German discarding sabot rounds

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
critical mass
Member
Posts: 678
Joined: 13 Jun 2017 14:53
Location: central Europe

Re: German discarding sabot rounds

Post by critical mass » 22 Feb 2018 17:00

I am afraid that I am not much into gaming at all. I am also not convinced that historical details are a precondition for enjoyable gaming experience. From my understanding- the PzIV / StuG would unlikely to ever receive one. For what´s worth, one of the secondary sources attributes the 7.5cm subcalibre AP-Pfeilgeschoss to the 75mm secondary gun of MAUS, however, I cannot comment on that because I don´t know exactly which document Fröhlich was refferring to. I have never seen any reliable penetration data for those projectiles, too.

MH4UAstragon
Member
Posts: 23
Joined: 13 Feb 2018 19:32
Location: Eastern USA

Re: German discarding sabot rounds

Post by MH4UAstragon » 22 Feb 2018 18:41

critical mass wrote:I am afraid that I am not much into gaming at all. I am also not convinced that historical details are a precondition for enjoyable gaming experience. From my understanding- the PzIV / StuG would unlikely to ever receive one. For what´s worth, one of the secondary sources attributes the 7.5cm subcalibre AP-Pfeilgeschoss to the 75mm secondary gun of MAUS, however, I cannot comment on that because I don´t know exactly which document Fröhlich was refferring to. I have never seen any reliable penetration data for those projectiles, too.
Let’s just say the ingame Maus is a joke right now. People migrating over from World of Tanks to War Thunder freak out when they see a Maus, but anyone not scared of it knows immediately where to shoot it. It’s so badly broken even a 1943 IS-2 can frontally pen its turret cheeks.
- incorrect turret armor thickness of 220mm cast, equating to 208mm RHAe, with some “bad steel modifier” dropping it down to about 195mm effective.
- incorrect steel type on the whole tank.
- incorrectly slow turret traverse rate of 5-8 degrees per second
- incorrect hull traverse rate and complete lack of hull traverse while on the move (the Ferdinand ingame has the same issue, I have no idea if that’s correct on that either)
- possibly too long of a reload, between 18 and 24 seconds
- incorrect pen on the APC-HE and APCBC-HE of 266mm and 269mm vs flat plate
- incorrect main gun velocity from not using the heaviest propellant charge in the modelling of the gun
- incorrectly thin engine ventilation sections on the top of the hull, allowing even .50cals to punch through and light the thing on fire
- lack of the tank’s intended 20mm coaxial anti-air/infantry gun.
- incorrect penetration on the 75mm coaxial HEAT rounds, both less than real figures I’ve seen
- lack of the experimental APHEDS rounds discussed in this forum thread.
- and ontop of all that it’s overtiered to the point where every tank it could ever normally see can frontally pen the turret.

And next patch might make it even worse.

User avatar
Mobius
Member
Posts: 595
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: German discarding sabot rounds

Post by Mobius » 23 Feb 2018 00:51

MH4UAstragon wrote:- incorrect turret armor thickness of 220mm cast, equating to 208mm RHAe, with some “bad steel modifier” dropping it down to about 195mm effective..
It is curved though this sort of makes a shell trap on the lower half of front turret. Well cast has a bit lower resistance than RHA but this sort of disappears in thick armor. But bad steel modifier would apply more to RHA as there aren't many examples of very thick cast to go by.
MH4UAstragon wrote: - incorrect pen on the APC-HE and APCBC-HE of 266mm and 269mm vs flat plate.
That sounds about right to me. A average of data sets produces 265mm at 185m.

MH4UAstragon
Member
Posts: 23
Joined: 13 Feb 2018 19:32
Location: Eastern USA

Re: German discarding sabot rounds

Post by MH4UAstragon » 23 Feb 2018 01:48

Mobius wrote:
MH4UAstragon wrote:- incorrect turret armor thickness of 220mm cast, equating to 208mm RHAe, with some “bad steel modifier” dropping it down to about 195mm effective..
It is curved though this sort of makes a shell trap on the lower half of front turret. Well cast has a bit lower resistance than RHA but this sort of disappears in thick armor. But bad steel modifier would apply more to RHA as there aren't many examples of very thick cast to go by.
MH4UAstragon wrote: - incorrect pen on the APC-HE and APCBC-HE of 266mm and 269mm vs flat plate.
That sounds about right to me. A average of data sets produces 265mm at 185m.
All I’ve heard regarding cast plating is that any difference to RHA ceases to exist past a certain thickness, it was some US source saying past 160-180mm cast plate behaved like rolled plate.

As for the shell penetration numbers, those are seen in sources as the numbers for penetration in German tests - against RHA sloped back 30 degrees, not vs flat plate. What War Thunder pulled was pasting in the numbers from those tests as the values against flat plate. This is objectively wrong, but was deemed okay back when the thing was added initially. Now though with a slew of crazy postwar stuff in said game, artificial nerfs like that aren’t needed any longer.

Sorry, I don’t want to derail this thread too much about the game I play.

critical mass
Member
Posts: 678
Joined: 13 Jun 2017 14:53
Location: central Europe

Re: German discarding sabot rounds

Post by critical mass » 23 Feb 2018 12:57

MAUS turret front plate was a 240mm nominal Wh/n.A. RHA plate, bend to a curved shape. Usual tolerance range in thickness is -0% and +5%, however, due to the bending, it maybe be somehow thinner than 240mm in certain arc sections.
Cast armor always is inferior to RHA if made to the same quality standarts due to present impurities which remain as local weakness and cannot be cross rolled out. This was exactly the reason why the soviet´s changed back from thick cast turret armor to RHA turret armor in the late 1960´s turret deisgns.
However, when very thick, RHA and cast armor alike should be made softer to counter for increasing centre section, temper induced brittleness due to differential /too slow cooling rates of a thick plate´s centre.

128mm L/55 penetration (service AP Pzgr 43) was 228mm rated (5/5, intact) at 100m and 30° plate. 50% criterium would be 238mm RHA (80kg/mm^2) at 100m and 30°.
0° tests weren´t made but according to WaPrüf´s own angle modifier tabulations, the 5/5 performance should be 1.23 times that of 30° =280mm (100%) or approx. 294mm RHA (50% success) at 100m.

User avatar
Mobius
Member
Posts: 595
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: German discarding sabot rounds

Post by Mobius » 23 Feb 2018 17:05

critical mass wrote:0° tests weren´t made but according to WaPrüf´s own angle modifier tabulations, the 5/5 performance should be 1.23 times that of 30° =280mm (100%) or approx. 294mm RHA (50% success) at 100m.
Going over to your post of the 15cm Pzgr. L/3.7 zu 45,5 kg graph. Do the lines represent this modifier or are they just a multiple of the 1/cosine? Because they look like at the 30 degree mark it is only about 1.17 times above the 0 degree mark.

seppw
Member
Posts: 106
Joined: 24 Dec 2017 00:49
Location: Central Europe

Re: German discarding sabot rounds

Post by seppw » 23 Feb 2018 20:57

critical mass wrote:MAUS turret front plate was a 240mm nominal Wh/n.A. RHA plate, bend to a curved shape. Usual tolerance range in thickness is -0% and +5%, however, due to the bending, it maybe be somehow thinner than 240mm in certain arc sections.
Cast armor always is inferior to RHA if made to the same quality standarts due to present impurities which remain as local weakness and cannot be cross rolled out. This was exactly the reason why the soviet´s changed back from thick cast turret armor to RHA turret armor in the late 1960´s turret deisgns.
However, when very thick, RHA and cast armor alike should be made softer to counter for increasing centre section, temper induced brittleness due to differential /too slow cooling rates of a thick plate´s centre.

128mm L/55 penetration (service AP Pzgr 43) was 228mm rated (5/5, intact) at 100m and 30° plate. 50% criterium would be 238mm RHA (80kg/mm^2) at 100m and 30°.
0° tests weren´t made but according to WaPrüf´s own angle modifier tabulations, the 5/5 performance should be 1.23 times that of 30° =280mm (100%) or approx. 294mm RHA (50% success) at 100m.
You meant "in the late 1990s", right? At least the T-90 did: T-90A from 1999

critical mass
Member
Posts: 678
Joined: 13 Jun 2017 14:53
Location: central Europe

Re: German discarding sabot rounds

Post by critical mass » 23 Feb 2018 21:48

Mobius wrote:
critical mass wrote:0° tests weren´t made but according to WaPrüf´s own angle modifier tabulations, the 5/5 performance should be 1.23 times that of 30° =280mm (100%) or approx. 294mm RHA (50% success) at 100m.
Going over to your post of the 15cm Pzgr. L/3.7 zu 45,5 kg graph. Do the lines represent this modifier or are they just a multiple of the 1/cosine? Because they look like at the 30 degree mark it is only about 1.17 times above the 0 degree mark.
The Gkdos100 graphs are based upon firing trials, but smoothed out. The effect is substantially larger than 1.17 attributed by You, at least at realistic, terminal velocities:
700m/s
60° = 150mm
90° = 205mm
figure of merit 90°/60°: 1.37

500m/s
60° =104mm
90° =143mm
figure of merit 90°/60°: 1.37

Of course, when dealing with 15cm projectiles, one needs to take into account the large scaling effects, which have significant impact.
With 5cm Pzgr39 trials, the 90°/60° difference wasn´t that large: 1.15. With 7.5cm Pzgr39 it was already 1.23, the figure for 15cm from GKdos100 graphs (1.37) does fit the same trend, which describe the scale effect. For what´s worth, the trend implies for 88mm = 1.25 and for 128mm = 1.33, more data is necessary to verify these figures.

.
You meant "in the late 1990s", right? At least the T-90 did: T-90A from 1999
Realization of the turret was in the 1990´s, right, but a prototype testing with trials headed by I. I. Terekhin, M. I. Maresev, O.I. Alekseev, A. N. Popov by NIISt was published already 1977 (at a time when they used for RHA 42SM grade steel, with virtually identic physical properties to ww2 german tank armor) and very strongly argues that the thickness of RHA can be reduced 10% to 20% compared to cast armor at the very same level of resistence (compare: german ww2 sources state cast armor is inferior ca.15% in terms of aequivalent thickness):

"Calculations show, that the weight of a welded turret of a hardened rolled steel in comparison with a similar cast turret of armor of medium hardness with an equal protection level can be reduced by 6-8% with a turret weight of 6000- 7000 kg . This is achieved by reducing by 10-20% the thickness of the walls of the turret, as well as reducing the positive tolerance for parts from rolled products in comparison with casting.

With the same thickness rolled armor provides more then 10% increase of armor protection against sub caliber and ~4...5% against shaped charge projectiles.

Experimental types of rolled armor showed up to 30% increase of armor protection comparing to cast steel.
"

The "experimental" RHA armors were, of course, BTK-1 / BTK-1SH, later SK-2Sh and SK-3Sh and other higher hardness derivates which utilized the new electroslag remelting processes.

MH4UAstragon
Member
Posts: 23
Joined: 13 Feb 2018 19:32
Location: Eastern USA

Re: German discarding sabot rounds

Post by MH4UAstragon » 23 Feb 2018 22:40

So the War Thunder Maus turret being 220mm cast is effectively 85% of that thickness in RHA in the game then, going by that number you stated @critical mass?

That would be 187mm, which explains why even the likes of an IS-2 with only 208mm pen on its best round frontally punches through.

And I think the 30 degree numbers on the Pak/Kwk44 are the same ones as what’s ingame, but maybe the ingame 266/269mm values come from using the medium propellant charge in the modelling instead of the heavy propellant charge. The main gun velocity is also underperforming as a result of this.

By the way @critical mass, using that reported slope modifier for the 128, what was the gun’s actual pen against armor sloped back 60 degrees? The WT game displays 119mm on the APC and 120mm on the APCBC, and idk how correct those numbers are.

critical mass
Member
Posts: 678
Joined: 13 Jun 2017 14:53
Location: central Europe

Re: German discarding sabot rounds

Post by critical mass » 24 Feb 2018 00:52

As mentioned previously, I cannot comment on WT. While the 128mm KWK44 was laid out to be fired at 950m/s specified initial velocity, it was subsequently decided to use the same propellant cartridge as the 12.8cm PAK44 &, I believe, 12.8cm K80, with resulting loss of i.v. to 920-925m/s for rated MV. New gun velocity ("höchste V0") would be in average 950m/s.

revised penetration test data from feb. 1944 for 28.3kg 12.8cm APCBC (Pzgr43):
30° obliquity:
278mm RHA (unknown tensile strength) penetrated whole at 1090m/s velocity
248mm RHA (74.6-76.0kg/mm^2) penetrated whole at 950m/s velocity
201.7mm RHA (70-80kg/mm^2) penetrated whole at 835m/s velocity
45° obliquity:
150mm RHA (80-90kg/mm^2) penetrated whole at 885m/s velocity (=25% more velocity compared to 30°)

and for what´s worth the U.S. NavTechMisEur found internal documents at the Krupp works which were copied and are in NARA now. One of them contains a written short notice on 128mm Pzgr 43 (APCBC-HE) firing trials to determine the projectiles G(d) based upon 4 AKB 9524 charts, dated May 2nd, 1944:

all data for RHA at 30°

260mm (221BHN) complete perfotration at
974m/s (lower limit) to 1005m/s (upper limit)

240mm (221BHN) complete perfotration at
916m/s (lower limit) to 953m/s (upper limit)

220mm (221BHN) complete perfotration at
866m/s (lower limit) to 899m/s (upper limit)

200mm (221BHN) complete perfotration at
821m/s (lower limit) to 846m/s (upper limit)

180mm (221BHN) complete perfotration at
772m/s (lower limit) to 790m/s (upper limit)

160mm (several plates, 207BHN -234BHN) complete perforation at
735m/s (lower limit) to 738m/s (upper limit)

140mm (247.5BHN) complete perforation at
670m/s (lower limit) to 675m/s (upper limit)

User avatar
Mobius
Member
Posts: 595
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: German discarding sabot rounds

Post by Mobius » 24 Feb 2018 01:47

In the Lilienthal book the Germans conducted firing tests on 250mm thick Maginot line cast turrets.

MH4UAstragon
Member
Posts: 23
Joined: 13 Feb 2018 19:32
Location: Eastern USA

Re: German discarding sabot rounds

Post by MH4UAstragon » 24 Feb 2018 19:14

The initial velocity the game uses is 880m/s, so it’s not even the 925m/s used in reality nor the 950m/s used in testing.

User avatar
Mobius
Member
Posts: 595
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: German discarding sabot rounds

Post by Mobius » 25 Feb 2018 05:41

MH4UAstragon wrote:The initial velocity the game uses is 880m/s, so it’s not even the 925m/s used in reality nor the 950m/s used in testing.
There is a PaK44 firing table with 880 m/s so they must be using that. Of course there is another one with 920 m/s.

MH4UAstragon
Member
Posts: 23
Joined: 13 Feb 2018 19:32
Location: Eastern USA

Re: German discarding sabot rounds

Post by MH4UAstragon » 25 Feb 2018 07:56

Mobius wrote:
MH4UAstragon wrote:The initial velocity the game uses is 880m/s, so it’s not even the 925m/s used in reality nor the 950m/s used in testing.
There is a PaK44 firing table with 880 m/s so they must be using that. Of course there is another one with 920 m/s.
Are those velocities for different propellant charges I presume?

User avatar
Mobius
Member
Posts: 595
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: German discarding sabot rounds

Post by Mobius » 25 Feb 2018 14:11

MH4UAstragon wrote:
Mobius wrote:
MH4UAstragon wrote:The initial velocity the game uses is 880m/s, so it’s not even the 925m/s used in reality nor the 950m/s used in testing.
There is a PaK44 firing table with 880 m/s so they must be using that. Of course there is another one with 920 m/s.
Are those velocities for different propellant charges I presume?
I don't know. I also have a Technishche Daten for 12,8cm/L55 Pak 80 with a MV of 950 m/s. But there is no firing table to go with this.

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