German discarding sabot rounds

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Yoozername
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Re: German discarding sabot rounds

Post by Yoozername » 27 Oct 2017 19:48

Excellent stuff here.

When did the Germans become aware of the British use of the discarding sabots?

I googled this...

http://www.bbc.co.uk/history/ww2peoples ... 7506.shtml

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Mobius
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Re: German discarding sabot rounds

Post by Mobius » 30 Oct 2017 12:57

critical mass wrote:
Are there any penetration charts
12.8cm PAK44/KWK44: The elevated velocity finally significantly enhanced the 12.8cm PAK44/Kwk44 firing 12.8cm Pzgr39TS, firing a 8.8cm Pzgr 39 in it´s sabot at a muzzle velocity of 1230m/s. ....
30° penetration at 1000m: 264mm RHA*; 2000m: 230mm RHA*
Do you have the impact velocities at these ranges?

critical mass
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Re: German discarding sabot rounds

Post by critical mass » 30 Oct 2017 15:37

This source does not contain information about the terminal velocity at range for the 12.8/8.8cm Pzgr 39 Ts.

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Mobius
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Re: German discarding sabot rounds

Post by Mobius » 31 Oct 2017 16:34

An approximation of terminal velocities can be made by using the graph on post #82 and the penetration values.

If the 128mm Pzgr39 TS just had the deviation of the 15cm Pzgr39 TS for sFH18: (50% zone of impacts at 1000m: Höhe: 50cmm, Seite: 57cm) it would be the most accurate shell (taking into account realistic range estimation) I can find used in WWII.

critical mass
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Re: German discarding sabot rounds

Post by critical mass » 06 Nov 2017 20:08

For what´s worth, I have some data on late ww2, fin stabilized heat projectiles (15cm HL/Ausf. C mit Klappleitwerk) for sFh18. Penetration was 210mm @ 30°, 165mm @ 45° and 125mm @ 60° (independent of range). Accuracy for 50% zone was 0.66m x 0.38m at 500m and 1.18m x 0.84m at 1000m.
So apparently, the 15cm Psgr 39 Ts. was more accurate at long range.

source: I/77348/44g, dated 9th of sept. 1944.


Edit.
I can now confirm that 12.8cm/8.8cm Pzgr T.s. covered in this thread was ordered to be developed as the intended ammunition for 12.8cm KWK L/55 with the MAUS explicitely mentioned. I hope this will put finally an end to the discussion whether or not they could be fired by MAUS.
Primary source: 38417/43g. Dated 16th of sept. 1943.

I quote:
"12.8cm: Günstigstes Unterkaliber 8.8cm. Mehr als 20%ige Lesitungssteigerung ist sicher. Krupp und Rheinmetall haben Bedenken bei der 12,8cm K40 hinsichtlich der Stabilität. Vorschlag: 10,5cm Unterkaliber. B.V. [my note: Bochumer Verein] geht von 12,8cm KWK L/55 (Maus) aus. Entwicklungsaufträge: siehe Vorderseite."
Both, Kruppe Rheinmetall and Bochumer Verein received contracts to deliver 50 specimen 12,8cm/10,5cm Pzgr Ts (Krupp) and 12,8cm/8,8cm Pzgr Ts (B.V.).

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Re: German discarding sabot rounds

Post by Paul Lakowski » 07 Nov 2017 02:39

I wonder how accurate such AAA ammo would be at altitude?

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Re: German discarding sabot rounds

Post by Yoozername » 07 Nov 2017 03:51

It would depend on how you define accuracy in that situation. Striking a bomber? Getting with the fragmentation spread an acceptable distance to a bomber? Firing at vertical trajectories involves greater parameters such as wind and air transitions. A thousand yards is 3000 ft. bombers might be 10X that distance.

I have read that the Germans investigated using sabot rounds in a AA role, but the decrease in diameter means much less fragmentation, and when firing at targets in thin air, it is the fragmentation that is the payload. The blast effects are minimal. Evidently, the Germans never implemented it. And I don't think anyone else tried or used it either.

critical mass
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Re: German discarding sabot rounds

Post by critical mass » 07 Nov 2017 18:09

This is a tabulation dated 29th of sept. 1944, summerizing the development of all -Ts. projectiles and a comparison with normal full calibre projectiles.
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Re: German discarding sabot rounds

Post by critical mass » 27 Nov 2017 22:27

Attached below is a well known graph from ADM 213-951 detailing the penetration characteristics of various german AP projectiles.
The curves given therein are difficult to read so I emphasized the relevant points in the graph attached to this memo.
This is not a german primary source penetration chart but rather a secondary translation of other german primary data conducted post war by the british. There is a slight offset between this curve and official german WaPrüf curves I have seen.

For each projectile, two lines are drawn, one solid line and a dotted one. The curves represent the usual 5/5 successful penetration criterium G(D), and the type of the line indicates whether or not the projectile is for intact [=G(D) heil] or for broken projectiles [=G(D) grenz].
Those who are less familar with what these curves mean and how they were derived can make mistakes at this point in interpretation.
The authors of this graph, already an interpretation of other, primary data and curves, added two reference lines to indicate the general behavior of the projectiles. The first one intersects the 8.8cm curve at 970m/s and 180mm @30° -roughly at where late ww2 service acceptance specification ballistic trials were to be conducted.
Consequently, it´s curve details that 2/3 of the mass produced shells will remain intact. Interpretors, who are unfamilar with service acceptance proof specifications may fell victim to possible false interpretations here.

viewtopic.php?f=47&t=231147

During service acceptance proof (1944), two projectiles of each lot were tested against the 18cm plate, and if both penetrated AND remained intact, the lot was passed. If one projectile failed to stay intact (or to penetrate), another projectile was choosen which had to pass or the lot was rejected. Thus 2/3 is the absolute minimum confidence level. A worse projectile quality would not be tolerable for service acceptance.
Consequently, an arrow is placed on the line, directing towards higher velocity realms.

It´s important to understand that the yellow marked field is an area of reducing likelyhood of the mass produced AP to stay intact rather than a finite border. At a 1110m/s velocity point, the 8.8cm curve changes from solid line to dotted line. This is somehow earlier than the 1175m/s 2nd intersecting curve, which details that only good quality projectiles will remain intact. Again, it is another field of reducing likelyhood, not a finite borderline. Dr. Wagenknecht testifies that for his mass produced 8.8cm Pzgr39, the projectile stays intact until 1250m/s while at >1300m/s it regularely breaks up. One test is given against a 305mm RHA plate @30° and 1280m/s which the projectile penetrated intact. I presume this latter case is an exceptional performance.
Notice that the mean between 970m/s (lower limit of staying intact) and 1250m/s (upper limit of staying intact, barring a fluke) is exactly 1110m/s -and this is exactly where the 8.8cm Pzgr 39 curve changes from solid to dotted curve. Rather than a coincidence, I cautiously postulate that these penetration graphs show the 8.8cm penetration performance with the 50% confidence level of staying intact. With other words, at velocities past the point where intact performance is to be expected, only average performances are shown. Further confirmation is necessary.

By adding the 305mm trial datapoint from the Hillersleben trial, it´s possible to reconstruct a penetration graph for an intact projectile up to very high, terminal velocities, such as will be encountered by 12.8cm/8.8cm Pzgr Ts at short range. As can be seen, there is a growing delta between intact and broken penetration. These delta´s can also be found in other penetration charts, such as g.K.dos100 naval AP seperating intact and broken penetration or the penetration curves for old pattern 7.5cm Pzgr Gg rot (break up) and new pattern 7.5cm Pzgr 39 (no break up) in Lilienthalreport 166.
At velocities below 970m/s / 180mm thickness and for the 8.8cm projectile, both curves fall together and the projectile stays always intact, whether it penetrates or rebounds. At higher velocities, more and more of the mass produced shells experience break up causing a delta between penetration of intact and broken projectiles. This delta has it´s root in break up processes of the projectile. Initial break up effects of a high quality 8.8cm Pzgr 39 variety shell in thick RHA are very specific. Due to the high nose hardness (Rc61) and almost equally high core hardness (Rc60), the nose of the projectile can´t compress, or deform sideways and fractures only when very high stresses are encountered. However, down the body of the projectile, the hardness drops towards he base, which is the first part of the projectile to experience damagign effects in thick plates (>1 plate/cal) due to a strong, sideways directed base slap experienced by the projectile while it attempts to exit the plate´s back (the primary location for the phenomenon of "normalization"). This force hits the projectile where it isn´t that hard (Rc 30) and less tolerable to impact due to a smaller section thickness caused by the explosive cavity. Crack can propagate to the adaptor or cavity but this damage has -initially- little effect on the critical velocity for a given plate thickness due to the fact that the hard nose already did it´s job in creating a hole large enough for the projectile to pass before the base failed. However, at higher triaxial stress levels, requiring higher velocities and correspondingly thicker plates (or worse projectile quality, whatever fails first), the cracks quickly extend up to the fwd bourrolet and can split the projectile up, or worse, deform it. This will raise the critical velocity compared to an undeformed penetrator considerably because the deformed, inhomogene section area projectile now needs to exert more work for plastic deformation of the larger hole in the armor plate.

The graph not only includes the regular 8.8cm AP but also an 9.93kg sabot with 8.8cm core which is within 7g of the weight reported from 12.8cm/8.8cm Pzgr Ts (vereinfachte Fertigung) in the sources. With this curve, and the reconstructed one presented here for "intact" penetration, it´s possible to quantify penetration differences for both, broken (50% confidence level) and intact condition of the 8.8cm Pzgr sabot projectile.
Of course, a very poor performing 8.8cm Pzgr, experiencing break up already at 180mm / 970m/s would start to deviate from the intact curve earlier and thus, will eventually obtain significantly less penetration at very high velocity than a higher quality projectile which experiences break up at 1110m/s- and less even than a projectile which manages to stay intact.
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Re: German discarding sabot rounds

Post by MH4UAstragon » 13 Feb 2018 19:38

@critical mass

Hello there, I’ve been seeing this thread for awhile now trying to get accurate source material on this particular topic. Specifically the 105mm guns on the Sturmpanzer and Brummbar, and the 128mm guns on the Jagdtiger & Maus.

Could you post a link to that 406-page Rh-8-1326 document?

I’m trying to see if I could use that to get such rounds modelled in the online MMO War Thunder.

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Re: German discarding sabot rounds

Post by BaronTiberius » 13 Feb 2018 21:00

critical mass wrote:This presumption is a correct one, they indeed used 7.5cm Pzgr39 for 105mm and 88mm Pzgr39 for both, 150mm and 128mm Sabot AP.
Do you have access to the full report?

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Re: German discarding sabot rounds

Post by critical mass » 14 Feb 2018 10:13

I am not certain which document exactly Your question refers to. As You may have noticed, I have provided material from various reports for this discussion.

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Re: German discarding sabot rounds

Post by MH4UAstragon » 14 Feb 2018 12:47

critical mass wrote:I am not certain which document exactly Your question refers to. As You may have noticed, I have provided material from various reports for this discussion.
I’m looking for an online scan of “Übersicht über TS-Geschosse im Vergleich zu Normalgeschossen" dated 29th of sep. 1944 that you mentioned, since it details quite a few shell types for which there are a good many guns already implemented in the MMO War Thunder.

Also, @Radar, could you try and post that document from which all those pictures were sourced?

critical mass
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Re: German discarding sabot rounds

Post by critical mass » 15 Feb 2018 20:31

Ok, I understand what You are looking for. That beeing said I am in posession of the complete document but after reading the policies of WT, I decide to reject sharing the whole document for the reason that it would be required to be publicly available. I am unsure whether or not sharing the complete document would infringe third party interests. The document is available via BAMA Freiburg (BAMA RH-8-1326). If I would shar the document it would be only under the condition not to share it publicly.

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Re: German discarding sabot rounds

Post by MH4UAstragon » 22 Feb 2018 14:27

critical mass wrote:Ok, I understand what You are looking for. That beeing said I am in posession of the complete document but after reading the policies of WT, I decide to reject sharing the whole document for the reason that it would be required to be publicly available. I am unsure whether or not sharing the complete document would infringe third party interests. The document is available via BAMA Freiburg (BAMA RH-8-1326). If I would shar the document it would be only under the condition not to share it publicly.
Well based on the bug reporting process of War Thunder, excerpts from it would be posted in the report and the link to the report would be posted at the bottom of the bug report.

So I don’t actually know how to properly link it there without making it non-public. Any ideas?

Also, regarding the K.w.K.40 experimental long-dart-shaped rounds (can’t spell the name right), what source document, if any, has actual penetration data on those? Because the KwK40-armed Panzer IV and StuG III models in the game are rather undertiered, and the availability of such rounds could be a way to properly tier them in said game.

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