractured ev-

ery time it received a direct hit. Photographs seem to indicate

that the Churchills abandoned at Dieppe had the heavy, spud-

ded cast track made from a material described as B.T.S. 3.

Discussing performance the Germans noted that the

tracks made so much noise that they believed it would be

impossible for anyone to use the radio while the tank was

moving. No similar complaint is heard from British sources

but the Germans made the point that when the tank halted to

use its radio it provided a good opportunity to knock it out.

Not that this was regarded as a problem. As the report sums

up ' The shape is also not modern. In conclusion it may be

said that the English Churchill tank, in its present form, is

easy to combat'.

[Paul Lakowski]

Originally posted by :USERNAME::

1.33Kg vs 82 or 83 gm? Thats small?

Considering the reduced density of explosive compared to metal, that makes a big difference. In the cross sectional drawing, this is obvious. The charge takes up space well up into the shell.

Actually the reduced density probably won't make that much difference. In the change from BR-350A to BR-350B the filler charge goes from 0.06 Kg to 0.15kg and this only results in a 5mm increase in penetration . However the projectile is 234mm long [bR-350B] compared to 221mm for the BR-350A. This increase in length is the primary reason for increased penetration.

It really seems to be some sort of concrete buster shell. Really a hardened HE, almost, with a cap on it.

And for those people that think this is anal. You are correct, it is. In that, we want things modeled correctly. If its too much then go play panzer general.

Lewis

PS Even the K. Gr. rot Pz.

APC

TNT

114 gm

Had a 50 percent larger charge

Lewis show me a drawing cause thats all that matters right now!

[:USERNAME:]

Originally posted by Paul Lakowski:

Lewis show me a drawing cause thats all that matters right now!

The German Sturmgeshuetze in WWII

pg 31.

Its that hard for you to conceptualize things from numbers?

Lewis