Allied tank armor, quality control

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

Post by critical mass » 14 Apr 2019 16:35

This is not the earlierst source for 75mm lang. Dez. 1942 is too late. By winter 1942/43, Pzgr.39 procurement wasn´t a bottleneck anymore. The weapons were in service by spring and summer 1942 and You have to search for the 1941 and early 1942 issued pamphlets.

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Re: Allied tank armor, quality control

Post by Yoozername » 14 Apr 2019 17:34

No, you missed my point, earlier ammunition is usually listed. Do you have the patrone designation for this supposed round? I suppose you have the pamphlets? They aren't in the German Handbuch updates.

I can show that other weapons also had this 'back' listed ammunition. But I think the impetus is on you, to show that two weapons, that actually used the same barrel, were developed to counter the same threat, were to use different ammunition. Basically, you are claiming a museum trophy, that you even claim looks like a Pzgr 39, is what you are basing your thoughts on?
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Re: Allied tank armor, quality control

Post by Yoozername » 14 Apr 2019 17:47

Here is an example....the 88mm Flak 18/36 guns list two AP rounds...The KWK 36 guns do not have two rounds listed, but just the later round, mainly because they only used that round.

Note they list the older Pzgr Patr, in addition to the later Pzgr 39.
88.jpg
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critical mass
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Re: Allied tank armor, quality control

Post by critical mass » 15 Apr 2019 14:52

Yoozername wrote:
14 Apr 2019 17:47
Here is an example....the 88mm Flak 18/36 guns list two AP rounds...The KWK 36 guns do not have two rounds listed, but just the later round, mainly because they only used that round.

Note they list the older Pzgr Patr, in addition to the later Pzgr 39.

88.jpg
And yet, in this list 8.8cm FLAK ammunition (both Spgr and Pzgr) doesn´t show up. But we have evidence of it´s use by TIGER battalions through 1942 and early 1943 (I have posted the primary source quote somewhere on this board). FLAK ammunition was incompatible with KwK ammo, due to the different primer of the KwK ammunition but that doesn´t prevent them from using it with inlaid electric primers.

It´s not constructive to blame other people with the burden of proof when the significant question at hand, which I have reiterated above now multiple times was left readily without an attempt to provide a sincere answer: What kind of A.P. ammunition do PzIV lang used through 1942 when the Pzgr.39 only became aviable very late in 1942 in any quantity? What kind of A.P. ammunition did the KwK40 / StuK40 intended to use as long as therer was not a single 75mm pzgr39 around, in say, late 1941, when the guns were first tested? What kind of 75mm A.P. ammunition do You think the soviets used for their "cannon-40" which was an A.P. shell with a red ring and a charge of 80g high explosive?

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Re: Allied tank armor, quality control

Post by Yoozername » 15 Apr 2019 16:33

You have been shown German reports that contradict you. From June 1942.

You don't have any proof to back up your assertion. Leave it at that. I see badly painted ammunition in museums sometimes. I wouldn't claim it is a source, but you did.

You can take constructive any way you want. But in the real world, you make an assertion, then back it up. You said you thought that a museum made a claim and that is good enough for you.
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Re: Allied tank armor, quality control

Post by Yoozername » 15 Apr 2019 16:55

Die Produktion der Munition, die aus den kurzen 7,5-cm-Kanonen verschossen werden konnte (in 1.000 Schuß):

7,5-cm-KwK-Granate

1939
432,9

1940
1.736,1

1941
877,9
This is the production of 7,5 cm L24 ammunition for the years leading up to 1942 change over. Considering this would only supply Panzer IV kurz and StuG III kurz, both of which were not manufactured/fielded in great quantities, and had reached rather depleted levels by early 1942, shows that there is a great means to manufacture 7,5-cm-KwK-Granate projectiles. So, why would there be any ammunition shortage for the Panzer IV F2, or StuG III F, as mentioned in the report in summer 1942? In fact, the ramp up of fielding these two new AFV was actually very slow, as was the production.

Initial German reports were very glowing on the performance of the L43 weapons. I guess a look into the possibility of the 7,5-cm-KwK-Granate performing at the higher velocities would be in order.

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Re: Allied tank armor, quality control

Post by Yoozername » 15 Apr 2019 17:17

One of the big issues, that also was mentioned before, is that the velocities that the new 7,5 cm weapons were achieving with Pzgr 39, would be incompatible with the earlier round.

Image

After 650 M/s, it is failing against 30 deg sloped armor. This would result in a dead zone of failure out to the range that corresponds to that velocity.
armor plate (30 ° inclination
tion):


7.5 cm V. 100 500 1000 1500 2000


KWK 37

rot.Pz 365 M/s, 41 39 35 33 30 (mm)


7.5 cm Kan L40

rotPz. 685M/s, 65 64 62 59 56

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Re: Allied tank armor, quality control

Post by Mobius » 15 Apr 2019 22:14

I was thinking that the Russians may have had these projectiles if they existed. Then they might have tested them.
In this chart the gun of the T-4 tank.
viewtopic.php?f=47&t=215918&p=1948055&h ... e#p1949213

It seems the KwK 40 gun doesn't conform to K=2400 of the Russian ARTKOM DeMarre formula. The table values are below a calculated penetration from ARTKOM formula of a Pzgr 39 shell. Now this may be because the Russians didn't model the ballistics correctly.

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Re: Allied tank armor, quality control

Post by Yoozername » 16 Apr 2019 13:58

@Mobius....You think the K. Gr.rot.Pz would perform at 770 M/s? That Soviet document has many issues.

In any case, this is the earliest KWK 40 document I have that shows the Pzgr 39 round. Note the Tag Monat Jahr dates. Note that it is the two part penetrator (welded). Also note it is the early 'Ladung' (propellant) of 2.43 Kg. Later versions of this ammunition increased this to 2.5 Kg.

This would be the ammunition used in the initial Panzer IV F2 slowly coming off the production lines in 1942. Also, it would be used in the initial StuG III F versions with the L43 barrel.

The actual barrels for the Pak 40 and panzer IV F2/G (L43) and StuG III F were basically the same. The L46 of the Pak 40 is somewhat misleading, since it is a measurement of the length from the end of the barrel, to the back of the sliding block. The difference in L43 and L46, that is '3', is just the difference in the length of the 'brass' or Patronenhulse. Basically, from a physics standpoint, the actual rifling distance, that is the 'pressure vessel', is the same for each of these weapons. Also, the twist, at this time, was also the same; It was a progressive twist. The major difference is the actual Ladung of propellant. The KWK 40 and StuK 40 shared the same ammunition, and therefore, the same velocity. Most documents put the velocity at a nominal 740 M/s.

The picture shows a collector has put images of his cut out display. It has a 1/4 sector cut out and it is museum quality work. It probably is the later one part penetrator.

I believe this dispels any notion that the KWK 40 and StuK 40 were not initially designed to fire Pzgr 39. If there is any evidence that they were forced to use K. Gr.rot.Pz in some 'substitute standard' fashion, or depot level modifications, etc., I would like to see it. Again, the velocity of the guns would make shooting at the very critical close to medium ranges beyond the performance of the weapon, and given the actual threats (T34 and KV), it would have been inadequate.
1942pzgr39.jpg
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Re: Allied tank armor, quality control

Post by Mobius » 16 Apr 2019 15:37

Yoozername wrote:
16 Apr 2019 13:58
@Mobius....You think the K. Gr.rot.Pz would perform at 770 M/s? That Soviet document has many issues.
I don't know.
You know that the German penetration criteria was for the shell charge to remain in burst condition while the Soviet involved only a percentage of the mass to pass through the armor. So a Soviet graph of penetration of the K. Gr.rot.Pz would be different than the German.
At MV=770 m/s a 75mm shell would be at 758 m/s at 100m.

That Russian table sometimes mirrors actual penetration and sometimes not.

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Re: Allied tank armor, quality control

Post by Yoozername » 16 Apr 2019 15:44

There is some data of the US firing them at Aberdeen at higher velocities. I will have to dig it up. Also, compare it to German and Soviet tests regarding effectiveness of Pzgr 39 vs. T34. One could basically find the 'dead zone' of firing K. Gr.rot.Pz against T34. It might be useless against the glacis. At all ranges.

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Re: Allied tank armor, quality control

Post by Peasant » 16 Apr 2019 22:42

Mobius wrote:
16 Apr 2019 15:37
Yoozername wrote:
16 Apr 2019 13:58
@Mobius....You think the K. Gr.rot.Pz would perform at 770 M/s? That Soviet document has many issues.
I don't know.
You know that the German penetration criteria was for the shell charge to remain in burst condition while the Soviet involved only a percentage of the mass to pass through the armor. So a Soviet graph of penetration of the K. Gr.rot.Pz would be different than the German.
At MV=770 m/s a 75mm shell would be at 758 m/s at 100m.

That Russian table sometimes mirrors actual penetration and sometimes not.
The reverse ARTKOM formula with W=6,8kg; D=0,75dm; T=1,03dm and V = 770m/s returns K=2402, so it's safe to say it was calculated.
Extracting the velocities with assumption that K=2400, results in this:

Image

Clearly they have made some erraneous assumptions about PzGr.39 external ballistics.

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Re: Allied tank armor, quality control

Post by Mobius » 17 Apr 2019 01:54

Peasant, are you mixing MV=770 m/s gun shells with MV=790 m/s shells? My reverse ARTKOM gives 600.8 m/s @ 1000m for 74mm.

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Re: Allied tank armor, quality control

Post by Peasant » 17 Apr 2019 10:17

Mobius wrote:
17 Apr 2019 01:54
Peasant, are you mixing MV=770 m/s gun shells with MV=790 m/s shells? My reverse ARTKOM gives 600.8 m/s @ 1000m for 74mm.
I'm starting to think there were no "770m/s" shells at all. Because the reverse ARTKOM formula gives the velocity for 100m point as 770(769 actually) m/s and plotting a curve through all the points intercepts the velocity axis at 790m/s.

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Re: Allied tank armor, quality control

Post by Mobius » 17 Apr 2019 17:21

Peasant wrote:
17 Apr 2019 10:17
Mobius wrote:
17 Apr 2019 01:54
Peasant, are you mixing MV=770 m/s gun shells with MV=790 m/s shells? My reverse ARTKOM gives 600.8 m/s @ 1000m for 74mm.
I'm starting to think there were no "770m/s" shells at all. Because the reverse ARTKOM formula gives the velocity for 100m point as 770(769 actually) m/s and plotting a curve through all the points intercepts the velocity axis at 790m/s.
I've checked this two different ways and I get 100m=757.2 m/s. Have you checked your algorithm against other Russian tables?

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