Allied tank armor, quality control

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
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Re: Allied tank armor, quality control

Post by Contender » 24 Apr 2020 21:01

The Panzer IV "F2"-G armed with the 7.5 cm KwK 40 L/43 uses the Tzf 5F optic, the Panzer IV H & J armed with the 7.5cm KwK 40 L/48 uses the Tzf 5 F2. The Tzf 5F2 features higher ranges for the Pzgr 39 round than the earlier sight.
As stated above we know there was an increase in power charge during the war & there is that 1944 document that lists the Muzzle velocity as 770 m/s adding the increased range from the later optic implies the L/48 should have a higher MV compared to the L/43.

I personally believe the KwK 40 L/48 's muzzle-velocity is greater than 750 m/s at least in the 770 m/s range the lower figure is a result of the L/43, the use of Trop rounds & I think some of the data for example from Pawlas's datenblatt took the lowest number for the weapon system or perhaps early data due to several weapons having similar ballistics but different MV for example the soviet 76.2 mm Pak 36 (r),76.2 mm Pak 39(r) (the guy is shorter than the 36), 75mm KwK 40 L/43, Pak 40 & 75mm KwK 40 L/48, you will notice in Pawlas's book the same penetration figures (they are identical) printed for all these weapons & the Stuk 40 as well.

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Re: Allied tank armor, quality control

Post by Peasant » 15 Aug 2020 13:26

Hope this hasnt been posted here yet.

Source: "Mr. Churchill's Tank: The British Infantry Tank Mark IV" by David Fletcher
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Re: Allied tank armor, quality control

Post by Peasant » 22 Apr 2021 08:14

Look what I found. The official US specs for cast armour from 1956 call for minimum BL(A) for a 3,5in. casting of 1350fps, which this one piece failed to reach. It is likely that the ballistic resistance of US armour improved by 1944.

Another thing this confirms is that the recoil cylinders of the gun mount on the 76mm armed Shermans, are protected just by the gun mantlet and can be damaged by any shell that can pass through this thickness of armour. The internal spall shield would probably protect the crew though if the cylinder stops the shell.
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Re: Allied tank armor, quality control

Post by Yoozername » 23 Apr 2021 14:16

Report drawn up on 02.07.1943 by I./Pz.Rgt 5 (subordinate to 21. Pz.Div.) Reporting on the experiences in combat with the American M4 'General Sherman' tank.

Note :
The unofficial but widespread designation used in the document "Pz.IV / L" refers to the version of the Panzer IV with a long barrel (Lang) 7.5-cm-KwK 40 L / 43. In the course of subsequent battles, this same Battalion would capture an M4A1 that would be sent to Germany to be evaluated by the Heereswaffenamt and of which there are multiple photographs.


Origional German

http://www.panzer-elmito.org/enemigo/in ... 943_D.html
Africa, 07.02.1943

I./Panzer-Regiment 5
Abt. Ia / Ic Nr. 11/43 geh.

In relation to :
Pz.Rgt. 5 Ia / Ic Nr. 30/43 geh. from 02.06.43

Subject :
Experiences against the American M4 tank

General :

Between 31.01. and 01.02. west of Faid the Battalion had contact with an American heavy armored battalion consisting mostly of M4 'General Sherman'. 11 tanks and a self-propelled gun (model unknown) were destroyed. So far the M1 'Dreadnought' tank has not appeared. Own losses: 3 Pz IV / L tanks damaged.

Results of the inspection of the burning tanks :

No perforation was found in the upper parts of the hull. 8.8 cm shells fired by anti-aircraft guns and 7.5 cm armor-piercing shells have pierced the turrets. An 8.8 cm grenade ricocheted off the rounded top of the hull and was redirected against the turret and still managed to pierce its armor.

The weakest area of ​​the M4 is its chassis. In an M4, a perfect 5 cm perforation was found in the front area of ​​the chassis (apparently very brittle steel), achieved at a distance of 1400 meters. Large and irregular perforations have been found in several 'General Shermans', probably caused by hollow charge projectiles.

A large number of lateral perforations show that thanks to its weak armor as well as the advantageous angle the M4 is very susceptible on its flanks.

Combat method of the American tank :

From its concentration zone to approximately 4000 meters slow advance. Fire opening from 3000 meters but without any effect on our well sheltered battle tanks. Everything seems to indicate that the American crews did not have much combat experience. The attack conveyed an impression of indecision. Apparently the Americans trusted blindly in the thickness of their armor. When the first enemy tanks began to burn, everything stopped. Apparently the visibility conditions of the commander of the M4 towards its sides are bad. The attacks of our tanks against their flanks were either not recognized or they were discovered when it was too late.

The Americans love to initiate the attack by firing high-explosive shells at ranges of 4000 and 6000 meters. The M4 is also used and successfully in artillery work.


Effects of our weapons on the M4 :

The main weapon to combat the M4 is the Pz.IV / L, effective from 1800 meters. Impacts achieved at distances greater than 1800 meters (except against the frontal area of ​​the hull) still have effects and can lead to disable their weapons or even to the crew abandoning the battle tank. Impacts have even been achieved at distances of up to 2000 meters, especially against its sides, which have caused the vehicle to burn. The effects of 7,

Most of the M4s were destroyed at ranges between 1,200 and 1,600 meters. Also the hollow charge grenades (7.5 cm long and short) have been used with good success, although in these cases the consumption of ammunition is very high since it is difficult to sharpen the aim because the impacts of the projectiles are very difficult to detect. watch. The 5 cm armor-piercing projectiles are only effective at ranges up to 1200 - 1400 meters.


Conclusion :

It must be tried to let the enemy approach and fight it from advantageous and sheltered positions. In the attack, the objective must be to envelop or surpass the enemy's flanks to achieve the effective combat distance of our tanks from 800 to 1600 meters: the poor lateral visibility of the M4 and the inexperience of the Americans play in our favor. In the frontal attack you should only point against the area of ​​the bathtub between the two chains.



Signed: Gruen,
Hauptmann and Battalion Chief

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Re: Allied tank armor, quality control

Post by Peasant » 23 Apr 2021 17:25

Yoozername wrote:
23 Apr 2021 14:16
Very interesting read.

I'm surprised by the resistance of the UFP on these M4 tanks. From the description these were the early ones with 56° sloped cast glacis plate. As it was able to provide adequate protection against the german 7.5cm L/43 gun at 1200-1400m, it's equivalent thickness was at least of 90-100mm.

That perforation of the transmission cover at 1400m was an extremely lucky shot. At that distance the 5cm PzGr.39 fired at 835m/s will have only 509m/s left. The G(d) penetration at this velocity is about 40mm/30° or 49mm of vertical RHA.

From the description they shelled the german position with HE shells from long range before attacking. I wonder whether at this point the US 75mm guns had smoke round available, they would've been of great help for assaulting enemy position across long stretches of open ground like in this case.

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Re: Allied tank armor, quality control

Post by Richard Anderson » 23 Apr 2021 18:29

Peasant wrote:
23 Apr 2021 17:25
That perforation of the transmission cover at 1400m was an extremely lucky shot. At that distance the 5cm PzGr.39 fired at 835m/s will have only 509m/s left. The G(d) penetration at this velocity is about 40mm/30° or 49mm of vertical RHA.
That is odd. I wonder what the original German said? I suspect the translator may have confused Laufwerk for "chassis", insofar as chassis in German is chassis. 8-) The PSC M4A1 with 1st AD in Tunisia had the improved 1-piece differential, and I have found little to indicate there were problems with brittle casting of those. So did the PSC M4A2 issued to 1st AD. I suspect they are referring to the lower hull side and suspension rather than the transmission cover.

It is also interesting that they speculate the commander had limited visibility to the sides. Sole visibility from the turret was the gunners periscope and the commanders periscope, easily leading to tunnel vision to the front by inexperienced crew.
From the description they shelled the german position with HE shells from long range before attacking. I wonder whether at this point the US 75mm guns had smoke round available, they would've been of great help for assaulting enemy position across long stretches of open ground like in this case.
Yes, 75mm CS was available, but they were probably using standard 75mm M48 HE and 75mm M72 AP, since I don't think the 75mm M61 AP arrived in Tunisia until later. The real problem was that tactically, the American tankers attack was supposed to be in waves maneuvering forward with elements firing in support on the rear flanks, typically in a company it was an advance by one platoon, supported by a second platoon firing, and the third in reserve to continue the advance if the advancing platoon was halted by fire or to envelop the enemy position. The idea was to get the tank wave into the enemy position in direct assault, rather than a deliberate advance by bounds from covered firing position to the next. To call American armor tactics in this period primitive is to say the least.
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Re: Allied tank armor, quality control

Post by Yoozername » 24 Apr 2021 03:25

I think this Sherman (note the Germans did use 'General Sherman' in the report?) probably represents the targets in the account (if not the actual targets?). The Germans are speaking of targeting the cast 'tranny' cover on specific spots. I have read of other reports of this. Basically, it can be penetrated and immobilize the AFV.
shermin.jpg
shermlh.jpg
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Re: Allied tank armor, quality control

Post by critical mass » 24 Apr 2021 09:57

2.) Untersuchungen der abgebrannten Feinpanzer ergab folgende Feststellung:
Im Panzerkasten-Oberteil waren keine Durchschüsse. 8.8cm Flak and 7.5cm Pz.-Granaten hatten die Türme durchschlagen. Eine 8.8 cm Granate war auf dem abgerundeten Pz.-kasten-Oberteil abgeprallt und gegen den Turm getroffen, wo noch ein Durchschlag erzielt wurde.
Die empfindlichste Stelle am M4 ist die Panzerwanne. An einem M4 wurde in der Bugwanne (anscheinend auch spröder Stahl) ein glatter 5 cm Durchschuss festgestellt, erzielt auf 1400m. Einige General-Sherman hatten grosse, unregelmäßige Einschussöffnungen, die wahrscheinlich durch die Holhlraumgranate hervorgerufen worden waren.
thus,
no-penetrations through M4 glacis. Perforations were obtained by 8.8cm AAA and 7.5cm Pz.Gr. [my note: at long range] on the turret. A 8.8cm projectile ricochetted off from the rounded glacis and still perforated the turret.
The lower hull casting was considered most vulnerable to perforation. One knocked out M4 exhibited a clean 5 cm perforation through the (lower) front casting, which was achieved at 1400m. Brittle fractue was suspected in this case. Large, irregular holes in some M4 were attributed to probably have been caused by HEAT-projectiles.

my note: HEAT impacts should not leave large, irregular holes, but small ones (generally sub calibre). This might indicate presence of temper brittleness if the holes came from regular AP proectiles, instead. The performance of the sloped glacis to ricochett off incoming large calibre AP was admirable, in fact, better than the T34´s glacis from similar thread. This also indicates a good ductility of the casting, somewhat in variance to the lower hull casting.

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Re: Allied tank armor, quality control

Post by Richard Anderson » 24 Apr 2021 16:55

critical mass wrote:
24 Apr 2021 09:57
thus,
Thanks.
no-penetrations through M4 glacis. Perforations were obtained by 8.8cm AAA and 7.5cm Pz.Gr. [my note: at long range] on the turret. A 8.8cm projectile ricochetted off from the rounded glacis and still perforated the turret.
The lower hull casting was considered most vulnerable to perforation. One knocked out M4 exhibited a clean 5 cm perforation through the (lower) front casting, which was achieved at 1400m. Brittle fractue was suspected in this case. Large, irregular holes in some M4 were attributed to probably have been caused by HEAT-projectiles.
Okay, so they were likely referring to the 50.8 mm-thick transmission cover. Quite lucky to achieve a clean penetration at that range. If it was "clean" wouldn't that indicate it was much more malleable and much less resistant, since a clean penetration doesn't seem to infer a brittle fracture?
my note: HEAT impacts should not leave large, irregular holes, but small ones (generally sub calibre). This might indicate presence of temper brittleness if the holes came from regular AP proectiles, instead. The performance of the sloped glacis to ricochett off incoming large calibre AP was admirable, in fact, better than the T34´s glacis from similar thread. This also indicates a good ductility of the casting, somewhat in variance to the lower hull casting.
Yes, the assumption that HEAT left large irregular holes is odd. Probably due to the officers lack of experience/knowledge of its effects?

In any case, the quality of the lower casting could have been different, because the manufacturers were different. In Yoozername's second photo it appears the upper casting was from General Steel out of Eddystone, Pennsylvania. The lower casting was from American Steel's plant in East Chicago, Indiana. It is quite possible that the armor in the tanks referred to in the German report were sourced from different steelmakers as well. IIRC, S.A. Herres and A.M. Turkalo, Repair Welded Cast Armor, Metallurgical Examination of Samples Representing Ninety-six Two Inch Thick Ballistic Test Plates, Memorandum Report No. WAL 647/8, (Watertown, N.Y.: Watertown Arsenal Laboratory, 7 February 1945) notes some of the wide quality variances between manufacturers versus War Department specifications. Part of the problem was the lack of expertise and equipment for testing armor quality at BRL and Watertown until quite late in the war.
"Is all this pretentious pseudo intellectual citing of sources REALLY necessary? It gets in the way of a good, spirited debate, destroys the cadence." POD, 6 October 2018

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Re: Allied tank armor, quality control

Post by Yoozername » 24 Apr 2021 18:41

critical mass wrote:
24 Apr 2021 09:57


my note: HEAT impacts should not leave large, irregular holes, but small ones (generally sub calibre). This might indicate presence of temper brittleness if the holes came from regular AP proectiles, instead. The performance of the sloped glacis to ricochett off incoming large calibre AP was admirable, in fact, better than the T34´s glacis from similar thread. This also indicates a good ductility of the casting, somewhat in variance to the lower hull casting.
In some cases, like bazooka rounds, the angle of impact can deform the cone, resulting in odd shaped penetrations. In any case, I would be surprised that they would fire HL ammunition at those ranges. Certainly not at moving targets. Miles published the shooting tables for Pak 40, which would have similar velocity to the KWK L43 for HL, and it would almost be depending on luck at that extreme range.

Can you translate paragraph 4 from the original document?

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Re: Allied tank armor, quality control

Post by Yoozername » 24 Apr 2021 19:06

Clean hole through the casting

Image

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Re: Allied tank armor, quality control

Post by Yoozername » 24 Apr 2021 19:24

An interesting report from Jan 44. I would assume the target is a M4A3?
Battalion Command Post, 20.01.1944

Pz.Jäg.Abt. 235

Commander

Addressed to : 198. Infanterie-Division

Shooting tests with one of the enemy tanks destroyed on 19.1.1944 of the 'General Sherman' model have shown that light anti-tank guns can still be used successfully for anti-tank fighting. At a distance of 200 m and both with Pz.Gr.40 and Pz.Gr.39, the 3.7 cm anti-tank gun manages to pierce the sides without any problem, while these projectiles have rebounded against the turret and the frontal zone .

Tests with the 4.5 cm anti-tank gun (Russian) gave the same good results.

The invulnerability of the frontal zone and of the turret against both guns, as well as the promising possibility of success against all sides of the vehicle, make it necessary to operate with a minimum of 2 guns of these calibers and in such a way that both protect each other.

The use of 'Faustpatrone' against the front (distance of 30 m) resulted in a perfect perforation and the immediate fire of the battle tank. The 'Faustpatrone' therefore continues to be the best weapon for proximity anti-tank combat ( Panzernahbekämpfungsmittel ) and its use should be practiced whenever possible.

While not all units can be equipped with a sufficient number of 'Faustpatrone', the use of the rest of the proximity anti-tank weapons must be continuously trained.


Signed: Fasel

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Re: Allied tank armor, quality control

Post by critical mass » 24 Apr 2021 20:24

Richard Anderson wrote:
24 Apr 2021 16:55

Okay, so they were likely referring to the 50.8 mm-thick transmission cover. Quite lucky to achieve a clean penetration at that range. If it was "clean" wouldn't that indicate it was much more malleable and much less resistant, since a clean penetration doesn't seem to infer a brittle fracture?

(...)
In any case, the quality of the lower casting could have been different, because the manufacturers were different. In Yoozername's second photo it appears the upper casting was from General Steel out of Eddystone, Pennsylvania. The lower casting was from American Steel's plant in East Chicago, Indiana. It is quite possible that the armor in the tanks referred to in the German report were sourced from different steelmakers as well. IIRC, S.A. Herres and A.M. Turkalo, Repair Welded Cast Armor, Metallurgical Examination of Samples Representing Ninety-six Two Inch Thick Ballistic Test Plates, Memorandum Report No. WAL 647/8, (Watertown, N.Y.: Watertown Arsenal Laboratory, 7 February 1945) notes some of the wide quality variances between manufacturers versus War Department specifications. Part of the problem was the lack of expertise and equipment for testing armor quality at BRL and Watertown until quite late in the war.
Thank You. A good hint and much appreciated. I will locate the item for my reference. Quality variances between manufacturers should be realistically reckoned with. After all, these very large armor castings represented a new technology and variances in the heat as well as heat treatment challanges were enoumous at first.
In regard to "clean penetration / glatter Durchschuss", when judging the context, I have the impression that clean penetration is meantioned in order to emphasize a perforation event (whole projectile through the plate) in order to differentiate it from break up, holing or burst in holing events. It´s not used in this context (dealing with fire effect) to describe the failure mode of the armor itselfe. Unfortunately, and to add our confusion, prooving ground reports do indeed use the same terms to describe plate behavior when the context is relating to assessment of armor plate). The failure mode of this lower hull casting was singled out as apparently brittle with the terms immediatly following: "anscheinend auch spröder Stahl". Notice, its not a qualified assessment. Its a secondary interpretation by crews and subject to potential error.

Tentatively, I´d interprete this is an example of a rare or somehwat unexpected event, which explains why they needed to qualify the cal., distance and perforation event and added the apparent brittleness of the steel.
Can you translate paragraph 4 from the original document?
sure.
Eigene Waffenwirkung auf den M4
Der Hauptträger des Kampfes gegen den M4 ist der Pz.-Kpfw, IV/L, wirksam ab 1800m. Bei Treffern [ü]ber 1800m (ausgenommen Bugwanne) immerhin eine Stoss- und Schockwirkung, dass mit Unbrauchbarwerden der Waffen oder mit Ausbooten der Besatzung gerechnet werden kann. Es wurden auch Treffer auf 2000m, insbesondere seitlich erzielt, die den M4 in Brand setzten. Abh[ä]ngig ist die Wirkung auch der 7,5 cm Pz-Granate lang bei diesen Entfernungen davon, ob sie zuf[ä]llig auf einer gerundeten oder schr[ä]gen Fl[ä]che trifft und abprallt, oder an einer senkrechten Stelle (Bugwanne zwischen den ketten, Seitenwanne, Turmstirnseite) den Durchschuss erzielt. Die Masse der M4 wurde auf 1200 bis 1600 m abgeschossen. Dabei hatten auch die Hohlraumgranaten (7,5 cm kurz und lang) sehr gute Wirkung; jedoch ist ein erheblicher Munitionsaufwand daf[ü]r n[ö]tig, da ein Einschiessen erforderlich ist und die Aufschl[ä]ge schwer zu beobachten sind. Die 5 cm Panzergranate verspricht nur bis 1200/1400 m Erfolg.
own fire effect upon M4
The main carrier of the fight against the M4 is the mark IV/L [my note: by british period nomenclature this would be labelled as mark 4 special, with the long 7.5cm gun]. It is effective to 1800m. Except for hits on the lower casting, hits beyond 1800m still exhibit shock effects, from which disabling of weapons or the abandonment of its crew maybe reckoned with. Hits from 2000m, particularely upon the vehicles side armor, set the tank alight. The fire effect of the 7.5cm Pz.Gr. on such distances depends largely upon whether it randomly hits on a rounded or sloped plate and consequently, ricochetts off or,alternatively, on a more perpendicular plate with complete perforation following (lower front casting between the tracks, side hull plates, turret front).The majority of the M4 were knocked out at 1200-1600m range. At this range, HEAT projectiles from short or long 7.5cm guns, too, had very good effect, but required high ammunition consumption because ranging shots were necessary and the fall of shot as well as hits were difficult to observe. The 5 cm Pz.Gr. is only effective to 1200/1400m.


Interestingly, in a later report from combat in january 1944, StuG´s considered only ranges up to 800m effective:
[link]http://www.panzer-elmito.org/enemigo/in ... 944_D.html[/link]

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Re: Allied tank armor, quality control

Post by Peasant » 24 Apr 2021 22:34

The german values for the performance of 3.7cm AT gun are somewhat pessimistic as they were obtained against 110-125kg/mm^2 plate (about 323 - 347 BHN) while the US specifications for vehicle plate of 38mm is between 280-310 BHN. I believe this difference itself should not influence significantly it's resistance against intact projectile of 37mm caliber (although the softer plate might perform better at 0° obliquity) but it would definitely cause less damage to the attacking projectile, which was what caused the performance curve flattening out in the german data.
I estimate an intact 3.7cm PzGr. should be able to defeat 38mm/30° US vehicle plate at up to 300m distance and up to 500m with a perfectly perpendicular hit.

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Re: Allied tank armor, quality control

Post by Yoozername » 25 Apr 2021 01:45

Thanks for the translation, Elmito seemed to lose part of it.

Another issue with cast armor is its thickness variation. It has to be designed into a vehicle such that variations must fit at certain points of the structure. I would venture that many cast parts are further machined or heat worked etc. So, they may seem a great shortcut, but there could be many issues including rejects getting thrown back in the smelter. I wonder if any nation was doing vacuum casting. It basically means the molten metal is pumped up into a mold, and there is a vacuum at the top to draw out any trapped gases. I doubt they did lost foam, pretty sure that is a modern method.

But as far as a specification, like RHA for the Germans being -0/+5, it would not be achievable. A good example is the Germans trying to put any weapon to use in the last months of the war. For whatever reason, the JagdPanther gun was in surplus. It was desired for it to be in a static ground mount (on a turn table) and also keep the rounded cast mantlet. But a big issue came up regarding the balance on the weapon. It seems that each mantlet had a weight difference that was substantial. The contractor wrote a report about it.

The US moved away from the largest castings on the M4. Some crews preferred the rounded hulls. I wonder if the Soviets had an opinion on each type of hull? Or did they just get RHA shermans?

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