8,8 cm PzGr 39 Performance

[Mobius]

Published in 1939, the FT 125 for the Model 39 gun lists these striking velocities using the BR 350A projectile of 6.3 kg. with a MV of 662 m/s:
100 meters 651 m/s
300 meters 631 m/s .
500 meters 611 m/s
1000 meters 564 m/s
1500 meters 519 m/s
2000 meters 478 m/s
2500 meters 440 m/s
3000 meters 404 m/s
3500 meters 372 m/s
4000 meters 345 m/s

Thanks Miles. Very similar to the firing table I posted of the BR-350 which was ~6.5 kg. It does make one wonder if they had the right shell in that.

[critical mass]

The PDF can be downloaded from here:
https://digitalcommons.unl.edu/dodmilintel/66/
On page IV the weight is given as 14.3 lb. which is 6.486 kg. The Russians give the BR-350 kg as 6.5 and the BR-350A as 6.3 kg. The later BR-350B is also 6.5 kg.
Here's a link to the Model 39 on a Russian site.
https://ru.wikipedia.org/wiki/76-мм_див ... года_(УСВ)

Yes, You are right. Mea culpa.

[Peasant]

So, about point blanc penetration of this shell. The following analysis suggests that it shouldnt be capable of reaching the much quoted performance of 203mm/30° at 100m (990m/s) even against very soft 70kg/mm^2 (203BHN circa) plate.

[critical mass]

Notice two differences:
A) The 8.8cm Pzgr.39 had a lighter cap than the 75mm Pzgr.39.
B) the 7,5cm Pzgr.39 had a blunter nose shape than the 88mm Pzgr.39

It follows from A) and B) above that If the 8.8cm Pzgr 39 stays intact (only then), it should be naturally expected to perforate more armor than the 7.5cm Pzgr.39.
On the other hand, I suppose the 75mm Pzgr39 is more capable of staying intact against more difficult targets and higher velocities.

[peeved]

Judging by the fuze threads the 8,8 cm would have a percentually thicker base when fuzed than 7,5 cm PzGr 39 (of course the fuze doesn't screw all in but still the 8,8 would appear to be the thick-bottomed one). Would that have any bearing on AP shell integrity and relative penetration?

Markus

[L/24Stug]

Perhaps scaling both at the same proportion may help to compare their size.

75-88.jpg

[Peasant]

This talk reminded me about the old project of mine, about studying the influence of shell's nose shape on its ballistic performance. I've cleaned the dust from my old files and used the functions to generate profiles of both these shells, so I'm leaving this here, might be interesting to see:

[Avalancheon]

Notice two differences:
A) The 8.8cm Pzgr.39 had a lighter cap than the 75mm Pzgr.39.
B) the 7,5cm Pzgr.39 had a blunter nose shape than the 88mm Pzgr.39

It follows from A) and B) above that If the 8.8cm Pzgr 39 stays intact (only then), it should be naturally expected to perforate more armor than the 7.5cm Pzgr.39.
On the other hand, I suppose the 75mm Pzgr39 is more capable of staying intact against more difficult targets and higher velocities.

Didn't you once say that the Germans changed the specifications of the 75mm Pzgr 39 in 1944? [] That they proof tested it up to angles of 45 degrees?

I'm guessing that in order to achieve this, they would have needed to alter the shape and thickness of the cap.

So when you say that the 88mm shell had a lighter cap than the 75mm shell, which batch are you referring to? The 75mm shells that were proof up to 30 degree or 45 degree angles?


[] This was the thread: viewtopic.php?p=2191974#p2191974

[Yoozername]

Perhaps scaling both at the same proportion may help to compare their size.

75-88.jpg

The 88mm is 'lighter' in regards to the cap is acually not that thick at the center. Cleearly two different designs. Does anyone know if these caps are cast or machined? I would think they are castings that are treated.

[critical mass]

Didn't you once say that the Germans changed the specifications of the 75mm Pzgr 39 in 1944? [] That they proof tested it up to angles of 45 degrees?

I'm guessing that in order to achieve this, they would have needed to alter the shape and thickness of the cap.

So when you say that the 88mm shell had a lighter cap than the 75mm shell, which batch are you referring to? The 75mm shells that were proof up to 30 degree or 45 degree angles?


[] This was the thread: viewtopic.php?p=2191974#p2191974

The specifications refer to proof angle for proof of lots of service proectiles. No change of projectile geometry was involved here to the best of my knowledge. The only aspect which was subject of modification was the shell steel and heat treatment of the projectile body.

A high quality Pzgr.39 was capable to perforate roughly cal/RHA plate at 45 to 50 degrees intactly ft to burst. However, a poor quality shell would break up at 40° or even less. There is a scatter in projectile quality caused by tolerances in heat treatment of the individual sub contractors. The new proof specifications could only be obtained by applying much tighter heat treatment tolerances, of the AP-cap, the shell body and the fuse threads. The alloy composition of the shell steel just provided potential hardenability, it was the subsequent heat treatment, which transformed the potential into discrete physical properties.

Its somehwat the progress of metallurgical skill allowing improvements. The first Pzgr.39 were high quality if made by special labs in low quantities, for research purposes. It required the welded on nose tip to make mass production of the product feasable. By late 1942, Döbener Gusstahlwerke finnished its work on heat treatment and research of monobloc Pzgr. 39 shells with the same or higher quality than the welded on tipped versions. This was applied throughout 1943 in mass production over a wide scale. It was already recognised in the Lilienthalreport 166 (dated 1943) that this Pzgr.39 was capable of perforating 45° intact and a new proof specification was intended for the future. Work then commenced to improve heat treatement of the fuse holders, shoulder and base of projectile so that mass production Pzgr.39 would have a good chance to pass the raised proof.

btw., the AP-cap was sort of stamped into form. It´s not a cast element, it´s closer to forging into preshaped matrices.

[Peasant]

Great info. This answers a few questions I've been wondering about for a long time.

[Avalancheon]

The specifications refer to proof angle for proof of lots of service proectiles. No change of projectile geometry was involved here to the best of my knowledge. The only aspect which was subject of modification was the shell steel and heat treatment of the projectile body.

A high quality Pzgr.39 was capable to perforate roughly cal/RHA plate at 45 to 50 degrees intactly ft to burst. However, a poor quality shell would break up at 40° or even less. There is a scatter in projectile quality caused by tolerances in heat treatment of the individual sub contractors. The new proof specifications could only be obtained by applying much tighter heat treatment tolerances, of the AP-cap, the shell body and the fuse threads. The alloy composition of the shell steel just provided potential hardenability, it was the subsequent heat treatment, which transformed the potential into discrete physical properties.

Its somehwat the progress of metallurgical skill allowing improvements. The first Pzgr.39 were high quality if made by special labs in low quantities, for research purposes. It required the welded on nose tip to make mass production of the product feasable. By late 1942, Döbener Gusstahlwerke finnished its work on heat treatment and research of monobloc Pzgr. 39 shells with the same or higher quality than the welded on tipped versions. This was applied throughout 1943 in mass production over a wide scale. It was already recognised in the Lilienthalreport 166 (dated 1943) that this Pzgr.39 was capable of perforating 45° intact and a new proof specification was intended for the future. Work then commenced to improve heat treatement of the fuse holders, shoulder and base of projectile so that mass production Pzgr.39 would have a good chance to pass the raised proof.

btw., the AP-cap was sort of stamped into form. It´s not a cast element, it´s closer to forging into preshaped matrices.

Wow, great answer. You really know your stuff.

After reading your comments here and in the other thread, I now see the importance of preventing damage not just to the nose of the projectile, but to the base of the projectile as well. As you said, when an AP shell hits a sloped armor plate, the projectile will be turned upward, which slams the base of the projectile against the plate. This has the potential to damage the shell and render the fuze inert.

The 75mm Pzgr 39 got a performance boost by more careful heat treatment of the shell body, rather than any geometric changes to the shell itself. The fundamental design was so sound that it did not need to be changed at all. That really shows just how advanced the Germans were in their knowledge of ballistics.

The Pzgr 39 shell almost qualifys as a kindof wunderwaffe. Arguably, it had more of a battlefield impact than alot of the other inventions that are called wunderwaffe. The projectile is just so much better designed than any of the stuff the Soviets, British, or Americans were using at the time. Soviet AP shells especially stand out for their poor quality.

Its kindof amazing that the 75mm Pzgr 39 can hit at these kindof velocitys and obliquitys without shattering or breaking up. Not only that, but they can actually penetrate the plate while remaining in a condition fit to burst! Thats the kindof performance that Allied ammunition could never achieve.


P.S. Just a small question, but what was the Döbener Gusstahlwerke?

[critical mass]

I have never taken Wunderwaffe serious. From what I can gather, I get the impression that the Prussians and Germans always went for technical solutions to their social problems. This was both, the constituent and the Modus operandi. The function of WW falls exactly here, to keep up social support for a lost conflict.

The pzgr.39 was different. It’s Areal Instrument of warfare, not a vague concept to keep social unrest at bay.

[Avalancheon]

I have never taken Wunderwaffe serious. From what I can gather, I get the impression that the Prussians and Germans always went for technical solutions to their social problems. This was both, the constituent and the Modus operandi. The function of WW falls exactly here, to keep up social support for a lost conflict.

The pzgr.39 was different. It’s Areal Instrument of warfare, not a vague concept to keep social unrest at bay.

The Germans did use wunderwaffe in a ploy to maintain support for a lost cause, with the V-1 and V-2 being the most obvious examples. But I was never aware that the Prussians had done the same thing. I struggle to imagine what would qualifty as a wunderwaffe. Perhaps the Dreyse needle gun?


Anyway. I have been wondering for some time, what kindof protection the different variants of the Sherman tank could offer against 75mm Pzgr 39? Specifically, what kind of protection could the glacis plate offer?

The M4 had a 51mm thick plate sloped at 56 degrees. It was RHA.
The M4A1 had a 51mm thick plate sloped at 56 degrees. It was cast armor.
The M4A3 had a 63mm thick plate sloped at 47 degrees. It was RHA.

The M4A1 must surely be the most vulnerable. Cast armor is inferior to RHA, particularly against oblique impacts.

As far as LOS thickness goes, the glacis of the M4 and M4A3 are both comparable to each other.

[Contender]

The M4A1 had a 51mm thick plate sloped at 56 degrees. It was cast armor.

To add to this the widely used late M4A1 armed with the 76 mm weapon was 63 mm @ 47° (cast armor).

Also the ~51mm (aka 50.8 mm) Sherman glacis plates were multi-piece & had some cast armor elements:

which later they applied plates over as stop gap measure: