I always thought that the Chinese steel core. copper washed shot better in my SKSs than any of the european ammo including the brass case lead core Yugo which came in 2nd. I imagine that there are more than a few cases of it rat holed away.
We had a SKS side match here last week. Offhand at 50Y, using a small 6" black bull NRA target. Although I have a few nice ones (SKSs), I elected to shoot a VN Chinese built Bring Back that looks like it had laid years in the jungle! I mean really ugly as in VERY rough wood & big rust pits every where. Inside though it was fine. Used the same ammo that you are talking about & won the match easily.
I have great respect for Mr. Simonov's rifle, having been on the receiving end of it. By the way, that is the same ammo that the VC were using. We captured & burned a lot of it.