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

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
Post Reply
Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#91

Post by Yoozername » 07 Apr 2017, 03:40

You have a link? I believe you did say that you were putting 750 M/s in Panzer Command...for Pak 40?

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#92

Post by Yoozername » 07 Apr 2017, 03:43

This is a Pak 40 powder bag from late in the war...2.730 kg
assembled October 25th, 1944
pak40bag.jpg
pak40bag.jpg (33.27 KiB) Viewed 1156 times


User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

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

#93

Post by Mobius » 07 Apr 2017, 13:55

Yoozername wrote:You have a link? I believe you did say that you were putting 750 M/s in Panzer Command...for Pak 40?
I don't have it. Probably was something OT so is hard to locate.
Not just Pak40 I want to have evolving ammo of all kinds.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#94

Post by Yoozername » 07 Apr 2017, 20:13

Hopefully, someone will come in with more information.

I would say that given the evidence, the KWK 40/StuK 40 story was an early Pzgr round of 2.43 Kg that was standardized to a maximum of 2.5 Kg through the rest of the war. The muzzle velocities for, the L43 and L48 being 740 M/s and 750 M/s for the first round, and 750 M/s and 770 M/s for the standard round.

The Pak 40 may be 2.75 Kg initially, perhaps dropped to 2.69 during 1943, but clearly was brought back up in 1944 to 2.73. Velocities being 792 M/s initially, dropped to 770 M/s in the mid-term, and then back to 790 M/s in the late war. Hopefully some documentation regarding the mid-term comes up.

If anyone wants a link to the April 1944 powder weight PDF, let me know.

I am always curious why the 7,5 cm Pak 39 (Hetzer and jagdpanzer IV) are not in these documents? It also uses the same ammo as the KWK 40/StuK 40. It must have a better recoil system also since it does not need a muzzle brake.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#95

Post by Yoozername » 07 Apr 2017, 20:52

Here's a Pak 40 silk bag for possibly a HEAT or smoke round...they used some old powder for this one..

http://relicsww2.com/index.php?route=pr ... 49&page=29

Miles Krogfus
Member
Posts: 474
Joined: 08 May 2015, 20:54
Location: San Diego, CA

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

#96

Post by Miles Krogfus » 07 Apr 2017, 22:53

Two of the producers of the 7.5 cm gun barrel were Hoesch AG of Dortmund and Rhurstahl Heinrichschutte Werke of Hattingen. They used the best type of furnaces and had excellent quality control. Thus their barrels were superior in length of round firing life, muzzle velocity and APBC accuracy down range.
The Krupp 4 AKB 9524 graph shows these differences in 7.5 cm Pzgr 39 perforation of armor plate in velocity: 70 mm of plate pen. by best AP at 575 m/s, mass produced at 605 m/s, 100 mm pen. 745 and 780 m/s, 150 mm pen. 952 and 998 m/s. Average = circa 5% difference. As regards mm pen. at the same velocity: when 70 mm is penetrated by best AP, mass produced pen. 63 mm, with 100 mm pen. by best, 94 pen. by mass, at 150 mm pen. by best, then 137 mm pen. by mass produced.
As the two hardness samples of 7.5 Pak 40 APCBC I posted drawings of above, the actual penetration of tank armor performance at different ranges of any gun must consider various quality factors. Velocity and accuracy figures in any German firing table were approximate, given to help, not to overly control the behavior of Panzer and Pak crews.
Last edited by Miles Krogfus on 08 Apr 2017, 20:12, edited 3 times in total.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#97

Post by Yoozername » 08 Apr 2017, 00:54

The Germans had acceptance tests for almost everything. Including armor plate, projectiles, complete weapon systems, etc. So, while there is always a spread in anything produced, the Germans were looking for specific quality results. It is certainly possible that there were 'good-enoughs' and better.

Typically, troops were given information on the ranges to best engage and to keep away from the enemy. A StuG SOP might be to engage enemy T34s at 800-1200 meters, and to not let them get within 600 meters. And the ability to gauge range, without a range-finder, varies with the troops also!

I think we discussed the German AP projectiles before.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#98

Post by Yoozername » 08 Apr 2017, 21:46

D 435-1 - Handbuch - Die Munition der deutschen

The Pak 40 data in the above document, dated April 1943 shows 2.75 Kg propellant. Interestingly enough, the KWK 40/StuK 40 is still 2.43 Kg. I would theorize that until they got the L48 version for the Panzer IV in Spring 43, they kept the lower 2.43 Kg. So, perhaps by Kursk, thy would have the 2.5 Kg versions.

User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

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

#99

Post by Mobius » 12 Apr 2017, 19:07

Miles Krogfus wrote:Schusstafel H.Dv. 119/324 was first issued in August 1942, a revised version appeared October 1943, and was reprinted October 1944. Supplements were also issued. Below are three excerpts from the Oct 43/44 edition. Note that after the L/43 gun was discontinued, the Pak 40 L/46 got the same barrel rifling as the L/48.
I already have posted above the change in the Pak 40 APBC propellant 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. Remember that the L/48 APCBC propellant amount was raised.
As more secondary companies got involved in 7.5 cm Pzgr 39 production, reports show up to a 10% difference for some APCBC in nose hardness for the Pak 40 (and a 12% difference for the Panther's Pzgr 39/42) which affected their performance.
Is there a Firing Table for the 770 m/s gun? Primarily I'm looking for m/s at ranges.

Miles Krogfus
Member
Posts: 474
Joined: 08 May 2015, 20:54
Location: San Diego, CA

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

#100

Post by Miles Krogfus » 12 Apr 2017, 20:05

I post here a page from the report on Pak 40 APCBC FMAM-289. A hardness drawing of it I posted above. Note #16. Beiladung ignites the propellant, it does not add to its velocity.
Attachments
beiladung 001.jpg

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#101

Post by Yoozername » 12 Apr 2017, 20:38

That would be the Pak 40 Fur Tropen you mentioned before. 2.61 Kg is 5% less than 2,75 Kg. Assuming a linear relationship, IF it were fired in a 'non-tropical' environment, the velocity might be around 750 M/s. But, I am thinking that it might be a non-linear relationship, but for small changes in weight, it is a good approximation.

One could compare the KWK 40 L43 and Pak 40 since, as said before, the actual length of rifling (travel under pressure) is the same. Rifling was initially the same also. One could certainly say that IF the pak 40 was possibly 750 M/s (at normal temps), THEN it would have to have a similar charge as the KWK 4O, which it never did.

Basically, {2.5/2.75} x 792 M/s= 723 M/s. Since the velocity should be 740-750 M/s or so, one could use curve fitting and a second order equation.

It may be SQRT(2.5/2.75)*792=755...this would be KWK 40 L43 firing later rounds

SQRT (2.43/2.75) *792=744...this would be the earlier KWK round

The L48 is longer and can not be compared like this. It can be compared to the L43 in that it was longer by 5 lange. The length does not add much velocity. It is primarily the amount of powder that achieves velocity. The longer barrel may have helped with accuracy.

Edit: "Note #16. Beiladung ignites the propellant, it does not add to its velocity."
It is actually a fine grain propellant? How does it not add to the velocity? It is small but it it isn't a spark plug? Look at it's chemical composition.

Miles Krogfus
Member
Posts: 474
Joined: 08 May 2015, 20:54
Location: San Diego, CA

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

#102

Post by Miles Krogfus » 13 Apr 2017, 21:06

Beiladung is not propellant. It is igniter. It causes the propellant to come into action . . . Thus the Germans did not include its weight directly with the listed 2.61 kg weight given above of the actual propellant that caused muzzle velocity along with: ambient temperature and that of the propellant, gun barrel temperature and its wear depending on its round life and initial quality, the qualities of its container and the AP itself, such as rounds that are slightly unbalanced . . . I have many German studies/test firings, lists and charts that reveal such things. Also note that figures of the expected armor plate penetration for mass produced 7.5 cm APCBC fired by German artillery and Panzer guns are not given in the data sheets war gamers continue to follow. I include these figures above.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#103

Post by Yoozername » 13 Apr 2017, 23:39

I arranged your data so it is readable...please let me know if it is what you are saying?
The Krupp 4 AKB 9524 graph shows these differences in 7.5 cm Pzgr 39 perforation of armor plate in velocity:
70 mm of plate pen. by best AP at 575 m/s, mass produced at 605 m/s,
100 mm pen. best AP at 745 and mass produced at 780 m/s,
150 mm pen. best AP at 952 and mass produced at 998 m/s.
Average = circa 5% difference.
As regards mm pen. at the same velocity: when 70 mm is penetrated by best AP, mass produced pen. 63 mm, with 100 mm pen. by best, 94 pen. by mass, at 150 mm pen. by best, then 137 mm pen. by mass produced.
Can you post the chart? Also the method? It would be interesting. I assume it is 60 degrees, homogenous? hardness? Thicker plates are generally softer, which makes me doubt this data. Specifically, if hardness was an issue, then a better projectile would outperform. But as the plate became thicker and softer, the difference would not stay the same. This is a Krupp test? Of Krupp vs.competitor's products?

The 5% difference is in velocity? The actual kinetic energy is 10-11% difference. I would assume that actual testing was done on plates 70mm, 100mm and 150mm thick. That is, they varied the charge and used something like a Panther gun as a test bed. This is typical testing method of the Germans. The last data is extrapolated and shows a KE relationship. the Germans did not make 63mm, 94mm and 137mm test plate...

Miles Krogfus
Member
Posts: 474
Joined: 08 May 2015, 20:54
Location: San Diego, CA

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

#104

Post by Miles Krogfus » 17 Apr 2017, 20:12

Wa Pruf (Ballistics and Munitions) 1 at Hillersleben worked with makers of armor plate and AP, studying how changes in the muzzle velocity of guns affected (1) their range (2) their accuracy (3) their armor plate penetration (4) their barrel life. Such testing on one type of barrel could last 6 months or more. One example: I give length of tube/propellant weight/muzzle velocity/life of tube figures for a new design of a 5.5 cm barrel tube design of Rheinmetall-Borsig A.G:
2500 mm/.57 kg/800 meters per second/5500 rounds.
4200/1/1000/1500.
6800/1.83/1200/500.
11150/3.25/1400/150.
6/9 rifling on the 7.5 cm barrel initially gave it better MV and accuracy than the 7 rifling barrel, but reduced tube life, causing the 6/9 tube to be discontinued. Hillersleben created and revised the 7.5 cm KwK/Pak/StuK FT, and with the help especially of R-B, adjusted propellant weight and other barrel/APCBC round elements to settle at circa 750 m/s muzzle velocity for the Pzgr.39 of all Kwk/Pak/StuK gun versions that were continued in production and grouped together in H.Dv.119/324.
With countless pages of German firing tests and TL graphs relating to AP and Panzer plate quality, I will quote and post some of these when I display and discuss pages from the Panther FT, Tiger I and II FT and . . . However I next will turn to more posting on Operation Citadel Panzer unit "shoot out" performances.
Last edited by Miles Krogfus on 18 Apr 2017, 01:39, edited 2 times in total.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

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

#105

Post by Yoozername » 17 Apr 2017, 22:15

6/9 rifling on the 7.5 cm barrel initially gave it better MV and accuracy than the 7 rifling barrel, but reduced tube life, causing the 6/9 tube to be discontinued. Hillersleben created and revised the 7.5 cm KwK/Pak/StuK FT, and with the help especially of R-B, adjusted propellant weight and other barrel/APCBC round elements to settle at circa 750 m/s muzzle velocity for the Pzgr.39 of all Kwk/Pak/StuK gun versions that were continued in production and grouped together in H.Dv.119/324.
If you have a source for this, it would be great. I am especially wondering what "other barrel/APCBC round elements" actually means? Unless you are just interjecting that? And, just to be clear, are you speaking of the Pak 40 or the KWK 40 L43?

So, when exactly did this happen? The Pak 40 had a full charge till April 1943. The L48 KWK 40 StuKs were around in the Fall 42(7 deg), KWK 40 L48 came online later, Spring 1943.

I know the initial L48 actually had the progressive rifling, and it was discontinued quickly (from the StuKs), and then StuK 40 then had uniform twist rifling on the L48s in 1942. I do not know if that is what you are referring to?

If I follow you, you are saying that the KWK 40/StuK 40 L48 version, firing 2.5 Kg charges fired at 750 M/s? And the Pak 40 firing a 2.71 Kg charge also had a muzzle velocity of 750 M/s? With the later 7 degree rifling in each, the big difference would be the 5 lange difference in the L48?

BTW, The PAK40 rifling is progressive from 1/24 to 1/18, which is what the '6/9' refers to. Basically it starts at a slower rate and increases. One turn in 24 calibers then to one turn in 18 calibers.

Image

Post Reply

Return to “The Ron Klages Panzer & other vehicles Section”