German 75mmL43, L48 and L46 velocities

[Elron Hubbub]

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[Mobius]

ORIGINAL: Elron Hubbub
I am afraid that you have things backwards. It is you that is claiming that it was changed. But you want someone that does not believe it was changed, to prove it? I would even be willing to see a second hand source at this point.
Do you have the full report from Aberdeen?

I have a datenblatt that says its 750m/s;
tm.asp?m=2691742#3213842
And then I have a book that quotes Aberdeen that says its 790m/s as well as the firing test.
790<>750 so there is a change.

[Elron Hubbub]

That is a 'form' that has been filled out. It isn't even dated? That... is it? It looks like some quote or invoice.

So, if you think it was 750 M/s, then what powder charge does that correspond to?

[Elron Hubbub]

But, I am interested in the 1944 data. We have this data in the 7/42 PaK 40 pdf from the old German doc site.

Yes, it shows that 6 months later, the Pz Gr 39 ammunition has the same powder weight. But it also shows that the PzGr 40 is listed as 2.7 Kg, which is higher than the 7/42 value.

If there were real issues with the ammunition, do you really think that it would not be addressed in this supposed powder reduction you theorize when it was first fielded?

To be honest, I am not sure what your position is now.

[Mobius]

ORIGINAL: Elron Hubbub
That is a 'form' that has been filled out. It isn't even dated? That... is it? It looks like some quote or invoice.

It's probably from a test results. It has the Hl/C round so it has to be after it was introduced. And not printing it up in old Gutenberg German doesn't make it less authentic.

ORIGINAL: Elron Hubbub
So, if you think it was 750 M/s, then what powder charge does that correspond to?

Well the KwK 40 had around 2.50 kg so unless the type of power changed it should be around that.

[Elron Hubbub]

Probably? You don't know the document it came from do you? Do you care? I can tell you.

[Mobius]

ORIGINAL: Elron Hubbub

Probably? You don't know the document it came from do you? Do you care? I can tell you.

I don't care what the charge is. I care what the muzzle velocity is. How it gets there is not my concern.

[Elron Hubbub]

Yes, that document doesn't show the charge either. It shows the price.

[Elron Hubbub]

CAMD RF 81-12038-303

This shows the Pak 40 is 770 M/s or do they mean "T-4" as in KWK 40?

[Mobius]

ORIGINAL: Elron Hubbub
CAMD RF 81-12038-303
This shows the Pak 40 is 770 M/s or do they mean "T-4" as in KWK 40?

CAMD RF 81-12038-303
http://tankarchives.blogspot.com/2013/0 ... ation.html

I think they mean the Mark IV's gun. But there are a few things wrong with that chart. In particular:
http://tankarchives.blogspot.com/2014/0 ... links.html
How can the 770m/s 75mm penetrate only 74mm at 1000m and then penetrate the front of a T-34 at 1000m?
AA has some very interesting things but they are not all consistent. And the site owner comes to some real incorrect conclusions which I point out on occasion.

Also, the wiki mentions that in an October 1943 German Pak 40 document does at one point lists the muzzle velocity at 770 m/s. (It might even be a misprint as I found one in the 88mm/L71 firing table.) This document could of fell into allied hands and is the source of all the 770m/s information.

[Elron Hubbub]

What is your source of the supposed cartridge problems with the PAK 40? Date?

[Mobius]

Spielbergers Sturmgeschutz book page 64:
"On 14 April 1942 results were reported for the test firing which had taken place in Hillersleben on April 3rd. The first gun tested (R V 1), installed in a Sturmgeschutz, had experienced twice failed to eject spent shell cases out of 87 rounds fired, utilizing shelsl that had been warmed 10 to 35 degrees centigrade. "

[Elron Hubbub]

PAK 40?

[Elron Hubbub]

I think this graphic shows the transition in 1942 of German AFV production. Mid-year shows that light tanks have ceased production. April 1942 shows the change-over of both Panzer IV and StuG to KWK 40 L43 weapon. The StuK 40 is changed to a L48 version while the Panzer IV stays the L43 (till early 1943).

Both Panzer IV and StuG III share the same ammunition cartridges. Ammunition production has reached operational levels, and in Nov 1, 1942, it has reached comparable levels to Panzer III ammunition stocks even though the Panzer III had already achieved high production and fleet levels.

7,5 cm weapon issues at this time were the changeover from progressive rifling to constant rifling in the L48 barrel, and design changes for the muzzle brake. Field reports certainly claim success as far as the ability to destroy enemy armor.

[Mobius]

ORIGINAL: Elron Hubbub
PAK 40?

This is what I wrote:

3. The 75mm/L46 Pak 40 having a different style cartridge kept its muzzle velocity at the design 790 m/s for a longer period of time. Though later in the war, for some reason, maybe training or consistency, the charge was reduced and the muzzle velocity became 750 m/s as well

[Elron Hubbub]

ORIGINAL: Mobius

ORIGINAL: Elron Hubbub
PAK 40?

This is what I wrote:

3. The 75mm/L46 Pak 40 having a different style cartridge kept its muzzle velocity at the design 790 m/s for a longer period of time. Though later in the war, for some reason, maybe training or consistency, the charge was reduced and the muzzle velocity became 750 m/s as well

And your only source is a hand filled in form? And you do not have a date?

The amazing part is the ramp up in ammunition production in 1943. In other words, if they had the hundreds of thousands of rounds for the PAK 40 in Nov, 1 1942, and the actual number of PAK 40 pieces were just coming into units, you think they would really reduce the charge and change the ammunition stocks? They would decrease the performance for "training or consistancy"? Basically, this means every PAK 40 cartridge would be partially filled.

I guess the testing done by the US (776 M/s?) used a mix of cartridges that would have been marked with different powder weights and no one at the Aberdeen facility might notice?

[Elron Hubbub]

Oh! Look! Panther side armor is 40mm! For all versions. Guy that filled in this form says so...

[Mobius]

ORIGINAL: Elron Hubbub

ORIGINAL: Mobius

ORIGINAL: Elron Hubbub
PAK 40?

This is what I wrote:

3. The 75mm/L46 Pak 40 having a different style cartridge kept its muzzle velocity at the design 790 m/s for a longer period of time. Though later in the war, for some reason, maybe training or consistency, the charge was reduced and the muzzle velocity became 750 m/s as well

And your only source is a hand filled in form? And you do not have a date?

Actually, that's where the trail ended. It started on a World of Tanks blog interview with tank expert Hillery Doyle. (Who did drawings for Jentz and Spielberger.)
He said the Pak 40 had a MV of 750. I didn't believe it so to prove him wrong I started looking at his reference. That was a US 1955 manual
https://archive.org/details/Dapam30-4-4
(the pdf was/is free online)
That said the US reprinted German data and didn't acquire the data through testing. Somehow I used it to find the datenblatt site.
Note the reason the Pak 40 is in the document.

This piece is still in service or held in reserve in Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, and Rumania.

The daten sheets on the guns are all made out by hand.

[Elron Hubbub]

As far as the theory "training or consistency"...The PAK 40, KWK40 and StuK 40 all used different sights?

Speaking of training...they would then have to change the Ub rounds also?

[Elron Hubbub]

Those "data sheets" can be construed to be second hand , BTW.

The document they are from (Stoffgliederung 21 Heeresdienstvorschrift) was collated in 1944 at the behest of Reichminister für Rüstung und Kriegsproduktion (RfRuK). I have seen other pages and they are apparently all filled in 'standardized' forms that one person (same hand writing) is transferring information into. The person, of course, is not a test engineer but some clerk. The KWK 40 is not filled out completely BTW. There are other issues pointed out on grog type websites.

The intent seems to centralize weapons information from all branches. Other websites state that armor penetration and abbreviations are wrong. The person filling those out would not know a L48 from his shwanz.