The Russians test the Pak 38 and its PzGr 39

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Re: The Russians test the Pak 38 and its PzGr 39

#16

Post by Yoozername » 08 Sep 2017, 21:19

I was mostly pointing out the Soviet test methodology....from the OP
Here are results of the spring 1942 testing of a captured German gun and its AP rounds, firing at 45 MM plate with HB 450+/- 40, as for the T 34 glacis. (A total of six regular APC, APBC and APCR projectiles were tested, I mention two of them).
At 0 degrees total deflection of 45 mm plate: PTP 363 m/s, PSP 415 m/s. 15 degrees 375/465 m/s, 30 deg. 411/539 m/s, 45 degrees 613/770 m/s, 60 deg. 809 m/s PTP no PSP penetration.

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Re: The Russians test the Pak 38 and its PzGr 39

#17

Post by Mobius » 09 Sep 2017, 17:56

Here's a Russian document on that subject.
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50mm Pak38 Rus.jpg


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Re: The Russians test the Pak 38 and its PzGr 39

#18

Post by Christian Ankerstjerne » 12 Sep 2017, 19:29

Mobius wrote:Why doesn't the table data reflect this penetration plateau? It shows a 67mm penetration instead of the 56mm from the graph.
http://www.panzerworld.com/5-cm-pak-38

Here is a Impact velocity table of the 50mm/L60 APC
50mmL60APC.jpg
Those numbers match the German firing table quite closely:

200 m: 783 m/s
500 m: 707 m/s
1000 m: 591 m/s
1500 m: 491 m/s

The penetration data on my website for the Pzgr. 39 also matches the data in the German firing table.

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Re: The Russians test the Pak 38 and its PzGr 39

#19

Post by Mobius » 12 Sep 2017, 21:41

Christian Ankerstjerne wrote:
Mobius wrote:Why doesn't the table data reflect this penetration plateau? It shows a 67mm penetration instead of the 56mm from the graph.
http://www.panzerworld.com/5-cm-pak-38

Here is a Impact velocity table of the 50mm/L60 APC
50mmL60APC.jpg
Those numbers match the German firing table quite closely:

200 m: 783 m/s
500 m: 707 m/s
1000 m: 591 m/s
1500 m: 491 m/s

The penetration data on my website for the Pzgr. 39 also matches the data in the German firing table.
That's little different than the firing table data I have:
50mm/L60 APC
0m: 835 m/s
100m: 809 m/s
500m: 706 m/s
1000m: 590 m/s
1500m: 489 m/s

Could your data be for the Pzgr. 38 AP?

Still I could of done a better job of adjusting the ballistic coefficient until they matched.
should be able to locate on page 89.
http://www.lexpev.nl/downloads/handbuch ... 361945.pdf

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Re: The Russians test the Pak 38 and its PzGr 39

#20

Post by Christian Ankerstjerne » 12 Sep 2017, 23:00

It refers specifically to the 5 cm Pzgr and 5 cm Pzgr 39, with a muzzle velocity of 835 m/s, and a weight of 2.06 kg, from the April 1943 version of H. Dv. 119/313.

I would venture to say that the difference is smaller than for what the altitude, temperature, and humidity would account.

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Re: The Russians test the Pak 38 and its PzGr 39

#21

Post by Mobius » 13 Sep 2017, 02:16

Christian Ankerstjerne wrote: April 1943 version of H. Dv. 119/313.
.
Which I would take as a primary source.

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Re: The Russians test the Pak 38 and its PzGr 39

#22

Post by Miles Krogfus » 17 Sep 2017, 20:35

Here are 3 pages from the DHHV daybook with data from the Metallurgic Quality Control Department. The "Sicher" or 'safe' range of German armor plate of different chemical contents tested by 50 mm AP did not change from 1942 to 1945. The Nov.1942 TL 4033 curve for uncapped AP (not from DHHV) is a draft version with different AP weight and velocity than later shown on German documents. DHHV page 700 has an August 25,1942 test graph, using 50 mm AP. DHHV page 1355 has the April 19,1943 data showing Sicher thickness of plates tested by various mm of all types of AP : plates 7 to 100 mm. thick.
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dhhv 4 001.jpg
dhhv 3 001.jpg
dhhv 2 001.jpg
dhhv 1 001.jpg
Last edited by Miles Krogfus on 18 Sep 2017, 09:09, edited 1 time in total.

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Re: The Russians test the Pak 38 and its PzGr 39

#23

Post by Miles Krogfus » 18 Sep 2017, 00:07

Two more pages from the April 19,1943 DHHV document:
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dhhv 1a 001.jpg
dhhv 2a 001.jpg

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Re: The Russians test the Pak 38 and its PzGr 39

#24

Post by Miles Krogfus » 19 Sep 2017, 01:26

This extract from DHHV page 696 shows the results of the 50 mm uncapped AP firings diplayed on page 700 above. The February 1945 50 mm uncapped AP curve shows that with such 60-110 mm panzer plate as listed on page 696, even with revised chemical contents, there was no late war lessening of penetration resistance allowed producers.
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page 1 001.jpg
page 2 001.jpg

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Re: The Russians test the Pak 38 and its PzGr 39

#25

Post by Mobius » 23 Sep 2017, 17:28

How are the Germans calculating the energy in these graphs or on tables in http://www.lexpev.nl/downloads/handbuch ... 361945.pdf?
Shouldn't mkg be joules?

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Re: The Russians test the Pak 38 and its PzGr 39

#26

Post by Stiltzkin » 24 Sep 2017, 02:48

How are the Germans calculating the energy in these graphs or on tables in http://www.lexpev.nl/downloads/handbuch ... 361945.pdf?
Shouldn't mkg be joules?
It is in Meterkilogramm , the Energy to raise an object of 1 Kilo weight by 1 meter (1 to 0,102, or 1 J = 1 Kgm²/s²)= 9,81 Nm or 9,81 Joule. Just multiply with 9,81 to get in J.

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Re: The Russians test the Pak 38 and its PzGr 39

#27

Post by critical mass » 28 Sep 2017, 13:50

The charts provided by Miles show service acceptance conditions for armor plate. The test projectile in this case was not the 5.0cm Pzgr but the decapped 5.0cm Pzgr.39 (notice the difference beyond presence / absence of the cap in the differing heat treatments and "welded on tip"!).


Notice that the data in these tables refer to protection limit (Gs), not perforation limit (Gd). Of course, while the AP-maker would be interested to know what kind of penetration could be expected by his product, the armor maker would be interested on what kind of protection his product provides for.
WaPrüf6 issued a number of these "protection limit" graphs, of which I attached one to show the ratio for various calibres in this memo.
The procedure differed from AP-explorative trials in that
[+] velocity was constant (at 100m distance for 2.0cm and up)
[+] the obliquity was started at 60°, 45° or 30°, depending on plate thickness and so much changed in steps of 2.5° each after each set of, say 5 shots, until complete protection was obtained by the plate. Examples of the reults can be viewed in Miles attachments above.
[+] "Ballistic Protection" was obtained when the backside of the plate only showed smooth bulging but no complete cracking through (light shall not pass) a disc/ plug started was ok, but disc/plug ejected was a failure
[+] Plate failure (cracking through, excessive plugging / discing) will reject the plate. Discing itselfe was not considered a problem -unlike US/British practices- when it had the same high critical velocity, but plugs beyond 2 to 2.2 times the attacking calibre diameter indicated shear sensitive problems with the armor and thus might also lead to a poor resistence vs intact, pointed projectiles.

The use of decapped AP for test of homogenious armor was rational for a specific reason. Decapped AP would -at least at high impact velocities- break up or deform on plate impact, creating a blunt nose for penetrating attempt. Such blunt noses will show defects of armor in shear strength more readily than pointed noses because the principle failing of blunt nose penetrators is tied to adiabatic shear failure vs ductile hole formation in case of intact pointed projectiles. Plugs and discs were considerably smaller with capped AP than with uncapped AP. The use of uncapped AP therefore constitutes a more severe test of the armor material in regard to exposure of the materials shear failure.
Notice that this was important for german homogenious armor due to their preference of more harder / more brittle armor plate at the ductile/ brittle first transition. Also, "lean" armor with lower alloying content tended to have significantly narrower bandwidths between the different failure modes than more "fat" armor with higher alloying content, as could be expected.
One of the charts show that against vertical impact (normal to the perpendicular), the limit for protection against 5.0cm decapped Pzgr.39 was about 80mm Wh, while the capped Pzgr39 would be resisted fully only with a 90mm Wh plate. The difference is not only related to the the different failure mechanisms involved in whether or not the plate fails by ductile hole formation or plugging. Also the projectiles behave differently. While the uncapped projectile undergoes nose damage and blunting, the penetration energy is spread out over more initial contact area (less focussed) while the capped AP keeps the nose shape of the Pzgr 39 intact at such impact velocities (ca. 810m/s in this case) and allows penetration at lower residual kinetic energy because it is focussed more. Lower energy penetration of course translates into a thicker plate beeing needed to stop said projectile in the first place.
It appears from the data that only partial nose break up occurs with the two piece 5.0cm Pzgr 39, probably enticed by the welded on tip. The old uncapped, monobloc 5.0cm Pzgr could reliably defeat only ca. 58mm Wh at 30°at 820m/s and hardly more than 60mm at normal due to complete break up at these velocities.
However, at low velocities (below 600m/s), where neither projectile suffers by break up effects, the old, uncapped monobloc design was better because it didn´t waste any weight for the cap.

Notice that cast homogenious armor plate offered ca. 20% LESS resistence vs uncapped 5.0cm Pzgr 39 at normal impact and ca. 40% LESS resistence to it in oblique impact. Therefore 100mm cast armor offer just enough resistence to keep out 5.0 cm Pzgr 39 o.K. (without cap) at normal and 90mm cast at 45° where 80mm RHA and 70mm RHA, respectively, would suffice.
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protection_limit_armor_acceptance.jpg
Last edited by critical mass on 28 Sep 2017, 17:31, edited 2 times in total.

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Re: The Russians test the Pak 38 and its PzGr 39

#28

Post by critical mass » 28 Sep 2017, 13:58

Mobius wrote:Here's a Russian document on that subject.
It´s calculated data, not tested. Therefore, You cannot possibly see differences between 5.0cm Pzgr and 5.0cm Pzgr 39. Both had the same weight and therefore also have the same residual kinetic energy when calculated. The constant De Marre K=2400 used here is describing typical soviet AP vs soviet armor interaction, and has no relevance with how german AP interacts with soviet armor.
I suspect that while the monobloc 5.0cm Pzgr would not be too different (due to projectile break up, at least at close range), the capped 5.0cm two piece Pzgr 39 has be expected to vary significantly from the tabulated data given therein.

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Re: The Russians test the Pak 38 and its PzGr 39

#29

Post by critical mass » 13 Nov 2017, 19:21

It seems to me enlightening to shed some perspective on the soviet firing trials of german 5cm Pzgr referred to by Miles Krogfus.
The soviet research institute and ARTKOM used the De Marre nickel-steel formula to normalize their results. Because both, PSP and PTP have been identified in soviet trials and even plotted for various obliquities, it seems useful to compare their results with german official penetration data compiled by WaPrüf for this projectile. Because the projectile is identic, any variance between the results thus can be narrowed down to armor plate quality differences in resistence and different defintion of penetration.

German G(s) for 5cm Pzgr39 m.K. at 0°: 90mm RHA [100kg/mm²] at 810m/s (protection limit)
De Marre K=2100 for reliable (5/5), protection of plate (no hole through)
German G(d) for 5cm Pzgr39 m.K. at 0°: 90mm RHA [100kg/mm²] at 880m/s (5 consecutive penetrations)
De Marre K=2285 for reliable (5/5), complete and intact penetration at 0° obliquity

German G(s) for 5cm Pzgr39 m.K. at 30°: 60mm RHA [110kg/mm²] at 717m/s (protection limit)
De Marre K=2475 for reliable (5/5), protection of plate (no hole through)
German G(d) for 5cm Pzgr39 m.K. at 30°: 60mm RHA [110kg/mm²] at 780m/s (5 consecutive penetrations)
De Marre K=2695 for reliable (5/5), complete and intact penetration at 30° obliquity

According to Miles, the data for soviet trials vs their own high hardness armor was:

Soviet data for PSP (75%/80% penetration expectation):
0°: K=1752
15°: K=1964
30°: K=2275
45°: K=3250
60°: no PSP

Soviet data for PTP (protective limit of backside damage):
0°: K=1531
15°: K=1583
30°: K=1735
45°: K=2588
60°: K=3415

The differences are so stark, that one might be unable to explain whats going on here. May I ask Mr. Krogfus to check once again whether or not the data are correct? Usually, when I encounter such differences (roughly 1/3 lower effective resistence at normal impact for the soviet 45mm (BHN 316-356) RHA test plate) I suspect the involvement of some form of shatter effects but this has to be excluded here -at least for the 5cm Pzgr- because it is stated explicitely that the Pzgr39 curves are for intact ("heil") projectiles in G(d).
The only tentative interpretation I can come up so far, and that should be treated with due caution (let´s not forget, it´s only a limited sample size here), is that the soviet high hardness test plate gives way to the impact in some sort of catastrophic manner (plate shatter? adiabatic shear failure?) which makes it resist an intact penetrator roughly like a construction grade, mild steel plate, and not at all like armor steel -at least when striking 0° to 30°.
Against broken up penetrators or shattered projectiles, such as the soviet domestic BR240 series, it would gain 1/3 resistence back and behave much like normal armor steel. But if the plate doesn´t succeed in breaking up the shot, that armor won´t protect You.

This interpretation seems to find some confirmation in an apparent reduction of the quality difference between 0° impact and 30° impact. at between 40°- and 50° obliquity, both resistence curves may even fall together, if the extrapolation is to be believed. This is the range of obliquities, where the 5cm Pzgr39 cease to be indestructable and where projectile break up occurs on this projectile, too. Unfortunately, at high obliquity, projectile break up may improve penetration by inhibiting ricochet. Else, it cannot be excluded that the soviet domestic armor works particularely fine at high obliquity, too.
Attachments
5cmPzgr39.jpg

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Re: The Russians test the Pak 38 and its PzGr 39

#30

Post by critical mass » 29 Nov 2017, 15:19

NII48 test of 45mm soviet domestic armor as of T34 specifications vs german and soviet 37mm, 45mm and 50mm projectiles, CAMD RF 38-11355-776 (parts of this report were purposefully excluded from beeing published by E.E.´s tankarchives)

45mm soviet HHA domestic armor plate at 0° obliquity vs:

(45mm & 50mm in right field of drawing)
1-50mm Pzgr39 (V0:835m/s) PTP =2300 m (!)
2-50mm Pzgr39 (V0:835m/s) PSP =1930 m (!)
3-50mm Pzgr40 (V0:1200m/s) PTP =1400 m (my note: Pzgr40 St. due to the lack of tungsten noticed in this core)
4-50mm Pzgr40 (V0:1200m/s) PSP =1300 m (my note: Pzgr40 St. due to the lack of tungsten noticed in this core)
5 & 6 are 45mm domestic AP a PTP =200m

(german and soviet 37mm in left field of drawing)
1-37mm Pzgr (V0:740m/s) PTP = 700m
2-37mm Pzgr (V0=740m/s) PSP = not determined
3-37mm Pzgr 40 (V0:1037 m/s) PTP = 450m
4-37mm Pzgr 40 (V0:1037 m/s) PSP = 350m
5-37mm soviet domestic AP (V0:820m/s) PTP = 250m
6.37mm soviet domestic AP (V0:820m/s) PSP = 170m

45mm soviet HHA domestic armor plate at 30° obliquity vs:

1-50mm Pzgr39 (V0:835m/s) PTP =2000 m (!)
2-50mm Pzgr39 (V0:835m/s) PSP =1250 m (notice: this is not much different to the german 1000m at 30° for PAK38 & T34 sides)
3-50mm Pzgr40 (V0:1200m/s) PTP =800 m (my note: Pzgr40 St. due to the lack of tungsten noticed in this core)
4-50mm Pzgr40 (V0:1200m/s) PSP =600 m (my note: Pzgr40 St. due to the lack of tungsten noticed in this core)

PTP: Limit of protection (bulge in back with star cracks and/or plug started allowed, but no complete hole through) -roughly similar to german G(s) limit and the US protective limit
PSP: Hole =/> cal dimater completely through the plate, or projectile stuck in plate - roughly similar to german G(D) grenz limit and the US Army Ballistic limit

Attached are diagrams and terminal velocity curves as well as photo and drawing of the projectile tested.

High hardness MZ-2Z (IS-8S)relies entirely on it´s ability to completely break up the pentrator and is consequently very prone to failure by adiabatic shear when it does not succeed in breaking up the shell in the first place. Projectile failure was the common mode with the inferior domestic 45mm APHE and APBC-HE projectiles -those against IS-8S armor specifications were laid out for to resist- and might even reasonably be justified against early ww2 german, uncapped 37mm and 50mm projectiles. Soviet IS-8S quality, high hardness 45mm armor was effective in not only breaking up soviet domestic AP shell, but in reliably shattering it, much like face hardened armor would have done. The service acceptance specification for 45mm HHA plate was two shots of 45mm APBC calibre beeing resisted at 700-705m/s with the PTP limit (720-725m/s for PSP).
Once 50mm and 75mm capped Pzgr39 appeared, this armor resists with a significantly lower strength than 1930´s construction steel under conditions where the projectile cannot be shattered. Even mild steel would have offered similar reistence levels to MZ-2 against an unbreakable shell but even may have offered more ductility and shock resistence vs overmatching projectiles.
It´s really hard for me to understand how such inferior material could have been used for a long time in critical armor applications. At and after the end of ww2, the soviets finally changed on their own from high hardness to medium hardness armor specifications with good results.
However, the blind reliance on projectile break up effects (only achievable against the weak projectile quality of soviet domestic AP), goes some way to explain the misconceptions in the metallurgic understanding prevailing at this time about the effects of hardness on penetration on the soviet side and the lack of ballistic knowledge paying attention to fundamental differences in the correlation between hardness and resistence due to different armor penetration mechanics. Once their projectiles got better and better, the resistence offered by HHA went south. Already against the 5cm Pzgr39 from spring 1942, the resistence of 45mm IS-8S plate at low obliquities was worse than 1890´s period nickel-steel armor, which by the standarts of the 1940´s was, well, really bad.

Only at much higher obliquities, the differences in resistence against unbreakable shells between soviet and german armor vanish, when the 50mm Pzgr39 also get´s broken up by the effects of oblique impact. It may be reasoned that the soviets were rationally advised by adopting highly sloped armor layouts to minimize the poor ballistic resistence of their domestic armor material.
Attachments
nii48.jpg
5cmPzgr39_b.jpg
5cmPzgr39_a.jpg
50mm_pzgr39_vs_45mm_MZ2.jpg

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