"Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

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ThatZenoGuy
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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by ThatZenoGuy » 23 Feb 2021 02:39

So official documents display that no defective plates went by intentionally?

Also please excuse me, as I am not very good at metallurgy myself. In a nutshell you're saying that German armor was designed to resist their own (high quality) projectiles, for maximum protection against them. But this made the plates possibly less resistant to other types of projectiles and if a projectile overmatched this protection, could result in drastic shattering of the plates?

To be honest it's always seemed amusing how people make fun of the Panther shattering from 122 and 152mm projectiles, when any other tank would be incapable of resisting them either. Or the various ballistic test tanks which get hit upwards of 20 or so times which shatter, when in combat such a number of hits would probably end up in a bailing out crew anyways.

critical mass
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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by critical mass » 23 Feb 2021 15:24

The "Sollkurve", which is the principal testing specifications does not show drastic differences in ballistic qualities, such as one would expect when something in order of "50%" is claimed. Yes, late war E plates generally tend to be somewhat less resistent at normal impact (less hardness range) but more resistent at highly sloped impact, which probably is exactly what they wanted as the vertical armor of early ww2 Panzers passed to sloped and angular surfaces late in ww2, which are primarely attacked by oblique impact. It´s a good feature in terms of ballistic resistence.

Of course everybody laid down specifications against the own projectiles, because this item is used to proof armor before it is admitted. The Germans in ww2 did not produce special test shot but used regular service AP for trials. Earlier armor was harder, also face hardened at times, because A) at this time thinner plate was made and thinner plates can be treated to higher hardness without loss in toughness, B) thick armor was layouted without much sloping, presenting farily low angles of attack, and C) earlier german service AP was much less capable to stay intact in a severe ballistic attack (high velocity impact with moderate or high obliquity) than the Pzgr.39, introduced 1942 in service.

German armor was additionally affected by the AP-projectile technology of its adversaries. Fortunately, the allies employed very different paths of how to make AP, causing different forms of attack and failure modes. In metallurgy, You can´t have it all, so one form of resistence against a failure often makes the plate vulnerable to other forms of attack. This forced a compromise in hardness range to negotiate between conflicting requirements.

The SU used low quality shell steel with low hardness with either blunt nosed or pointed projectiles without AP-cap (just windscreen fitted to the blunt variants) with a rather large HE filler. These could generally not stay intact when attacking cal/D plate at normal to moderate obliquity and thus always attacked the shear strength of the plate, even when engaging from normal. On the other hand, this form of attack wouldn´t nearly suffer as much from change of shape effects as plastic deformation failures. Against such a shell, thick, vertical Face Hardened armor (surface induction hardened, not cementated naval FH) would be a premium, because it would facilitate break up and easily shatter the projectile with its large filler. This is why the Soviet Union shifted to high hardness armor on it´s own just before ww2, it was godlike versus it´s own (low quality) shells.
However, by mid ww2 the british employed different AP-capped projectiles, generally without filler and also with very high nose hardness. This form of projectile would also break up in a severe attack, but generally only after making a hole in the plate (the hardness at the tip and shoulder was too high and created brittle carbide networks). Such projectiles do generally attack the resistence of the plate to plastic deformation.
The US used initially APCBC-HE, but with softer nose and sheath hardening pattern.

Very generally, somewhat softer armor would be ideal for fighting UK/ US but it would be less capable to break up the blunt attacking large calibre soviet shells, which would have lowered resistence vs soviet guns. Perhaps, they could also have optimized against a shell which breaks up more easily than their own, but then again, such armor would be less ideally resisting high quality AP, which were assumed to be devloped anyways.

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by ThatZenoGuy » 23 Feb 2021 15:49

In regards to the Pzgr.39, I have heard that later war versions of such a shell existed that were more capable against sloped armor/general penetration. Is this true? From a logical standpoint they'd been fighting sloped armor tanks for a few years, and hence would start making shells to match their targets?

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by critical mass » 23 Feb 2021 19:28

The mid ww2 Pzgr.39 is the fairly close to a gold standart for full calibre AP-anti tank projectiles in ww2. The simple, decremental hardness pattern is on the sweet spot to resist change of shape but not breaking up. This sweet spot varied with projectile calibre and the dependencies were carfully worked out to improve mass produced shells. Development towards the end of ww2 increased the reliability of the fuze under acute oblique impact (grace action element) and by improving the proofing angle from 30°to 45° (against German RHA) with little change in penetration, except that the shell is likely to stay intact more while attacking highly oblique. The shell exploited both, the HHA of SU AFV by lower energy adiabatic shear failures (associated usually by an intact shell driving out a plug) and the very soft cast or RHA of US AFV in particular (lack of resistence to plastic deformation against an intact penetrator). The projectile had little effect on British RHA, which while varying in quality was having not too dissimilar hardness properties as German RHA (depending on section thickness, ofc).
The Pzgr.39 was the only ww2 projectile -to my knowledge- which could be dependet upon to burst after penetrating a severe target at high velocity and moderate obliquities in effective bursting condition. Soviet projectiles generally deformed and borke up, even while striking <1^cal/D at normal. This usually split up the projectile body or rendered the fuze container dysfunctional. At best the burst is just 1/3 as powerful or blind. At worst, the large HE filler may contribute to reduced penetration by exploding low order while still outside the armor before the projectile succeeded in making a hole, cutting penetration potential (i.e. the causal reason for having the -SP of the AP-proectiles variants issued).
For this reason, the british deleted HE-filler entirely, relying on AP-shot. The US 76mm and 75mm APCBC-HE projectile could stay intact much better than the soviet ones, but only at rather low terminal velocities and low obliquity (<25-30°). The rather softer, sheath hardened projectiles, a hardness pattern closely resembling that of contemporary major calibre naval AP projectiles, contributed in shatter suspectability.

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by ThatZenoGuy » 24 Feb 2021 04:22

*Wishing War Thunder would account for any of this*

Very interesting information however! Was the HE payload truly worth it?

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by critical mass » 24 Feb 2021 09:20

Not in terms of blast effect. The small % HE filler of German 5.0-8.8cm Pzgr. 39 was labelled as a "Zerleger". Although blast is amplified in confined spaces, it will not greatly contribute other than breaking up the thick walled AP-projectile in a smaller number of large fragments, which are still lethal to everything they encounter within the short distances, encountered in AFV spaces. Fragmentation pattern ivolved here typically a large nose piece moving along the trajectory and several lateral and base pieces moving along perpendicular arcs to the trajectory. They will only be reflected by thick enough armor plate but then move along unpredictably, shedding more and more energy with every passage / reflection.
This fragmentation occurs after penetration, is independent of residual terminal velocity and, thus greatly increasing the chance to hit something relevant within the tank.

Now of course, a broken up AP-shot will also do this without any HE-component present. This, however, comes with some disadvantages.
I) if the break up occurs before completing the penetration of the target plate, only a % of those fragments (moving closest along the trajectory) will enter the AFV, with a number of lateral and base fragments beeing shielded from entering the AFV. Additionally, the broken penetrator is less dense and suffers therefrom by reduced penetration to start with, which is an undesirable feature. A fully shattered shell will mostly sent fragments perpendicular to the trajectory, and most fragments, safe some small nose pieces avoid entering the AFV, whether or not the energy was sufficient to make a hole in the first place.
II) if the break up occurs after the penetration, this implies a small degree of breakage and deformation of the projectile, so fragments move closer along the trajectory through the AFV with practically no perpendicular fragment spread unless the plate added this component. The energy delivered is directly linked to the residual terminal velocity of the shell (i.e. the remianing velocity AFTER penetration), which will be very low for high quality AP-shots, requiring targets severe enough to actually break up a projectile, but higher for low quality AP (less target thickness is required to break up the shell), in the latter case the fragment velocity is higher but fewer % break up after penetration (see I). For example, British AP-shot breaking up naturally after making a hole through a severe target (low cal/D, say 17pdr AP-shot vs TIGER-I front from close range and medium obliquity) would send fewer fragments along a narrow cone through the AFV. Against a light target (high cal/D, say 17pdr AP-shot vs Pz-IV side), the projectile stays whole and may just exit the other side (this event is still deadly, of course, for everything along the projectiles trajectory sinde the AFV).

The small % HE filler gets the best of both worlds: It does not degrade AP-penetration while penetrating and also gets a very wide cone of fragments after penetration, whether or not the target plate is thick or thin (ok within some limits as very thin plates may be thoroughly overmatched or may not be strong enough to activate the delay fuze). At least for targets below, say 40-55° (depending on thickness and hardness), where reliable action can be expected. At more acute angles, or against harder and thicker plates, the Pzgr.39 also breaks up, resulting mostly in a dud (the most damage / deformation is at the base while penetrating high oblique targets), with the HE-filler, if it undergoes a low order detonation, will not be powerful enough to fragments the steel body. Breakage occurs here from penetration, assisted by plate fragments or plugs ejected perpendicular from the plate (particularely from plates with higher hardness). Because post ww2, everyone employed highly sloped surfaces, the HE filler became ineffective and was dropped.
Late ww2 German research on a new Pzgr. with hemisspherical head and different cap for enhanced high oblique penetration against cal/D targets in the range of 50°-65° (probably comes with reduced penetration at low obliquity) was never completed -to the best of my knowledge- due to difficulties of fitting the AP-cap robustly enough on the shorter projectile contact surface with solder (Unlike the british and US, the German Army and Navy projectiles didn´t used crimps as AP attachment because they would always remain as weak points on the projectile nose, allowing stress zones to occur, where fragmentation or shatter will originate from earlier) and due to the performance to make a hole through not beeing much better (the projectile stayed intact and also perforated at much lower velocity but the broken up series Pzgr.39 could hole such a target (not penetrate, and not effective) just fine.

whether or not Warthunder relates to this is not relevant. At leas to me. They are a gaming enterprise and should be free to do whatever they want.
Last edited by critical mass on 24 Feb 2021 11:50, edited 1 time in total.

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by ThatZenoGuy » 24 Feb 2021 10:42

critical mass wrote:
24 Feb 2021 09:20
whether or not Warthunder relates to this is not relevant. At leas to me. They are a gaming enterprise and should be free to do whatever they want.
Well, they are supposed to be historically accurate, so stuff like that always needs to be under consideration. ;D

I believe the Soviets used APHE far into postwar, such as the Object 279?

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by critical mass » 24 Feb 2021 11:29

This is correct. They used APHE in post war times. Its still a useful projectile if it engages light AFV armor (not strong enough to break up the shell) or softer hardness grades, which does not break up the shell nearly as bad as German RHA did. Also, when engaging highly sloped plate, it would break up, but so would other projectiles. If the filler is small enough, it will just blow the tail out, not fragment the projectile). At low obliquity, the blunt nosed or uncapped pointed ww2 projectiles were obsolete, though.
However, after the GPW, the Soviet Union also introduced a reverse engeneered Pzgr.39 APCBC-HE for its entire range of 57-130mm tank and anti-tank guns postwar (UBR-367, BR-412D, BR-471D, UBR-472 and BR-482B(?), for the entire range of their new 57-130mm calibre tank and anti tank guns) in a major AP-ammo update program, exploiting the spoils of war (this involved disassembling whole ammo factories with experience in Pzgr.39/42 production within the terretory of the soviet occupational zone of Germany and their replacement to the Soviet Union, along with technical personal). The new soviet familiy is not a clone but a close adaption of the German Pzgr.39/42 (same fuse, similar He cavity, nose and cap shape as well as its attachment with solder rather than crimps used by the US and british Armies, even the windscreen, steel mix and hardness pattern closely followed it) introduced in the early 1950´s.
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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by ThatZenoGuy » 01 Mar 2021 16:42

So it seems the Pzgr 39 (and its updates) were almost the perfect design for an APCBC shell?

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by critical mass » 02 Mar 2021 10:44

I doubt there is something "perfect". If that would be the case, the Germans themselve wouldn´t invest so much effort to further improve the projectile. Speaking strictly from an engeneering point of view, much is a compromise between conflicting requirements. But it probably helped a lot that they explored and understood the cross relationships between target hardness, projectile hardness pattern and calibre, brittleness and failure modes and succeeded in applying these results in mass production technique (which by its own is no small feat).

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by AKahl » 21 Mar 2021 19:38

Thanks to OP and critical Mass for addressing this subject. I also saw the video with Hillary Doyle and Chieftain, and couldn't believe that the frontal armor of the Hetzer was only equal to an armored car or half track. I think you've pretty well put it to rest, at least to my satisfaction. It seems that they wouldn't have gone to such trouble to slope the front glacis plate, and in fact the whole vehicle, only to then make it out of the ballistic equivalent of cheese.

Obviously it's an imperfect vehicle, with a lot of defects, but it was cheap, and a pretty resourceful use of an obsolete chassis.
Remain yourself, in spite of all the mighty do.

Goethe

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by ThatZenoGuy » 28 Mar 2021 13:11

Yeah thanks Critical Mass for the great information, I highly appreciate it.

However I am curious on if the claims of the side armor being of lower quality is true. It's sourced by the same guy as far as I am aware of, who has already been wrong once (accidentally of course).

So who knows? Anybody got a clue?

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by Yoozername » 28 Mar 2021 19:15

ThatZenoGuy wrote:
24 Feb 2021 10:42
critical mass wrote:
24 Feb 2021 09:20
whether or not Warthunder relates to this is not relevant. At leas to me. They are a gaming enterprise and should be free to do whatever they want.
Well, they are supposed to be historically accurate, so stuff like that always needs to be under consideration. ;D

I believe the Soviets used APHE far into postwar, such as the Object 279?
On a similar note, the people that make Combat Mission feel the same way.

I see T34/85, using 1945 ammunition, poke holes through Panther glacis at 1000 meters and a side angle to boot. This is apparent in a scenario titled "The Myth of Invincibility'! The designers clearly have a bias IMO.

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by Yoozername » 28 Mar 2021 19:22

critical mass wrote:
02 Mar 2021 10:44
I doubt there is something "perfect". If that would be the case, the Germans themselve wouldn´t invest so much effort to further improve the projectile. Speaking strictly from an engeneering point of view, much is a compromise between conflicting requirements. But it probably helped a lot that they explored and understood the cross relationships between target hardness, projectile hardness pattern and calibre, brittleness and failure modes and succeeded in applying these results in mass production technique (which by its own is no small feat).
The PzGr 39 design was basically a reaction to two very different AFV...namely the T34 and KV-1. It just so happened to work against many other AFV. But I would agree that it was an effective engineering effort and I am surprised that it was not copied by the US at least. The US studies showed it to be superior.

And I agree that using the word "perfect" has no real meaning.

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Re: "Hetzer" (Jagdpanzer 38) Armor Quality, allegedly 50% the value of RHA?

Post by Peasant » 29 Mar 2021 07:38

Yoozername wrote:
28 Mar 2021 19:22
critical mass wrote:
02 Mar 2021 10:44
I doubt there is something "perfect". If that would be the case, the Germans themselve wouldn´t invest so much effort to further improve the projectile. Speaking strictly from an engeneering point of view, much is a compromise between conflicting requirements. But it probably helped a lot that they explored and understood the cross relationships between target hardness, projectile hardness pattern and calibre, brittleness and failure modes and succeeded in applying these results in mass production technique (which by its own is no small feat).
The PzGr 39 design was basically a reaction to two very different AFV...namely the T34 and KV-1. It just so happened to work against many other AFV. But I would agree that it was an effective engineering effort and I am surprised that it was not copied by the US at least. The US studies showed it to be superior.

And I agree that using the word "perfect" has no real meaning.
According to post war US studies comparing the effectiveness of capped vs monoblock AP the former is better when attacking highly oblique targets, at 55° and over, albeit at the expense of performance at low obliquity against very thick targets. Considering that the new generation of post-war tanks all had a highly sloped armour, the decision to go with monoblock AP for their guns is logical.

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