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

[peeved]

I have no idea where he gets 10% though.

I'd imagine 30 x 0,3% [of the FT MV]= 9% ≈ 10% in keeping with the MV approximations.

Ooops...should be 30 x 1/3% = 10% since each step down from new barrel MV was one third of a percent.

And if firing table MV is 750 m/s then
MV from a new barrel would be 1,03 x 750 m/s = 772,5 m/s ≈ 770 m/s and
MV from a worn-out barrel ca. 770 m/s / 1,10 = 700 m/s
Conversely if
MV from a new barrel was 790 m/s then
FT MV should be ca. 790 m/s / 1,03 = 767 m/s ≈ 770 m/s
MV from a worn-out barrel ca. 790 m/s / 1,10 = 718,2 m/s ≈ 720 m/s

Technically the calculations are still somewhat off since the first 10 steps down are just 3% instead of 3,33333333.... but adequate for approximation.

Markus

[peeved]

Interesting theory. But why are the only known German Firing Tables are at the Vo = 750 m/s level?

Maybe because Bundesarchiv hasn't digitised e.g. H.Dv. 119/324 Vorläufige Schußtafel für die 7,5 cm Kampfwagenkanone 40 (7,5 cm Kw. K. 40) und 7,5 cm Sturmkanone 40 (7,5 cm Stu. K. 40) from August 1942; I've only seen excerpts from the 1944 edition.

Markus

[Mobius]

post removed

[Yoozername]

Interesting theory. But why are the only known German Firing Tables are at the Vo = 750 m/s level?

Maybe because Bundesarchiv hasn't digitised e.g. H.Dv. 119/324 Vorläufige Schußtafel für die 7,5 cm Kampfwagenkanone 40 (7,5 cm Kw. K. 40) und 7,5 cm Sturmkanone 40 (7,5 cm Stu. K. 40) from August 1942; I've only seen excerpts from the 1944 edition.

Markus

Here is the 1943 version but it does not have the FT.

http://michaelhiske.de/Wehrmacht/Heer/H ... bl.htm#top

It is interesting that the KWK 40/StuK 40 are only included in the 1942 version.

[Denniss]

The sources that specified 770m/s also used a powder temperature specified at +10°C ?

[Yoozername]

There appears to be some conflicting information regarding the Tungsten (Pzgr 40) ammunition in the 1944 version H.Dv. 119/324. The document claim a MV of 930 M/s for all the 7,5 cm weapons, yet the powder weights clearly show that the Pak 40 has a much higher charge. That is KWK 40/StuK 40 has 2.1 Kg or 2.18 Kg, while the Pak 40 has 2.60 Kg or 2.70 Kg depending on the powder type (same powder types for each ammunition). There is no way that they could have the same velocity. The powder types are not the same as Pzgr 39 (Digl.), BTW. That is, they are the powder types used in HE/HEAT/smoke.

At this stage of the war, Pak 40 Pzgr 40 may have been completely none existent and some old data just used. Also, MB 28-1 April 1944, pak 40 shows 2.37 Kg and using the same powder as regular Pzgr 39 (Digl.). The Dez 1942 data for the Pak 40 shows 2.7 Kg and using the Digl. powder.

Clearly, the Pzgr 40 for the Pak 40 was rare. Even rarer than the KWK 40/StuK 40. But it seems odd that there could be 3-4 versions of it used. Initially, given the large powder weight, it would have a very high velocity(990 M/s?). The 930 M/s would seem consistent with a 2.37 Kg Digl. powder weight then. I am using the 930 M/s*SQRT (2.7/2.35)=~990 M/s.

I have some sources that claim that powder weight and velocity are a square function. That is, if you want a projectile to go twice as fast, then quadruple the powder weight. Also, the velocity/pressure and motion profiles are interesting. That is, what velocity is actually attained in the lest few 'lange' of the barrel. It may surprise people.

[Yoozername]

http://www.lonesentry.com/manuals/88mm- ... ables.html

Here is the firing table for the 88mm. It is listed as 810 m/s. So, given the 3%, a 'new' barrel might be 845 M/s or so?

The 88mm weapons were actually checked for muzzle velocity according to a source. That is, in the field. They had a two part barrel and replacement of the front part was a maintenance item. An interesting thing is that the back part of the barrel was a progressive twist. This was actually a slow starting twist (1/45) and then it increased to (1/30), the second part of the barrel was a uniform 1/30 twist! It matched up to the first and the projectile rode out that way. Somewhat different than what other progressive twists do.

[Mobius]

http://www.lonesentry.com/manuals/88mm- ... ables.html

Here is the firing table for the 88mm. It is listed as 810 m/s. So, given the 3%, a 'new' barrel might be 845 M/s or so?

That is the Flak 88mm. Using large cavity Pzgr. Patr. not Pzgr 39. I have 800 m/s for that shell. But that is going OT.

[peeved]

http://www.lonesentry.com/manuals/88mm- ... ables.html

Here is the firing table for the 88mm. It is listed as 810 m/s. So, given the 3%, a 'new' barrel might be 845 M/s or so?

Let's see:
810 m/s x 1,03 = 834,3 ≈ 830 m/s ; Could be but for the fact that AP shell weight in the American print does not match the German types in D 460/1+ Geschoßringbuch: 9,5 kg 8,8 cm Pzgr. , 10,2 kg 8,8 cm Pzgr. 39 or 9,87 kg Pzgr. 39/43. Even the pound conversion is incorrect: 20,75 lbs ≈ 9,4 kg and not 9,65 kg. I don't know an 8,8 cm AP shell MV in a new barrel anyhow so let's look at the HE shell part instead:

Weight 9,0 kg [OK] ≈ 19,8 lb [OK]; MV 820 m/s [OK].

820 m/s x 1,03 = 844,6 ≈ 840 m/s

According to Datenblätter für Heeres-Waffen-Fahrzeuge-Gerät (1944)

Größte V0 (810-820) 840 m/sek, Schußtafel = 820 m/sek

Thus the figures outside the brackets are a match.

Markus

Edit: incorrectly entered unit adjusted

[peeved]

According to Datenblätter für Heeres-Waffen-Fahrzeuge-Gerät (1944)

Größte V0 (810-820) 840 m/sek, Schußtafel = 820 m/sek

Größte V0; I've seen that before: download/file.php?id=399491&mode=view
If highest MV for L/43 PzGr. 39 was 990 m/s then FT MV should be 790 / 1,03 ≈ 770 m/s

Markus

[peeved]

Interesting theory. But why are the only known German Firing Tables are at the Vo = 750 m/s level?

Maybe because Bundesarchiv hasn't digitised e.g. H.Dv. 119/324 Vorläufige Schußtafel für die 7,5 cm Kampfwagenkanone 40 (7,5 cm Kw. K. 40) und 7,5 cm Sturmkanone 40 (7,5 cm Stu. K. 40) from August 1942; I've only seen excerpts from the 1944 edition.

Markus

Here is the 1943 version but it does not have the FT.

http://michaelhiske.de/Wehrmacht/Heer/H ... bl.htm#top

It is interesting that the KWK 40/StuK 40 are only included in the 1942 version.

Any idea what the H.Dv. number for the 1941...42 Pak 40 FT was? Logically there must have been one since it was introduced into service before KwK/StuK 40.

Markus

[Yoozername]

I have not heard of one. It does seem odd if there isn't one.

Some barrel lives...cut n paste

"Datenblätter" gives the approximate lifespan of barrels for a number of weapons. Example:

Tank guns:
7,5cm KwK 37 = 12-14000 rounds
5cm KwK39 = ~8000 rounds
7,5cm KwK 40 = 5-7000 rounds
7,5cm KwK 42 = ~2000 rounds
8,8cm KwK 36 = ~6000 rounds
8,8cm KwK 43 = ~1200 rounds (Panzergranate 39-1)

Anti-aircraft guns
8,8cm Flak 18/36/37 = 2000-2500 rounds or ~6000 depending on propellant

Anti-tank guns:
3,7cm PaK = 4-5000 rounds
5cm PaK 38 = 4-5000 rounds
7,5cm PaK 40 = ~6000 rounds
7,5cm PaK 41 = ~1000 rounds
8,8cm PaK 43 =~2000 rounds - 1200 with Panzergranate 39-1

[Miles Krogfus]

Above on April 5, 2017 I gave the chronology of the Pak 40 H.Dv.119/324 firing table. It first appeared in August 1942. Also note that when the Pak 40 was used to test Panzer plate quality, the lowest allowed strike velocity (representing 100 meters distance from the plate) was 700 m/s.

[Yoozername]

Above on April 5, 2017 I gave the chronology of the Pak 40 H.Dv.119/324 firing table. It first appeared in August 1942. Also note that when the Pak 40 was used to test Panzer plate quality, the lowest allowed strike velocity (representing 100 meters distance from the plate) was 700 m/s.

But, you did not share it. So...what is the point?

I believe the common theme here is historical research? That is, information not shared is lost...or?

Is it really that big a deal? It would be great if you could share the first August 1942 data since it is a baseline of the first 2.75 kg charge?

Edit: In regards to the 'strike velocity', the Germans used a scheme for the velocity where they changed the powder charge. So, what is your point about the 700 M/s? They are testing the armor...not the gun?

[Yoozername]

D140/159

This seems to be a very early ammunition manual for the Pak 40 rounds. It is noted as 'incomplete' and the lack of Pzgr 40 round is evident. I will post it or get a link for it here.