Thick British AFV Armour

[Jeff Duquette]

A couple images From: “The TigerFibel”. The Fibel evaluation of the MkIV: “Heavy Armor and difficult to combat. Slow tactical effect and cumbersome. Not suitable for operational use.”

[rexford]

According to Duquette's post, German analysis of Churchill at Dieppe clearly indicates poor quality armor with 88mm thicknesses. What about 152mm thickness at a time that British industry was struggling to produce?

We really need actual penetration range figures on true Churchill VII resistance.

95% quality is probably optimistic for Churchill VII, since it appears to be consistent with best quality penetration test plate, and may not represent mass produced tank armor.

[rexford]

Tiger Fibel penetration ranges appear to be office calculations for 30° hits from target facing, without armor quality or cast armor considerations.

Turret front on Mark IV Churchill penetrated at 2000m and 30°, which doesn't seem like a difficult target.

Almost 1000m penetration range against driver plate on 30° hits, without armor quality factor.

Does CM penalize armor for cast manufacture, which results in different and less resistant structure than rolled armor.

[Guest Germanboy]

Originally posted by rexford:

According to Duquette's post, German analysis of Churchill at Dieppe clearly indicates poor quality armor with 88mm thicknesses. What about 152mm thickness at a time that British industry was struggling to produce?

sorry - don't understand what you mean here. Just a bit of info - the Churchill in Dieppe was a vastly different tank from those eventually landed in Normandy, AFAIK.

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Andreas

Der Kessel

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

[rexford]

Just a note that Dieppe Churchill armor quality was poor, and this was early in war. Shows that British armor was not always good quality.

If 88mm armor is poor, what happens with 152mm armor, since thick armor introduces additional burdens and problems compared to 88mm.

The above logic doesn't prove anything, but identifies early armor problems which other sources say wasn't resolved till sometime in 1944.

[rexford]

British NPL equation predicts that 152mm of British armor at 220 Brinell Hardness will resist like 137mm of good quality rolled armor (250 Brinell Hardness) against 75mm hits, and 132mm against 88 hits.

This is alot less than 95% factor used in CM.

[rexford]

If 88mm Churchill armor is sub-par, the question might be asked if 152mm would be better given alloy shortages and mass production demands later in war.

The NPL equation predicts that 152mm of British armor at 220 Brinell Hardness would resist 75mm hits like 137mm of good rolled armor, and would resist 88mm hits like 132mm. This is alot less than CM predicts (95% x 152mm = `144mm of good rolled armor).

[rexford]

If 88mm armor on Churchill is poor early in war, before mass production dilutes alloys, one might suspect that 152mm later in war would be as bad, if not worse. Interesting speculation.

NPL equation predicts that 152mm at 220 Brinell Hardness would resist 75mm hits like 137mm of good rolled armor, and resist 88 hits like 132mm: alot less than CM predicts.

[Paul Lakowski]

Originally posted by :USERNAME::

The German Sturmgeshuetze in WWII

pg 31.

Its that hard for you to conceptualize things from numbers?

Lewis

No thats not what I'm after, I have an erosion based penetration formula thats needs info like projectile lenght and diameter not things like basting charge size.

Are there any other sectioned diagrams for 75L48 , 75L 70 and 88L71 ammo with some measurement figure?

[Simon Fox]

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'.

So that must be a different Churchill to that encountered by the Germans in North Africa, right? A German commander was heard to declare "I am being attacked by a British supertank" after a Churchill shrugged off a point blank hit from an 88 and proceeded to wreak havoc on his force.

Bulletheads point is a good one, it is very perplexing given the quality of British naval armour. The question really is when did British armour production get its' act together.

Also the point about applique armour for Churchills is a good one but it cuts both ways. Many so called Churchill VIIIs are really uparmoured early versions. So what is better 152mm of 'dud' armour or multiple plates of 'good' armour?

Which German projectiles 'overmatch' 152mm armour?

How does 'face hardened' armour respond to overmatching projectiles?

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"As has been said, we only listen to bootlickers, and Simon is one of the best out there!"

[Guest Germanboy]

Originally posted by Simon Fox:

So that must be a different Churchill to that encountered by the Germans in North Africa, right? A German commander was heard to declare "I am being attacked by a British supertank" after a Churchill shrugged off a point blank hit from an 88 and proceeded to wreak havoc on his force.

Bulletheads point is a good one, it is very perplexing given the quality of British naval armour. The question really is when did British armour production get its' act together.

Also the point about applique armour for Churchills is a good one but it cuts both ways. Many so called Churchill VIIIs are really uparmoured early versions. So what is better 152mm of 'dud' armour or multiple plates of 'good' armour?

Which German projectiles 'overmatch' 152mm armour?

How does 'face hardened' armour respond to overmatching projectiles?

Simon, can you please email me about a question I have regarding Churchills?

Rexford - there is a possibility that the British factories simply got better over time at producing tank armour, due to experience. Two years are a long time to learn. Just surmising, but since that is what we are down to here at the moment.

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Andreas

Der Kessel

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

[:USERNAME:]

[Kurtz]

It seems like there often is "internal armor flaking" when a Churchill is hit with something that doesn't penetrate the armor but I have not seen any crew casualties due to this.

Has anyone else noticed this?

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SS-Weihnachtsgrenadiere

[Jeff Duquette]

Kurtz Said:It seems like there often is "internal armor flaking" when a Churchill is hit with something that doesn't penetrate the armor but I have not seen any crew casualties due to this.

Fletcher discusses this problem in "Mr. Churchill's Tank". Test firing conducted on the welded turret for the MkIV indicated interior flaking\spalling. There were also other problems associated with the cast type turrets.

Fletcher indicates that many of the Churchills seeing action in ETO during 44-45 were actually the MkIV type. Many of these machines would have been constructed during 42-43.

I reckon with a world at war, in which steel production for all nations was being pushed to the limit,…ships, aircraft, tanks etc. I wonder if it reasonable to think that quality control was as strict as it could have been. Reading through the development of the Churchill there was certainly a real since of urgency involved. A lot of corners were cut in both the design process and manufacturing process. There was actually discussion at one point detailing the exclusion of the tanks turret basket. The TC and Gunner seats were to consist of slings hung from the turret roof, and the loader would be expected to shuffle about the turret floor during traversing.

[Kurtz]

Nevermind, I just did a few tests and sometimes there are crew casualties from flaking. I just hadn't encountered it before.

I was not questioning the flaking, rather the (percieved) lack of effect on the personnel inside the tank.

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SS-Weihnachtsgrenadiere

[rexford]

Two plates in contact resist with less resistance than a single plate of same total thickness.

British NPL suggests that when 152mm British is hit by 75mm rounds (undermatching), the armor does not resist like a scaled up 64mm plate but loses resistance. This may be due to difficulties involved in hardening thicker armor.

We ran the NPL equation for 152mm armor hit by 50mm rounds, and in that case 6" armor was equivalent to a scaled up 64mm plate (same quality factor). But 75mm hits on 6" British armor take advantage of whatever hardening deficiencies existed even though the armor is very thick relative to projectile diameter.

And the NPL results are probably against unflawed armor, so flaws might further reduce the resistance.

If Churchill had 88mm base armor of uneven quality plus added 64mm (decent hardening, possible flaws), the result might be equal to a 152mm plate due to resistance loses when plates are in contact.

Equations generated by Nathan Okun predict that 64mm in contact with 88mm resists like a single 133mm plate. If the 88mm plate is bad, the resulting resistance is less.

Robert Livingston has discussed German ammo quality control quite a bit, very few rounds were actually inspected and noses were welded onto the projectile body. In quite a few cases, German ammo was seen bouncing off targets that should have been penetrated.

Germans also admitted that rounds could have cracks.

A bad ammo lot, or soft rounds, could explain alot. North African Churchill has 88mm driver plate and 88mm cast turret front, 88mm L56 APCBC from Flak penetrates about 140mm at 500 yards and 122mm at 1000 yards, based on Mark Diehl's data (which may be American estimates from firing tests and DeMarre equation use).

Does 88mm Churchill armor with great ductility, no flaws and excellent hardening wave off hits from 88L56 inside 1000 yards on the basis of quality alone? Probably not.

Battle reports also suggest that 88mm Flak ammo used early in the war may have been softer than the 61 Rockwell C average hardness of rounds captured in Europe. Didn't 88 hits on KV tanks seem to bounce alot during 1941? Some of these soft rounds may have been used in the late stages of North Africa out of necessity. Soft ammo is also prone to shatter gap failure.

[rexford]

With regard to British factories getting better at tank armor, NPL equation appears to be based on late WW II armor and projectiles, and thick armor loses resistance when the NPL equation is used to predict penetration.

And the NPL equation predicts that British high hardness armor falls apart when overmatched at an angle, where similar German and Soviet plate hit under the same circumstances loses resistance but still puts up a decent fight.

We have looked at this question for a long time and believe, but aren't totally sure, that thick armor on British tanks did not harden properly in many cases and lost resistance. The NPL equation is consistent with thick armor that loses resistance compared to 2.5" plate.

Throw flaws into the mix and things get worse. This is why it is so important to examine actual penetration cases. The 88 bouncing off 88mm Churchill armor at point blank is a valid situation, the round penetrates about 160mm at point blank. Why would it bounce?

Cracked projectile, soft ammo and shatter gap, any number of other factors.

What we need is penetration ranges where projectile penetration can be compared to armor thickness and a rough quality factor can be determined. If 152mm Churchill frontal armor is penetrated by 75L46 at range and angle where penetration is 129mm at 0°, quality multiplier can be determined. This would answer question as to whether 6" armor is deficient.

If other penetration ranges are consistent then we can say that a trend appears to exist, and quality might be estimated a little better.

[rexford]

Closely examined the Churchill drawings in AFV Profile 1, and CM may have messed up Churchill armor.

Nose is 88 @ 20°, CM has 88 @ 0°.

Although driver plate is normally assumed to be vertical, AFV Profile drawing shows driver and MG plates at 20° from vertical. This is an important issue that should be resolved, since it may underestimate resistance by more than 10%.

In addition, there is an added 72mm plate that protects around the MG, if this is on top of 88mm front plate the total protection would be 160mm prior to reductions for plates in contact and edge effects.

Tiger Fibel showed an area on Churchill front hull that could not be penetrated by Tiger 88 at any range with 30° shot, and this is same area where AFV Profile shows added 72mm armor.

So, 88 Flak bouncer at point blank may have hit 72mm on top of 88mm, which would surely stress the round and may bring out any inherent defects.

It is always good to take another close look at tank armor, if only to check CM for little oversights.

[Jeff Duquette]

Rexford:

I know your looking for tales of the MkVII...sorry dont have any yet. Here is some additional poop on the MkIV. Following North Africa a general Assessment report of the MkIV’s performance was apparently prepared. Fletcher provides the following summary:

From: Fletcher's "Mr Churchills Tank" (again)

Finally there were some interesting comments on armour. Protection was required for the turret ring, something which British tanks were notorious for, but the most interesting thing is that the fabricated turret (the welded version of the Mark III) was regarded as tougher than the cast type. Most of the

hatches were in need of a redesign to prevent small arms rounds from being deflected through the hinges and there were problems with the side doors. These were tapered where they fitted into the hull but the brigade discovered that when a door was struck it was pushed in and wedged itself shut so that the crew could not open it to escape. They suggested an internal rim, such as they had noted on German tanks, which should prevent this.

In September 1943 the School of Tank Technology produced a summary based on a survey of battle damage. A total of 41 damaged tanks were considered, of which 20 were victims of mine damage. Basing their study on strikes from projectiles the STT report recorded 81 hits in all, effective

and ineffective. More than 25 per cent of these came from 88mm weapons with 75mm the next most common. Of the 21 tanks not mined, 10 were definitely taken out by 88mm shots but whether from tanks or anti-tank weapons was obviously impossible to say. Part of the survey, which the report admitted was dubious accuracy, claimed that of 20 strikes attributed to the 88mm, only 13 were effective while the 75mm scored 8 effectives from 16 strikes. They regarded this as encouraging, pointing outthat it proved the Churchill's armour was not yet outclassed by the latest projectiles. They calculated that an extra inch of armour would make a great deal of difference, but that would depend upon where it was placed. The 25'h Tank Brigades also records the loss of one tank, T68384 of 515' RTR, which was attacked by a dive bomber. the engine cover and shattered it into three or four pieces before smashing in part of the engine. This in turn started a petrol fire which burned the tank out. It would seem difficult enough for a dive bomber to get one accurate hit upon a tank. Two would have to be quite remarkable.

Looking next at where the projectiles hit the report revealed that it was shared equally between the front, sides and all other areas. The area that concerned them most was the side. They estimated (why they could not be sure is unclear) that the sides of a Churchill were about .75 inch (19mm)

thinner than the front and they believed that the addition of an extra 18mm of armour all round could have halved the casualties from shell fire. However the ratio of effective hits on the sides of tanks was far greater than those on the front and this gave rise to further speculation. There is no mention of the fact that the side presents a much larger target but the report concludes that, since the sides were vulnerable, it would make little difference if they were a bit thinner. Weight saved here could then be applied as extra frontal armour. These were only tentative conclusions based on those tanks that been knocked out. The report recognised that other tanks must have been hit without being knocked out and without details of them the sample was not truly balanced. Whether it would affect future designs remained to be seen.

[Simon Fox]

There is absolutely no doubt that the Churchill underwent massive revision following it's woeful debut at Dieppe.

As pointed out by Andreas we are entering an area of somewhat shakey foundations when we start to make suppositions about late Churchills based on early Churchills.

I think it would be fair to say that the Churchill didn't find a lot of favour in it's tank role although I understand it was considered to be a mobile vehicle (as distinct from fast ).

It was in it's role as the basis for a number of 'funnies' that it really shone. The Brits really loved the Crocodile. The workshops of the 79th armoured division converted well over a hundred Churchills to Crocodiles well after D-Day. The AVRE and it's 'dustbins' were quite useful too, good for bocage and roadblocks, but alas not in CM.

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"As has been said, we only listen to bootlickers, and Simon is one of the best out there!"

[Jeff Duquette]

Another from Fletcher. 4 frontal penetrations by 75mmL70 during a late war engagement with a Churchill @ 500yrds.

Sixth Guards Tank Brigade arrived in Holland at the end of September. They were soon in action, with the Grenadiers and Coldstreams attacking south of Nijmegen while the Scots Guards acted as a back stop. They had gained a healthy respect for the German 88mm in Normandy but now its seems they were coming up against Panthers more frequently, and they soon discovered that its 75mm gun was just as lethal. In a firefight near Overloon a Churchill of No 2 Squadron, Coldstream Guards encountered a Panther just 500 yards away, but was obliged to move out from cover in order to get a shot at it. Four rounds of 6-pounder APDS followed in rapid succession, each striking the German tank on its front plate and each bouncing off without doing any damage at all. The Panther responded to this provocation with four rounds of 75mm AP, all of which penetrated the British tank but, miraculously, did not harm the crew. It is also worth noting that when the survivors if this squadron pulled back from what had been a very uncomfortable position after dark they employed smoke to disguise the exhaust fumes that might tell the enemy that they were on the move.

[This message has been edited by Jeff Duquette (edited 01-30-2001).]

[Guest Germanboy]

Originally posted by Jeff Duquette:

Another from Fletcher. 4 frontal penetrations by 75mmL70 during a late war engagement with a Churchill @ 500yrds.

Almost certainly Churchill Mk IV.

Armour data from this site:

http://www.shadowsfolly.com/WWII/Britain/Churchill.htm

Hull Front, Upper

Mk I-VI: 102

IV: 101@4°

Mk VI-VIII: 139-152

Hull Front, Lower

IV: 89@25°

Hull Sides, Upper

III: 76

IV: 76@0°

VII: 95

Hull Sides, Lower

Hull Rear

III, VII: 50

IV: 64@0°

Hull Top

III, VII: 19

IV: 19@90°

Hull Bottom

Mk I-VI: 16

IV: 19@90°

Mk VI-VIII: 25

Turret Front

III: 86

IV: 89@0°

VII: 152

Turret Sides

III: 76

IV: 89@0°

VII: 95

Turret Rear

III: 76

IV: 89@0°

VII: 95

Turret Top

III: 19

VII: 20

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Andreas

Der Kessel

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

[Jeff Duquette]

Of course its a MkIV. Thats the point. A large percentage of the Churchills going into ETO 44-45 were MkIV's (see my post above)...or at least that's the impression I'm getting from Fletchers book. A fair number of MkIII's & MkIV are indicated on casualty tables for this time period.

Chamberlain ("British and American Tanks of WWII") seems to imply that the MkVI & MkVII were only armed with the 75mm.

[Guest Germanboy]

Originally posted by Jeff Duquette:

Of course its a MkIV. Thats the point. A large percentage of the Churchills going into ETO 44-45 were MkIV's (see my post above)...or at least that's the impression I'm getting from Fletchers book. A fair number of MkIII's & MkIV are indicated on casualty tables for this time period.

Chamberlain ("British and American Tanks of WWII") seems to imply that the MkVI & MkVII were only armed with the 75mm.

About 60% in June 44 according to this website http://www.geocities.com/MotorCity/8418/21agt-1.htm which I use a lot. The VI was only armed with a 75mm. A lot of IV were also converted to 75mm if I understand that correctly. Apparently that first happened in North Africa where 120 Mk IIIs were field converted to 75mm taken from Sherman wrecks. Just stuff I found on the web the last few days really. Interesting that the 8th Army undertook those field conversions, if the 6pdr was supposedly better than the 75mm on AT performance. Anyone know the reasoning behind that?

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Andreas

Der Kessel

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

[Jeff Duquette]

German Said: Interesting that the 8th Army undertook those field conversions, if the 6pdr was supposedly better than the 75mm on AT performance. Anyone know the reasoning behind that?

I'm at work at the moment, but Fletcher (again with Fletcher…sorry it's the most detailed Churchill reference I have at the moment) does have an extensive write-up on the whole 6-pdr, 75mm conversion issue. Rather controversial. Some British Army field ordnance officer, after looking at numerous knocked out Churchills and Shermans, figured out that a Sherman 75mm could be stuffed into a Churchill turret. I can't recall the exact gist at the moment; I thought it had something to do with the superior HE quality of the 75mm. I will post the stuff from Fletcher late this evening, unless someone can verify this before me.

Of additional interest and related to the armour thickness stats you posted above; The Cast turret of the MkIV actually had a the phenomenal turret top thickness of 1.35 inches. Presumably some limitation on thicknesses associated with casting? It's been a while since high school metal shop so all the casting knowledge I have has long since disappeared.

Anyway I think CM models the welded turret top at 17mm not the 19mm you have found. 19mm also agrees with construction drawings provided in Fletcher for the MkIV.

How about a good reference for the Comet? Any suggestions?