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

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

Post by Miles Krogfus » 09 Apr 2016 21:40

H.Dv. 119/324 edition dated October 1944:
7.5 cm PzGr 39 of 6.8 Kg and 750 m/s MV with velocities at range and Krupp 4 AKB 9524 30 degree deflection graph performance figures May 2,1944.
100 meters 738 m/s 99 mm pen. 300 meters 715 m/s 95 mm pen. 500 meters 691 m/s 90 mm pen. 1000 meters 637 m/s 80.4 mm pen. 1500 meters 585 m/s 72 mm pen. 2000 meters 536 m/s 63.6 mm pen. 2500 meters 491 m/s 56.3 mm pen. 3000 meters 451 m/s 50 mm pen.
Treffer % firing at 2.5/2 meter target with 50% St. breite/hohe: 100 m 100(100)% .0/.1, 300 m 100(100)% .2/.2, 500 m 100(100)% .2/.3, 1000 m 98(66)% .5/.6, 1500 m 77(33)% .9/1.0, 2000 m 49(16)% 1.3/1.6, 2500 m 28(08)% 1.8/2.4, 3000 m 17(05)% 2.3/3.3.
Note that the penetration of armor plate figures were less for some sub-contractors and non-two piece welded projectiles.

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David W
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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by David W » 10 Apr 2016 06:34

Thanks Miles.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Miles Krogfus » 16 Apr 2016 02:05

7.5 cm Pak 40 sight tube 38 marked for:
Sprgr 34 black # 400 to 2800 meters, Pzgr 39 red # 200 to 1800 meters, Pzgr 40 green # 300 to 1100 meters.
Sight tube 38A marked for:
Spgr 34 black # 200 to 5200 meters, Pzgr 39 red # 200 to 3000 meters, Pzgr 40 green # 300 to 2000 meters, Gr 38 Hl yellow # 200 to 3700 meters.
7.5 cm Stuk 40 sight tube 36 for 37Sf ZF 1a marked:
Spgr 34 black # 400 to 3300 meters, Pzgr 39 red # 200 to 2600 meters, Pzgr 40 green # 300 to 1400 meters.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Miles Krogfus » 21 Aug 2016 19:44

I list British Ordnance Board penetration graphs from 1943 and 1944.
O.B./43/CV.12 May 25,1943 shows for 2400 f/s muzzle velocity (731.52 m/s) of 14.81 lb. APCBC shell ("MV as tested by trial in KwK 40") at 0 and 30 degrees deflection: 2400 f/s penetration 121/102 mm, 2000 f/s (609.6 m/s) 98/83 mm, 1600 f/s (487.68 m/s) 75/63 mm.
O.B./43/CV.13 same date. MV 1350 f/s (411.48 m/s) same shell model: 1300 f/s (396.24 m/s) 58/48.5 mm, 1000 f/s (304.6 m/s) 41.8/34.8 mm.
O.B./43/CV.20 for 15 lb. large HE cavity APCBC 1300 f/s MV December 14,1943: 1300 f/s 50.3/46.25 mm, 1000 f/s 35/32.94 mm.
O.B./44/CV.50 for 15 lb. small HE cavity APCBC December 13,1944 of Kwk 42 MV 3068 f/s (935.13 m/s), Pak 40 MV 2600 f/s (792.48 m/s), KwK 40 MV 2300 f/s (701.04 m/s): 3000 f/s (914.4 m/s) 182/156 mm, 2400 f/s (731.52 m/s) 133/104.5 mm, 2000 f/s (609.6 m/s) 104/77.5 mm, 1600 f/s (487.68 m/s) 75.5/55.5 mm.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 23 Aug 2016 22:34

This is interesting information. There are a few threads that hotly debate the performance of these weapons.

I will forward the British information, it seems there has been a lack of WWII British testing information in this regard. I am glad that there are many non-English speaking people interested in this topic, and much has come to light, but I do not know why more British data isn't on the web. Given the fighting and length of time they engaged the German weaponry, and the detailed studies of Panzers, etc, I would expect them to have fairly intimate knowledge and detailed testing of the guns.

The big issue is that people claim the Pak 40 powder-weight was somehow reduced later in the war to obtain commonality with the KWK weapons (i.e. they all had to have the same muzzle velocity). I see no evidence of this and it seems that it has become 'common-knowledge' and accepted by wargamers and other interested parties. I will forward you a link to a good thread.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 23 Aug 2016 22:49

I cleaned up the data bit...Bold denotes my assumptions

O.B./43/CV.12 May 25,1943 KWK 40 in this test is the L43 version
shows for 2400 f/s muzzle velocity (731.52 m/s) of 14.81 lb. APCBC shell ("MV as tested by trial in KwK 40") at 0 and 30 degrees deflection:
2400 f/s penetration 121/102 mm,
2000 f/s (609.6 m/s) 98/83 mm,
1600 f/s (487.68 m/s) 75/63 mm.

O.B./43/CV.13 same date. KWK 37? Firing a Pzgr 39?
MV 1350 f/s (411.48 m/s) same shell model:
1300 f/s (396.24 m/s) 58/48.5 mm,
1000 f/s (304.6 m/s) 41.8/34.8 mm.

O.B./43/CV.20 for 15 lb. large HE cavity APCBC KWK 37 firing the K.Gr.rot.Pz?
1300 f/s MV December 14,1943:
1300 f/s 50.3/46.25 mm,
1000 f/s 35/32.94 mm.

O.B./44/CV.50 for 15 lb. small HE cavity APCBC December 13,1944 of Kwk 42
MV 3068 f/s (935.13 m/s),
Pak 40 MV 2600 f/s (792.48 m/s),
KwK 40 MV 2300 f/s (701.04 m/s): L43??
3000 f/s (914.4 m/s) 182/156 mm,
2400 f/s (731.52 m/s) 133/104.5 mm,
2000 f/s (609.6 m/s) 104/77.5 mm,
1600 f/s (487.68 m/s) 75.5/55.5 mm.

This last test seems to show all projectiles are common, that is 7,5 cm Pzgr 39 and 7,5 cm Pzgr 39/42 are basically the same. There is German and US data that also reflect this in graphs.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Miles Krogfus » 25 Aug 2016 09:32

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."
The British Ordnance Board OB/43/C.V.11 of May 8,1943 gave these 0 and 30 degree deflection figures (beyond 2500 f/s "unconfirmed by firing" ) for the American 75 mm M61 APCBC, weight 14 lb.5 oz.11 dr. of 2050 and 2650 f/s: 2400 f/s 120/95 mm, 2000 f/s 93/74 mm, 1600 f/s 68/53.5 mm.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 25 Aug 2016 15:00

I have not read of a Pak 40 with a 'Fur Tropen' marking before, thanks. One of the theories regarding the range of muzzle velocities reported for German weapons is that 'Fur Tropen' ammunition, which was encountered and captured in North Africa (maybe Sicily also), would give low readings when tested in other climates. Certainly, Maryland (APG) can be a cool climate at times. Of all the environmental factors, temperature seems to have the greatest effect.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Stiltzkin » 25 Aug 2016 18:13

First of all, every faction conducted these tests differently, this data has to be evaluated accordingly. American tests were normalized to ca.237BHN with partial penetration requirement. Distances must be taken into consideration (up to 1000 yards) and plate sloping (either horizontal or vertical).

For German criteria (penetration and burst):
http://www.panzer-war.com/img33.gif

http://www.panzer-war.com/page43.html
http://www.panzer-war.com/img114.gif
http://www.lonesentry.com/manuals/tme30 ... 4sub6.html

Projectiles are affected by pressure and humidity etc. however the muzzle velocity could never exceed a certain level during WW2 because materials prohibited it (limit), i.e. the materials could not withstand the force (unlike today). USA Naval Ballistic Limit Method

https://de.scribd.com/doc/219173969/WWI ... nd-Gunnery
https://archive.org/details/Dapam30-4-4

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 25 Aug 2016 22:40

That is all true, but as far as muzzle velocity, it is really a matter of internal ballistics, i.e. pressure and humidity are really negligible factors (during these microseconds), and the ability to accurately measure the velocity. And all factions, whether they use M/s or Ft/s, are on the same page.

As a test engineer, I can certainly say that you are measuring at better than 1% accuracy or more. I believe that a magnetized projectile is usually fired between two coils (maybe put a slight distance away so as to not get knocked off by the muzzle blast) that are precisely a known distance apart, and an oscilloscope is used to measure the voltage spikes created by the magnetism passing through the coils. This is certainly within WWII technology means (I should hope).

As in anything (uh oh, a caveat), there is a dispersion of measurement and a MV of 750 M/s is not always attained. It is virtually impossible to get a specification of +/-1 M/s due to many factors.

But I believe the British and US and Germans and maybe the Soviets have the technology to 'speak the same language'. But, things like velocities at range and armor penetration and even what results are needed, are not on the same page. The Germans were very specific about what a penetration was, and the actuation of the HE charge was the real goal. They were perhaps the most stringent and the post-war interviews of them by the British is mandatory reading.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Stiltzkin » 25 Aug 2016 23:21

Pressure and humidity play a role for the trajectory, example: Pakistani, Indian conflict in the mountains, the trajectory is very flat.
For muzzle velocity (I am going to formulate it very simplified) barrel length x propellant.
Well according to BIOS and the Krupp analysis it seems that they were the most stringent (and preferred APHEs) the projectile had to penetrate/burst and not deform or explode in the process, while initial US tests only required 75% to pass in a series of 4 out of 5.
The Soviets usually compensated by using a bigger, "overfilled" HE charge (or preferred capped projs).
As for the tables, they are just visualizations and the speed usually differs, in fact the AP rounds usually failed, in Jentz Panzertruppen it is stated that 33% of all AP shells were usually malfunctioning, during the Spanish Civil War 75% of all Soviet AP shells failed due to bad manufacturing.

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 25 Aug 2016 23:58

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Stiltzkin » 26 Aug 2016 00:35


Yoozername
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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Yoozername » 26 Aug 2016 00:43

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Re: 75 mm Kwk/StuK/Pak 40 Firing Table Data

Post by Stiltzkin » 26 Aug 2016 01:11

No, those issues were present throughout the entire war for all factions to a certain degree, also concerning the Pak 40. In the Pacific almost 50% of all Torpedoes were misfires (but thats a nother story).
With that said , muzzle velocities close to (and over ) 1050, 1100 for WW2 are always dubious, since the ballistic limit would be achieved. Contempory subcaliber rounds calculations also include Bernoullie, modified DeMarres equation.
With that said http://imgur.com/jqVMieq
http://www.dtic.mil/dtic/tr/fulltext/u2/a955285.pdf

The first one seems to be the 43
Most MVs for the 40s are given from 750-770 (the lowest was around 711-721 actually).
The 2nd one looks like a 37.
Actually, these values would indicate that there was no general standardization or the shells haven't been correctly identified. Wouldn't the guiding tapes of the 39/42 have an impact? The steel quality did change though in the 39 versions.
Last edited by Stiltzkin on 26 Aug 2016 01:39, edited 11 times in total.

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