7,5 cm Kwk/StuK/Pak 40 Firing Table Data

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Yoozername
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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 18:16

This is from December 1942...the extremely rare (especially for the Pak 40) Pzgr 40 shows the higher powderweight...

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 19:01

The Germans printed much information on the actual ammunition. In some cases, it should be taken as the nominal value. The propellant was stuffed into the 'brass' in a bag. On the bag is printed the actual measured weights and dates...here is an example of a KWK 40/StuK 40 bag...the dates were for the propellant manufacture, and also when the ammunition was assembled...in this case the 27th week of 1943, and assembly being June 23, 1944. Powder had a shelf life of one year and so did assembled ammunition...

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Miles Krogfus » 06 Apr 2017 19:07

Here are illustrations of the two versions of the Pak 40 Pzgr 39. FMAM-289 was produced in October 1942 and is the two piece welded version with excellent nose hardness of an average 733 VDH. The figure 3 illustration shows the one piece version produced in November 1942 with a lower average nose hardness of 656 VDH and thus less penetration ability.
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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 19:21

This would be the nominal values for a KWK 40/StuK 40 pzgr 39...

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 19:46

To be absolutely clear, Miles Krogfus posted this data...
A 1942 welded small HE cavity 75 mm APCBC for the Pak 40 examined in the United States had a projectile weight of 14.65 lb (6.645 kg) and a propellant charge of 2.610 kg bagged on October 7,1942. Marked "Fur Tropen P.T.+ 25 (degrees) C."

Page 12 for 7.5 cm Pzgr Patr 39 Pak 40: etwa 2.690 kg Digl RP--G1--(625* 3.8/1.3) + 20 g Nz Man NP ( 1.5/1.5).
And then posted...
I already have posted above the change in the Pak 40 APBC propellant (the amount of propellant for the hard core round also was lowered) resulting in a change of the official muzzle velocities for all the 7.5 cm guns from the 1942 Pzgr 39 770 to the 1943/44 750 m/s and the PzGr 40 from 990 to 930 m/s.
Now, as has been discussed, 'Fur Tropen' is a specific ammunition type used in hotter climates, more than likely captured in North Africa. The propellant weight is reduced to reflect that similar velocities can be attained in hot environments that would be attained in a moderate environment with a full charge . It was not a 'normal' round.

The 'reduced charge' 2.69 should include the 20 gram Nz Man NP making the total weight 2.71 Kg. This is the weight for late 1942? I want to be clear on this since you said that the Pak 40 propellant weight was reduced somehow over the war? Thanks

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Miles Krogfus » 06 Apr 2017 20:08

The 1942 official Pak 40 7.5 cm Pzgr 39 propellant weight was etwa 2.75 kg changed to etwa 2.69 kg while the KwK 40 Pzgr 39 propellant weight was 2.43 kg changed to 2.5 kg. Their added Beiladung I do not include. PzGr 40 was not lowered in propellant. However different elements of a propellant produce varied results, thus when either types of material or their % in a propellant are changed, mv also can be modified.

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 20:23

So, the H. Dv. 481/58 Merkblatt from July 6, 1942? and the velocity most quote at that time is 790-792 M/sec? Correct?

https://www.scribd.com/document/1425946 ... 06-07-1942

When was it changed to 2.69 Kg? Or what document was that? It seemed to still be 2.75 Kg in Dez 1942? see my post above...

Edit: this was actually published in April 1943...

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Miles Krogfus » 06 Apr 2017 21:04

Having studied German AP, Panzer plate and RAL paint, I have noticed that factories received by mail new regulations, orders and notices 2 to 3 weeks after the issued dates. For paint, a factory was allowed to use up, for example, the previous primer color before using the new color. Completed Panzer plate, AP and their bagged propellants were stored at their original makers for weeks to months before being completed there or shipped for completion elsewhere. The October 1943 FT lists Pzgr 39 2.69 and 2.5 kg. weights and their FT drawings also show these weights. However, the date that this change was ordered could have been earlier. When these changed propellant weight rounds were shipped to combat units in 1943 is open to question . . .

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 21:20

As a side note, regarding the KWK 40/StuK 40...I corresponded with the author of the StuG books....He said....(I would assume it is the later 2.5 Kg Pzgr 39)
Well, the difference was'nt that big. In my StuG-Book (coming in English this Year (probably by RZM Imports) I've included a test table of the Armament Office.
Test 8.4.44:

L/43: Vo 750 m/s, the Pz.Gr.39 penetrated (1000m 60°) 81 mm
L/48: Vo 770 m/s, the Pz.Gr.39 penetrated (1000m 60°) 84 mm

The tests were performed several times during the war

Peter
from http://www.historyfacts.biz/en/

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 21:22

I will wait till Mobius has anything to say...we have discussed this for years...

But IF it is 2.69 Kg for the Pak 40, THEN assuming a linear relationship between powder weight and velocity, this would NOT give 750 M/sec for the Pak 40. It would be something like 774 M/sec...but Mobius has some dealings with me regarding this...and he should suspect I have something up my sleeve....

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 06 Apr 2017 22:36

There are plenty of people that actually believe that the Pak 40 muzzle velocity was reduced to 750 M/s, and second hand documentation from the Allies seem to propagate this. Given the data that Miles provided, it is simply a matter of stating the following logic to dispell this....

IF the Pak 40 and KWK 40 L43 had the same projectile (true), AND the same rifled distance that the projectile is under pressure (also true), THEN the muzzle velocities would be the same ONLY IF the propellant charge is the same!

Clearly, the Pak 40 never reduced its charge to 2.41 Kg or 2.5 Kg.

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Mobius » 07 Apr 2017 00:53

Denniss wrote:"60m über dem Meere" = 60m above sea level
Thanks. I had assumed it was the elevation of Kummersdorf which would be about 40m above sea level.

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Denniss » 07 Apr 2017 01:24

Mobius wrote:
Denniss wrote:"60m über dem Meere" = 60m above sea level
Thanks. I had assumed it was the elevation of Kummersdorf which would be about 40m above sea level.
The firing table was generated at the shooting range Hillersleben. Further specified is air weight of 1.22kg/cm³, still air and powder temperature of +10 degrees Celsius

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 07 Apr 2017 02:12

Denniss wrote:
Mobius wrote:
Denniss wrote:"60m über dem Meere" = 60m above sea level
Thanks. I had assumed it was the elevation of Kummersdorf which would be about 40m above sea level.
The firing table was generated at the shooting range Hillersleben. Further specified is air weight of 1.22kg/cm³, still air and powder temperature of +10 degrees Celsius
I don't see a firing table, aside from the recoil distances, there is no actual velocities listed. I think Miles cut and paste parts together from the actual report?

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Re: 7,5 cm Kwk/StuK/Pak 40 Firing Table Data

Post by Mobius » 07 Apr 2017 02:34

Yoozername wrote:Clearly, the Pak 40 never reduced its charge to 2.41 Kg or 2.5 Kg.
I think I already posted about this. That someone on another forum was saying that the charges were slight different chemically. As to cause the wider shorter KWK cartridge to take as much time to burn as the slimmer longer PaK cartridge. I don't know if that is true or not.

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