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

[Yoozername]

Outright penetration wouldnt be expected from-40W.
There might even be no holing event. Inside armour scabbing is its task, and I am sceptical that this effect was properly factored in by the Yugo tests.

The Yugo penetration criteria was the same as the US criteria at the time. 50+% of the mass passing through the armor 50% of the time. How the Germans measured the armor penetration of the projectile given their criteria methodology would be interesting.

The Yugo footnotes claim this round is for very fast moving lightly armored vehicles. Many people note that it has the same velocity as the PzGr 40 round, and speculate it would be a 'Ub' training round even though it isn't marked as such. It seems to be effective enough against the vertical side armor of the sherman.

[Yoozername]

It was actually meant for another thread. So I deleted it. Not sure what you are saying otherwise.

It was a pretty stilted translation. The version on page 205-206 of Muller & Zimmermann's Sturmgeschutz III V.1 flows much better and, if I knew the context of the original poster's reply, I could see if this made any difference to how it comes across.
Was it from a Norbert Szamveber book?

I am the original poster. Maybe best to put you on ignore?

[Mobius]

I did find some German data on this. In the Pak 40 Technisch Daten the weight is the same as the Pzgr. 40 of 4.4 kg.
The Pzgr. 40 has a muzzle velocity of 930 m/s. (The Pzgr. 39 has a MV of 750 m/s in this version.)

The penetration of the 40w is given as 77mm @ 100m and 56mm @ 1000m. Which would be at 30°.
So maybe I can work out a ballistic coefficient from these points.
[Edit]

I had more information on this round than I thought. I never wrote it up as I couldn't think of a reason why a tanker would use this round and have it take the place of a more potent round.
100m - 77mm, 500m - 69mm, 1000m - 56mm, 1500m - 38mm.

From German Anti-Tank [Panzerjager] Troops in World War II by Wolfgang Fleischer and Richard Eiermann.

[Yoozername]

I did find some German data on this. In the Pak 40 Technisch Daten the weight is the same as the Pzgr. 40 of 4.4 kg.
The Pzgr. 40 has a muzzle velocity of 930 m/s. (The Pzgr. 39 has a MV of 750 m/s in this version.)

The penetration of the 40w is given as 77mm @ 100m and 56mm @ 1000m. Which would be at 30°.
So maybe I can work out a ballistic coefficient from these points.
[Edit]

I had more information on this round than I thought. I never wrote it up as I couldn't think of a reason why a tanker would use this round and have it take the place of a more potent round.
100m - 77mm, 500m - 69mm, 1000m - 56mm, 1500m - 38mm.

From German Anti-Tank [Panzerjager] Troops in World War II by Wolfgang Fleischer and Richard Eiermann.

To be clear, these were only produced for the Pak 40? That is, not for the KWK 40 weapons or the StuK 40? No other caliber either I believe.

I could see the following rational for making these unique rounds...

There was a manufacturing ramp up issue with the PzGr 39 rounds for the weapons coming onboard in 1942. That is, the 7,5 cm KWK 40 (L43) and 7,5 cm StuK 40 (L43) and the Pak 40 [all shared the basic PzGr projectile}. The use of HL rounds was quite extensive from data people have posted here. Hollow charge ammunition is much cheaper to produce, often using existing high explosive shells as a basis, and offer a dual role as a HE expedient. They are not very good at range, have lower velocity than even normal HE (450 M/s vs. 550 M/s), and would be best used against stationary or immobilized enemy AFV. The VERY expensive PzGr 40 (Tungsten Carbide) ammunition had great benefits besides increased penetration. It was VERY fast and was a superior round to combat moving vehicles. Hence, using the 40W rounds was something that filled in some gaps. They were probably cheaper than even the HL to produce. They could be used to train gunners on PzGr 40 characteristics, and they could almost guarantee a first round hit at typical Pak 40 ranges.

The German gunners were told in no uncertain terms what ammunition to use in battle circumstances. I can supply reports.

I can see problems with having so many ammunition types also. From a training aspect, and the Germans probably trained many Pak 40 gunners, it would have been better to just have a couple of rounds to learn. As the PzGr 39 ammunition manufacturing reached consumption levels, it would be best to just concentrate gunnery on this round, with the SprGr/HL rounds being a secondary lesson. Since PzGr 40 rounds became almost nonexistent in 44-45, I doubt that the 40W was used much. An AFV like the Marder III could only haul around 27 rounds. I doubt they would want to carry anything other than just PzGr 39.

[Mobius]

Actually both the Technisch Daten for the 75/L43 and 75/L48 list this round [40(w)] at the bottom. This round starts off very fast but loses speed rapidly. It has a higher hit chance under 900m that pzgr. 39.

[critical mass]

When the 40W was designed, the changeover to pzgr39 did not yet finalized. This projectile may have been seen as an option in case they dont succeed in getting APCHE intactly through a sloped, high hardness plate, so that effect behind the plate could better be attacked with nonperforative or low perforative scabbing.
It also had a long reach compared to other options available at the Time. I remember that 40W were also produced for 75mm pak 41.
When the pzgr39 was abailable in quantity, the 40W was dropped for obvious reasons.

The penetrative efficiancy of the 40W is almost identic to soviel APBC against high hardness armor, which isnt surprising considering that both embrace the same failure mechanism by attacking the shear strength of the plate.

[Mobius]

When the 40W was designed, the changeover to pzgr39 did not yet finalized. This projectile may have been seen as an option in case they dont succeed in getting APCHE intactly through a sloped, high hardness plate, so that effect behind the plate could better be attacked with nonperforative or low perforative scabbing.
It also had a long reach compared to other options available at the Time. I remember that 40W were also produced for 75mm pak 41.
When the pzgr39 was abailable in quantity, the 40W was dropped for obvious reasons.

The penetrative efficiancy of the 40W is almost identic to soviet APBC against high hardness armor, which isn't surprising considering that both embrace the same failure mechanism by attacking the shear strength of the plate.

I don't know the history of this round but the cutaway illustration was added to the geschossringbush pamplet PDF
http://www.lexpev.nl/downloads/geschossringbuch.pdf in 4/43 while the pzgr. 39 was added 10/41. Also, it is not listed in the Merfblatt h.dv.481/77 of the 75mm PaK 40 7/42 while the Pzgr. 39 and Pzgr. 40 are listed.

I don't have a ballistic firing table but working from the penetration data to get velocity approximations the round really drops in speed over distance even with a ballistic cap like an APBC round. Mostly because the low weight gives it a low cross-sectional density.

Given the Yugo data I would not choose this round over the Pzgr. 39 at any time.

[critical mass]

The pzgr39 itselfe has a long story, with the requirements issued in 1940. Intended performances -in mass production- could only be met with composite Pzgr39 in 1942 and many old Pzgr. & Pz. K.Gr. rot were used 1942 to 1943 (TIGER units seem to have used flak Pzgr still in early 1943).
Only after heat treatments of monobloc Pzgr39 designs (75mm, 76.2mm, 88mm and 105mm (the latter only initially, as the change to the heavier 10.5cm L/4.3 Psgr for late war 105mm HV designs (10.5cm KWK L/70 and it´s derivative 10.5cm PzJK L/73 & 10.5cm KWK L/68 projects) prooved) were perfected in 1942, was that projectile also manufactured and service issued in any quantity (older, composite 50mm and 75mm Pzgr39 were available earlier than the monobloc´s, and some manufacturers kept producing these two piece designs even after 1942 because they were more tolerable to deviations in casting of the heat and subsequent heat treatments).
One has to keep in mind that the environment for AP requirements was extremely fluid in 1941 to 1943. Full calibre AP was just one of many options considered at this time, and some voices claimed it was going to be face obsolence caused by developments in HEAT and sub calibre APCR or APCNR.
The investigations in APSH projetciles just flanked this search for optimal solutions. It was, of course, later than Pzgr39 and Pzgr40 because the battlefield experiences demanding a look into high hardness armor failure mechanisms didn´t materialized before summer 1941*, I presume (my speculation) that the capture of the very soviet AP ammo has some contribution here, too, which the germans initially failed to understand**.
Again, these projectiles are good spall inducers on overmatched, highly sloped, high hardness plating, though not necessarely against more ductile, softer plating or when complete penetration was required.

*the polish, I think, looked already earlier into this for their anti tank rifles using soft cored AP to exploit shear failure. This makes sense because thin armor plating, which these anti tank rifles intended to defeat, were also treated to high hardness and the plate gives in to whatever type of resistence (shear or plastic deformation) is weaker. However, previous to the T34, nobody was employing high hardness plating in relatively thick plate sections, and this, too, triggered all kind of investigations.

**In tests, these APBC-HE projectiles always broke up on any discriminate target plate, and this rendered the explosive filler and fuze action always ineffective, even if the fuze would have been better than the TM5 ones they saw. The high De Marre K used in soviet AP calculations reflect this behavior of these deformable, breakable projectiles. When the germans calculated penetration based from soviet documents, these values only reflect performance vs soviet HH plating under onditions of plug ejection and projectile break up, and may be inadaequate against german RHA.

I wouldn´t be too surprised if the ballistic of the Pzgr40W and Pzgr41W were matched to their respective Pzgr. 40/41(Hk) variants. Identic contour lines, weight and initial velocities imply a potential ballistic matching.

[Yoozername]

One source claims that the KWK 40/StuK 40 ammunition production, using the 40W rounds, amounted to ~75 thousand rounds. Started in 1942 and apparently ending in 1943. Really a small amount considering that PzGr 39 was 1,9 million in 1943.

[critical mass]

official instructions state that the -40W /-41W (Weicheisenmunition) ammunition had:

-identic ballistic properties to the -40 and -41(Hk.) ammunition
-less penetration
-more effect than pzgr40 (hk.) within the target due to larger induction of discing failure and spall but less effect than pzgr.39 bursting in target.
-is cleared by 1944 to be used up as training ammunition (manufacture has ceased)

Pzgr40(W) PAK40 penetration at 60°(i.V.: 930m/s):
100m: 77mm
500m; 69mm
1000m: 56mm
1500m: 38mm

Pzgr41(W) PAK41 penetration at 60° (i.V.: 1230m/s):
100m: 86mm
500m: 78mm
1000m: 67mm
1500m: 53mm

source: BAMA RH12-2-175

[Yoozername]

Interesting report regarding the on-coming KWK 40/StuK 40/Pak 40 weapons and ammunition issues...

Notification by Generalmajor Gustav Harteneck (2.AOK) to his subordinates dated 17.6.1942 warning of the extreme shortage of ammunition in front for anti-tank guns (7.5 cm Pak40) as well as for tank guns (7.5 cm KwK40).

The level of production allows, currently and temporarily, only a very small supply of ammunition for the new heavy anti-tank guns as well as tank guns. In the coming months, and only in the best of cases, will be able to supply these weapons with basic equipment, in most cases even smaller.

The Fuehrer, aware of this situation, has ordered and so the delivery to the troop of these weapons. Even with basic ammunition equipment, these weapons are called to play a fundamental role in the fight against Russian heavy tanks.

The troop must be made to understand this directive. Every troop leader, as well as any battery chief, must understand that from now on, the condition for heavy antitank weapons to play a decisive role, is that they will only be used against heavy Russian tanks and only in those cases where that at short distances can not be fought with 5 cm anti-tank guns. That is, they will only be used to attack the front of the T-34, KW I and II; these vehicles can be destroyed by their sides with the 5 cm anti-tank gun.

Skillful positioning as well as the camouflage of heavy anti-tank guns is of great importance. To improve the performance of the barrel and in relation to its position, we must try to approch natural barriers in the terrain that hinder the tank. Likewise, Panzer IV vehicles as well as assault guns equipped with the KwK 40 cannon must adapt to the shortage of ammunition. We must also take into account that in the coming times the Panzer III and the Panzer IV with long cannon and the Sturmgeschütz 40 will have a very small figure of fragmentary ammunition of high explosive ( Sprenggranaten ).

At present, the heavy anti-tank guns and the aforementioned tanks and assault guns can be equipped, depending on the model, with ammunition equipment of between 70 and 150 projectiles per cannon; of them between 30 and 50 will be perforating point projectiles ( Panzergranaten ). This basic equipment will be complemented slowly and progressively. It is prohibited to make requests for ammunition repeatedly.

All communication referring to this topic at the higher level of division will only occur orally; This order once read must be destroyed.

[critical mass]

I noticed a little piece of information in BAMA RM 7-1248 for the 75mm Pzgr.39:

(...) 7.5 cm Panzergranate 39 des Heeres in Frage. Hierbei auf folgendes hinzuweisen:
A) Zuender spricht erst bei Panzerstaerken 15 - 20 mm an"

-1SKL 21589/44 gKdos.

The fuse activates only when engaging armor plate of 15 to 20mm minimum thickness.

[Contender]

I thought German APCBC fuses are triggered by the impact irrespective of armor thickness? The impact would trigger the fuse which in turn trigger a minimum delay of .003 seconds before the fuse would finally set off the explosive filler.

[critical mass]

Any base detonating delay fuse requires a strong enough impact shock to trigger the primer.I suppose 20mm are required at close to normal and the thinner range, 15mm, at high obliquity.

[Mobius]

Any base detonating delay fuse requires a strong enough impact shock to trigger the primer.I suppose 20mm are required at close to normal and the thinner range, 15mm, at high obliquity.

So not so good against halftracks and AT guns.