Soviet UBR 354 S Special APBC for the ZIS-3

[Miles Krogfus]

When the ZIS-3 was introduced in 1942, the new APBC projectile BR 350 A also had begun production, having a normal APBC round with 1080 grams of 9/7 propellant giving a 662 m/s muzzle velocity, and a "Special" round UBR 354 S using the BR 350 A APBC and 1400 grams of 9/7 propellant with a 745 m/s mv. Its mm penetration with a DeMarre 2450 K factor and the following 0 and 30 degrees deflection at these ranges and velocities:
100 meters 735 m/s 90/73 mm, 500 meters 696 m/s 82/67 mm, 1000 meters 646 m/s 74/60 mm, 1500 meters 596 m/s 66/54 mm, 2000 meters 549 m/s 59/48 mm. However when the Summer 1942 Eastern Front campaign went on and no new really thick armored Panzer appeared, it was decided to stop production of this special round.

[Mobius]

I've never heard of this round before. Are the penetration numbers for Soviet, German or British Ordnance Board criteria and test armor plate?

British Ordnance Board firing test curves: critical velocity (CV = the 3 highest partial perforations with no projectile completely through, or 50% chance

Plus the m/s loss between 500m distance marks cannot be accounted for by any real ballistics.
0-500m = -49m/s
500m-1000m = -50 m/s
1000-1500m = -50 m/s
1500m-2000m = -47 m/s

[Miles Krogfus]

The velocities and mm of plate penetrated are taken from the official Soviet firing table of this projectile with its larger 1400 grams propellant that I mention. The containers holding these rounds were clearly marked SPECIAL . . .

[Mobius]

Something like this may be in play.
http://forum.axishistory.com/viewtopic. ... 7&t=215996

This has some examples of very good firing tables.
http://digitalcommons.unl.edu/cgi/viewc ... odmilintel

[Mobius]

I take it back. That PDF had a shell with rather strange ballistics. It was the O-350 HE shell. Compared to the BR-350 shell it slows down pretty fast after firing. The BR-350 catches up around 700m. But somehow the O-350 gets a second wind and catches up again at 2500m and passes. I post here excerpts from the firing table and a velocity graph.
I've never seen this type of ballistic behavior before. I checked US 75mm AP vs HE shells and 76mm AP vs HE shells and they do not do something similar.
Puzzling.

[Peasant]

Okay, sorry to resurrect an old thread but I found physical evidence that this unusual shell actually existed. A user on russian web site was selling this empty case. The writings says
"UBR-354C
FOR ALL 76MM GUNS 45(?) - 50 (something)
FOR FIRING AT TANKS ONLY"

The markings on the round shown at http://michaelhiske.de are in russian, which confirms that this is not a german manufactured round for the 7.62cm Pak 39 gun. What is believe to be the year of manufacture is '41.

I have a theory that this round was a from a small series made for soviet 76mm F-22/F-22 USV divisional guns in 1941 to counter possible appearance of the new german tanks with 100mm of armour the soviet intelligence was warning about at the time. But as it became clear that this was not the case the production was quickly shut down and resources diverted to more pressing matters.

Edit: I've checked the "UBR-354C" code in GRAU database and couldn't find it. This round was never standardized.

I did the math, that Miles seems to have done before me, to verify his results:



Source: http://michaelhiske.de/Wehrmacht/Heer/H ... 16_02c.HTM

Interpolated external ballistics curve shows relatively normal flight characteristics, where the lower the current velocity is, the lower is the rate at which its loosing velocity. Also it seems to be more aerodynamic than the BR-350B shell:

[Peasant]

From: "D435-2b Handbuch.Die Munition der Beutegeschutze und Werfer (Griechenland, Jugoslawien, Polen, Russland)"