Would offer to you to find marking of the Russian rifle of SKS in such variant OP SKS - Russian letters OP - Russian letters OP - mean a hunting commercial carbine SKS.
I can say simply, that to "beat" - to put to death from 100 meters a wild boar or within the limits of 100m. - 300m. - bobac it is not what that surprising . Think, that gross weight of booty on hunt can be varied from 150 kg. to 250 kg..
In relation to China is the Chinese production of SKS always worse and there is not original SKS, which was produced in Russia.
P.S.
7.62X39 (A cost of this cartridge is in Lugansk 0.3$ for one thing).
http://www.krechet.in.ua/catalog/category_264/producer_%CB%F3%E3%E0%ED%F1%EA%E8%E5/

You will be able these cartridges to shoot even from Chinese.
I give a producer to you:
Make attempt contact with the Lugansk cartridge factory (LCW)
PODKOPAEV SERGIY, Chief of Export Control Department
Tel.: +38(0642)93-32-09, +38(0642)71-88-28
Tel./fax: +38(0642)71-88-28, +38(0642)71-91-27
e-mail: lpzexport@mail.ru