German fin stabilized HEAT ammunition

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Tenkist
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German fin stabilized HEAT ammunition

Post by Tenkist » 20 Jan 2018 14:57

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Pictures comes from WT forum, posted by Whelmy

https://forum.warthunder.com/index.php? ... velopment/

I am looking for other information about this ammunition. It's a bit weird that there is so little information on this topic. This document shows that fin stabilized 15cm Hl was in production.
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.
Posted by critical mass

~40mm difference in penetration value at 30°

critical mass
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Re: German fin stabilized HEAT ammunition

Post by critical mass » 20 Jan 2018 17:25

"HL Ausf. C mit Klappleitwerk" means HEAT-FS. Klappleitwerk are sping loaded, collapsed fins, which deploy once the projectile has left the muzzle. The induced spin by the barrel rifling was reduced in some designs by a driving band mounted on a ball bearing, thus, the bands rotate freely with only minimal spin induced on the projectile.
Last edited by critical mass on 20 Jan 2018 18:08, edited 1 time in total.

Yoozername
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Re: German fin stabilized HEAT ammunition

Post by Yoozername » 20 Jan 2018 18:06

It is an interesting but considering the date, February 9, 1945, it seems to be in a bubble of denial.

They never mention using copper for the HEAT rounds. I assume they want more penetration but want to stick with brass liners?

It seems the discarding sabot for the 10,5 cm using the 7,5 cm pzgr 39 projectile was produced in quantity, but never fielded? This would not really give penetration much more than a regular KWK40?

critical mass
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Re: German fin stabilized HEAT ammunition

Post by critical mass » 21 Jan 2018 22:04

They experimentally aquired in knowledge of the effects of different liner materials (incl. copper), liner geometry, effect of distance , effect of spin rate on HEAT warheads. The document proposed here shows how much they were willing to buy into the HEAT development in countering the anticipated 250mm armored target threat. HEAT FS had the advantage of allowing the utilization of existing guns and greatly expanded the amount of penetration.

Full calibre 7.5cm Pzgr39 had more accuracy than HEAT FS but only at short range (for the KWK42) had similar penetration. Downrange, however, the HEAT-FS penetration was superior, irregardless of whetehr it was fired by PAK40/KWK40 or KWK42. HEAT was also less affected by obliquity effects than -TS projectiles, which might be worth mentioning.
Similarely, the 10.5cm/7.5cm Pzgr 39 Ts sub calibre discarding sabot transferred the 10.5cm leFH into PAK40 level anti tank capabilities, which was marginal. HEAT-FS allowed it to reach PAK43 levels of performance.
Discarding sabot for the 10.5cm which often was fitted with muzzle break was problematic. HEAT-FS on the other hand, didn´t had these issues.

However, the document gives some uselful numbers:

7.5cm HEAT-FS: 140mm at 30° (in developement)
10cm HEAT-FS: 200mm at 30°(final development)
12.8cm HEAT-FS: 220mm at 30° (projected)
15cm HEAT with Minenleitwerk (HEAT with rigid fins): 240-260mm RHA @ 30° (at hand)

seppw
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Re: German fin stabilized HEAT ammunition

Post by seppw » 21 Jan 2018 23:07

critical mass wrote:They experimentally aquired in knowledge of the effects of different liner materials (incl. copper), liner geometry, effect of distance , effect of spin rate on HEAT warheads. The document proposed here shows how much they were willing to buy into the HEAT development in countering the anticipated 250mm armored target threat. HEAT FS had the advantage of allowing the utilization of existing guns and greatly expanded the amount of penetration.

Full calibre 7.5cm Pzgr39 had more accuracy than HEAT FS but only at short range (for the KWK42) had similar penetration. Downrange, however, the HEAT-FS penetration was superior, irregardless of whetehr it was fired by PAK40/KWK40 or KWK42. HEAT was also less affected by obliquity effects than -TS projectiles, which might be worth mentioning.
Similarely, the 10.5cm/7.5cm Pzgr 39 Ts sub calibre discarding sabot transferred the 10.5cm leFH into PAK40 level anti tank capabilities, which was marginal. HEAT-FS allowed it to reach PAK43 levels of performance.
Discarding sabot for the 10.5cm which often was fitted with muzzle break was problematic. HEAT-FS on the other hand, didn´t had these issues.

However, the document gives some uselful numbers:

7.5cm HEAT-FS: 140mm at 30° (in developement)
10cm HEAT-FS: 200mm at 30°(final development)
12.8cm HEAT-FS: 220mm at 30° (projected)
15cm HEAT with Minenleitwerk (HEAT with rigid fins): 240-260mm RHA @ 30° (at hand)
I guess the problem with discarding sabot was the sabot hitting the muzzle break?
"HEAT-FS on the other hand, didn´t had these issues."
You are German, because it should say "didn't have these issues". :p
"10cm HEAT-FS: 200mm at 30°(final development)"
Very interesting, thank you. Do you have any info on the ballistics of this shell? Shell travel times and 50% zones?

Yoozername
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Re: German fin stabilized HEAT ammunition

Post by Yoozername » 22 Jan 2018 00:31

It is, BTW, muzzle-brake. It is acting as a braking device, not breaking something.

Tenkist
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Re: German fin stabilized HEAT ammunition

Post by Tenkist » 22 Jan 2018 14:30

What do you think? Are 15cm HL/Ausf. C mit Klappleitwerk and mit Minenleitwerk the same projectile differing in type of fins?
This would mean that for obvious reasons only the work on rigid fins was continued.

I think that this ammunition would give the chance to defeat heavily sloped soviet armor (T-54, IS-3), of course if war would last longer.

critical mass
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Re: German fin stabilized HEAT ammunition

Post by critical mass » 22 Jan 2018 16:23

I have not found a drawing for KLW of HL Ausf. A/C round but for the oversized, fin stabilized Mineprojectiles (HE-FS) and attached to this memo. The mechanism of the spring loaded fins is virtually identic to and also is designated as "Klappleitwerk".

Apparently, only screwed on rigid fins were made for 15cm (Minenleitwerk). Though the first report (dated 1944) gave a penetration of 210mm/30°, this january 1945 memo attributes this projectile a penetration of 245mm @ 30°, almost identic to the 15cm HL m. KLW.

There were a lot of HEAT trials during 1944, and I haven´t seen most of the reports yet. However, going by the data for the 66mm rifle grenade trials, an IS3 could also be perforated -in theory- by 66mm anti tank rifle grenades. And by 128mm Pzgr43, even the KWK43 may be marginally effective (f.e. turret and side hits), when firing a good quality lot of projectiles.

There is a real problem with changing priorities in the documents of this timeframe. You find that X was approved for mass production at a given date and another document from just two weeks later counter mandate that order and call for a different design to be manufactured.

7.5cm HL Aus. C m. Klappleitwerk (75mm fin stabilized HEAT-FS for PAK40) by january 1945 passed development, 0-series production (pre-series) and was about to be service introduced. But it would require more documents from a later date to answer what happened to the ammunition produced and whetehr or not it was passed on to units. Such a projectile had the performance to be effective against the heaviest tanks encountered, f.e. IS-2 heavy tanks (even mod. 1944 glacis).
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