"Tank-hunters" of the first party have participated the Battle for Moscow in 1941-1942. In particular, there were 10 T-34-57 in the 21st Tank Brigade, that was formed in Vladimir. On October 14, the brigade has been deployed at Demidov rail station and a day later it was ordered to advance on Turchinovo-Pushkino-Troyanovo and make a flank strike on German troops deployed near Kalinin. Starshiy politruk (Soviet rank) E.Gmurya drove his tank along the Volokolamsk highway had met with big column of German trucks. His tank has destroyed the whole column of 3-km length. After that, tank rushed in German aerodrome and has destroyed a heavy bomber. After that, tank was knocked out by German artillery, two crewmembers were killed. Politruk Gmyrya and sergeant Ishenko escaped and rejoined Red Army. After 4 days, 21st Tank Brigade destroyed 3 German staffs, about 1,000 soldiers, 34 tanks, 210 trucks and 31 guns. Brigade has lost its commander - Hero of the Soviet Union, major Lukin and commander of the 1st battalion Hero of the Soviet Union captain Agibalov. By November 25, all "tank-hunters" of the 21st Tank Brigade were lost. Another photo of the Lukin's tank. [SIZE=-2](M.Baryatinsky)[/SIZE] I could find a mention about 8 T-34-57s being added to the 8th Tank Brigade on October 19, 1941. All I could find about those tanks was mention of lack of ammunition. Unfortunately, I was unable to trace their further fate. The new T-34-57 "tank-hunters" had appeared on the frontline in August 1943.They've been attached to "special tank company 100". That company had three T-34-57s in its first platoon from August 15 to September 5, 1943. Unfortunately, "tank-hunters" were unlucky. During all those weeks, the company would meet German tanks only once, but in that time the 1st platoon was in reserve and didn't engage the battle. So, "tank-hunters" were unable to prove their efficiency against German armours. Nevertheless, commander of that company captain Volosatov and delegate of the GABTU colonel Zaitzev, have praised T-34-57 very high after shot practice on knocked out German tanks and captured pillboxes and bunkers. The main drawback of the ZIS-4 and the ZIS-4M tank gun was very low quality of HE projectiles: they either exploded partially or didn't explode at all. During 1943, the Factory #92 had manufactured 172 ZIS-4M guns, then it mass production was cancelled in favour of 85 mm guns. Although, according to factory's report on 1944, it had manufactured additional 19 ZIS-4Ms. Perhaps, for repair some existing "tank-hunters". The Russian Battlefield - T-34 Tank-Hunter
I also understand there were issues with the gun's accuracy. The barrel tended to have too much droop and vibration causing a pretty large grouping of shot at even relatively short ranges.
Ceraphix, besides the technical problems T.A.Gardner mentioned, there is also the fact that Soviet tanks were not to be specialised tank-killers, they needed a decent HE capability, and the 57mm shell was too small for the purpose. So good as the 57mm gun was, it was difficult to manufacture in large numbers, needed development, and the explosive round was considered small for general pupose work. Kriegfilms, 2" is not exactly thin skinned if you take into consideration the very oblique sloped armour.