I'm not really sure that the SKS even rises to the level of "plinker." I've got one of the ChiCom versions, one that takes AK mags. It's fun to blaze through 30-round mags with it, but when you're plinking, you sort of like to hit something once in a while. With my ChiCom SKS, if you want to hit something, you'd best use the rifle as a club.
I find it amazing that people sell scope mounts for these things. That really falls into the "you can't polish a turd" category.
I know plenty of people who get 2 MOA out of unmoded SKS's. Thats perfectly respectable for a battle rifle, and better than the SMLE no. 4 in sniper packaging. I'd say if you can get it to group under 4 inches at a hundred yards, your golden for plinkin'.