Allied tank armor, quality control

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Mobius
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Re: Allied tank armor, quality control

Post by Mobius » 08 Apr 2019 16:59

I haven't seen an direct German evidence that they used 7.5 cm KwK 40 with the K.Gr.rot projectile it's not that it was impossible to substitute it. The Allies did use the K.Gr.rot on their 75mm AP.

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Re: Allied tank armor, quality control

Post by Yoozername » 08 Apr 2019 17:30

Mobius wrote:
08 Apr 2019 16:59
I haven't seen an direct German evidence that they used 7.5 cm KwK 40 with the K.Gr.rot projectile it's not that it was impossible to substitute it. The Allies did use the K.Gr.rot on their 75mm AP.
IF the Germans DID use it, then how would there be such an acute shortage of armor piercing ammunition in 1942? I would expect that IF the Germans did have existing production of that K.Gr.rot projectile, and it would then be a matter of just manufacturing the longer 'brass'. Basically discontinuing AP for the L24 weapons, and having them rely on HL rounds and HE.

Mobius and I have been going on about this for some time? Haven't we?

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Re: Allied tank armor, quality control

Post by peeved » 08 Apr 2019 19:55

Mobius wrote:
07 Apr 2019 19:54
I'm not sure what the Gr. 38 rot is.
3/1942 is long after the Gr. 38 hl/A was introduced.
Maybe Gr. 38 rot and the Soviet tests' m.38 are similar overgeneralisations to the ones in this doc from http://www.panzer-war.com/page48.html Image
i.e. using Pak 38y nomenclature; Pzgr.Patr. 38 KwK; for 7,5 cm KwK ammunition. The table goes one step beyond though in listing several fixed ammunition types as projectiles.
The Soviet tests' m.39/40 also might derive from a cartridge designation, e.g. Pzgr.Patr. 39 KwK [or Pak] 40. Note how two KwK cartridges are listed as Pak 40 projectiles in the table.

Markus

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Re: Allied tank armor, quality control

Post by Mobius » 08 Apr 2019 23:22

peeved wrote:
08 Apr 2019 19:55
The Soviet tests' m.39/40 also might derive from a cartridge designation, e.g. Pzgr.Patr. 39 KwK [or Pak] 40. Note how two KwK cartridges are listed as Pak 40 projectiles in the table.
Markus
You may be right. I thought it might mean Pzgr.Patr. 39 or 40 but it may be more likely meant to designate the 7,5cm KwK 40 (or PaK 40) Pzgr.Patr. 39 as opposed to 5 cm Pzgr.Patr. 39 from KwK 39 (Or PaK 39).

As CM pointed out.
A different picture is observed when inside almost empty tank a high explosive part of 75mm armor-piercing shell with red ring {80 grams of TNT with detonator of 20 grams of PETN/wax} is bursting.
The Pzgr.Patr. 39 does not have 80 grams of burster. That honor goes to the K. Gr.Pz.

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Re: Allied tank armor, quality control

Post by Avalancheon » 09 Apr 2019 02:35

Peasant wrote:
30 Mar 2019 18:39
On the topic, I have found some intresting data today:

Image
Are these the results of actual ballistic tests, or just calculations? The table suggests that the 6 pdr gun could only penetrate the Shermans glacis from 180 to 300 yards. This is very surprising. In the Tunisian tests, the 6 pdr gun succeeded in penetrating the glacis of a Tiger from 600 yards (albeit only with 1 shot out of 8).

Given the difference in T/D ratios, how can the Shermans armor be offering better protection than the Tiger?
Peasant wrote:
30 Mar 2019 18:39
The most striking part is the sudden change in resistance between 2in./45° transmission cover and the 2in./56° glacis plate. They may've shot themselves in the foot when they switched to the 47° glacis in the later versions.
The M4A3 Shermans with their 63mm thick 47 degree glacis offered greater protection than the earlier Shermans with 51mm thick 56 degree glacis. In theory, they actually would have been able to withstand hits from 75mm Pzgr. 39.

viewtopic.php?p=2191974#p2191974

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Re: Allied tank armor, quality control

Post by Yoozername » 09 Apr 2019 03:25

Are these the results of actual ballistic tests, or just calculations? The table suggests that the 6 pdr gun could only penetrate the Shermans glacis from 180 to 300 yards. This is very surprising. In the Tunisian tests, the 6 pdr gun succeeded in penetrating the glacis of a Tiger from 600 yards (albeit only with 1 shot out of 8).
My impression is that they did a shoot on a sherman with the 2 pdr. and 6 pdr. guns. They then extrapolated the effects that the various other guns would have. Basically, using whatever known penetration values they had.

I am surprised no one else thinks the US 90mm firing the M77 ammunition is not 'immune'.
The Isigny test No. 2
8) 90mm Gun, M1A1, AA
AP M77 will penetrate front glacis slope plate up to 600 yards, the gun mantlet up to 1,000 yards and the turret up to 1,500 yards.

This gun also had the effects of its HE round tested, demonstrating the processes by which non-penetrating hits by heavy HE could damage a tank’s armor:

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Re: Allied tank armor, quality control

Post by Avalancheon » 09 Apr 2019 04:41

Yoozername wrote:
09 Apr 2019 03:25
My impression is that they did a shoot on a sherman with the 2 pdr. and 6 pdr. guns. They then extrapolated the effects that the various other guns would have. Basically, using whatever known penetration values they had.
That is a very surprising result for me. I would never have thought that the Shermans glacis would offer better protection than the Tigers glacis. Perhaps it has something to do with the design of the 6 pdr shells? Maybe they just can't handle sloped armor... I imagine we would see very different results if a 75mm gun were used instead!
Yoozername wrote:
09 Apr 2019 03:25
I am surprised no one else thinks the US 90mm firing the M77 ammunition is not 'immune'.
The Isigny test No. 2
8) 90mm Gun, M1A1, AA
AP M77 will penetrate front glacis slope plate up to 600 yards, the gun mantlet up to 1,000 yards and the turret up to 1,500 yards.

This gun also had the effects of its HE round tested, demonstrating the processes by which non-penetrating hits by heavy HE could damage a tank’s armor:
Nice catch, I didn't notice that part. This too is very incongruous with what we know about the guns in question. If its true that the 90mm gun wasn't actually fired at the Sherman (as you say), then they must have just done an estimation. A very mistaken estimate, as it turns out.

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Re: Allied tank armor, quality control

Post by Yoozername » 09 Apr 2019 14:18

The M77 was a basic solid penetrator. The sherman armor is relatively soft, it should have been no problem.

http://uxoinfo.com/blogcfc/client/inclu ... rd_Id=P119

Image

Image

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Re: Allied tank armor, quality control

Post by Mobius » 09 Apr 2019 15:08

If you really want to find what the penetration of the M77 is you can use the fact that the T33 is basically a M77 with a ballistic cap. N4636C2 Terminal Ballistics data 1945 vol. III part2 has a graph of the T33 with a 55° and 30° penetration scale. Then use that striking velocity to see what range that velocity is at in the M77 graph in A955369 Handbook of Ballistic and Engineering Data Vol 2 1950. A bit of a round about way. The good part is the US penetration tables are tested on Sherman like armor.

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Re: Allied tank armor, quality control

Post by critical mass » 09 Apr 2019 15:35

Yoozername wrote:
08 Apr 2019 12:54
75mm K.Gr.rot Pz. was to be fired from all StuK and KwK40.
So, to be clear, you are saying that the high velocity weapons, that is the KWK 40 (L43 initially) and StuK 40 (L43), which were designed at the same time as the Pak 40, were to use a different armor piercing projectile design? That is, The Pak 40 would use the Pzgr 39, and the KWK/StuK weapons were to use the same projectile as the earlier KWK 37/StuK 37? You are not speculating that the Germans, who clearly had issues manufacturing the Pzgr 39 in the quantities needed in 1942, might have tried a 'substitute standard, such as using the earlier large capacity AP as a temporaneous solution; You are actually stating they designed the KWK 40/StuK 40 to fire it? How can you explain the report from summer of 1942 that I posted? The Germans are clearly issuing SOP as far as how/when to fire the armor piercing ammunition. They haven't fielded great numbers of Panzer IV F2 (G) or StuG III F at this time. It is actually quite low.

I am not commenting on whether or not we are justified to call the K.Gr. rot Pz. a substitute standart. In my opinion, that remains a viable possibility, but one which needs confirmation from sources to be acceptable. At one point in the design & devlopment (and even early fielding..) process, these guns were not planned for with Pzgr.39. That´s nothing very special. When the 5cm PAK38 was conceived and tested in 1939, only the uncapped 5cm Pzgr Gg existed, not the capped 5cm Pzgr.39 (Of course, the PzgrGg was not up to the task required, due to the high velocity and eventually was replaced by a new welded design, the starting step of the Pzgr39 development). At one point, decisions were made to change that, and this is stated to be a response to the advent of more heavily armored tanks (Char B1 for the PAK38 and KV1 for the PAK40). However, I have not researched the K.Gr. rot Pz. projectile yet. You know that I have focussed on the Pzgr.39 development in the limited time I have at my diposal to pursue these questions.
When the early model KwK40 and StuK40 (L/43 models) were first issued to the front, the 75mm Pzgr.39 was still undergoing it´s testing stages at Hillersleben. Initial batches of Pzgr.39 went to PzJäger issued with the new PAK40. So what did the StuK and KwK fire then? You will note,if You pay attention, that the 75mm K.Gr.rot Pz. had it´s service penetration curves at 30° (!) drawn up to 700m/s terminal velocity, but not much further. This is far in excess of what would be required from a projectile to be fired from a low velocity L/24 howitzer guns but it is in agreement with early L/43 weapons, very approximately.The soviets apparently in late 1943 still had access to red ringed A.P. with 80 g high explosive to be fired from model 40 gun (unknown whether PAK40, StuK40 or KwK40). How long they kept those stored away after capture remains unknown. Unless You imply some sort of experimental ammunition, -for which we have no evidence- this is an accurate description of the 75mm K.Gr.rot Pz.
As You have correctly deduced, there was an acute shortage of Pzgr.39 reported for 1942. That does not equate a general shortage of A.P., though the manufacturing pace was indeed slow -but a shortage of the preferred new A.P. model, the much more effective Pzgr.39.


---
Shouldn´t the 90mm M77 should have little problems defeating 51.8mm cast armor at 60°?

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Re: Allied tank armor, quality control

Post by Yoozername » 09 Apr 2019 15:58

I am not commenting on whether or not we are justified to call the K.Gr. rot Pz. a substitute standart. In my opinion, that remains a viable possibility, but one which needs confirmation from sources to be acceptable.
No, you commented this....
75mm K.Gr.rot Pz. was to be fired from all StuK and KwK40.
Basically, you are just trying to say you don't really know? That you are assuming, and it isn't really backed by data?

But we agree, it needs more information.

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Re: Allied tank armor, quality control

Post by Mobius » 09 Apr 2019 16:06

BTW M77 is not an A.P.H.E. round. It is AP. So the M82 round should be the one looked at.

Another point.
There's a strange passage in the book German Anti-tank Troops in World War II.
The situation had to embitter the awaited delivery of the guns in May and June. A special problem under the code name of "Ullrich" was to help out; it's goal was a considerable increase in the production of armor-piercing ammunition. The preparations for the realization of this program began with the involvement in July 1942 of Rerich Minister for Armament and Ammunition Fritz Todt. An easing of the tense ammunition situation took place only in 1943
I think they got the word "program" mixed with "problem", but it doesn't say what the program was.

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Re: Allied tank armor, quality control

Post by Yoozername » 09 Apr 2019 17:20

BTW M77 is not an A.P.H.E. round. It is AP. So the M82 round should be the one looked at.
Not for the test on the Panther
The Isigny test No. 2
8) 90mm Gun, M1A1, AA
AP M77 will penetrate front glacis slope plate up to 600 yards, the gun mantlet up to 1,000 yards and the turret up to 1,500 yards.

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Re: Allied tank armor, quality control

Post by critical mass » 09 Apr 2019 17:58

Yoozername wrote:
09 Apr 2019 15:58
I am not commenting on whether or not we are justified to call the K.Gr. rot Pz. a substitute standart. In my opinion, that remains a viable possibility, but one which needs confirmation from sources to be acceptable.
No, you commented this....
75mm K.Gr.rot Pz. was to be fired from all StuK and KwK40.
Basically, you are just trying to say you don't really know? That you are assuming, and it isn't really backed by data?

But we agree, it needs more information.
No, I do not assume anything, except that in lack of evidence to the contrary, I presume that the people can be expected to follow default practices. The Panzermuseum Münster explicitely states, that the 75mm K.Gr.rot Pz. was to be fired from all StuK and KwK40 on the display of the 75mm K.Gr. rot Pz. with long and necked cartridge for either KwK or StuK (PAK had the sleek, unnecked long cartridge). I have no reason to doubt that or to presume that the kurators somehow managed to make up the shell and cartridge. Similarely, I have no reason to presume the soviets used experimental ammunition instead of captured service ammunition in their tests.
For me, actually, the notion that the StuK40 and KwK40 fired only Pzgr.39 A.P. from the start is the notion which is not believable. I have the test documents here and can assure You that when the first F/2 reached the fronts in summer 1942, this projectile was still undergoing its final standartization, and that´s before mass production commences.

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Re: Allied tank armor, quality control

Post by Yoozername » 09 Apr 2019 18:23

Ok, you are basing this on something painted in a museum. Thanks.

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