SKS's seem luck of the draw.
I have a heavily used one from wholesale sports. Dead reliable always goes bang but super loose fitting parts and 6"-8" groups at 100 yards, good for 3 or 4 out of 5 shots into a 8 inch gong at 100 yards. Hot or cold has no noticeable effect on groups. And ive put 500 rounds through this thing in a few hours before so it go really warm.
I have a looks brand new super tight fitting one I got from corwin arms, shoots 3" groups at 100, put 55 rounds in a row into a 8" gong at 100 yards once just to see if I could, probably could of kept going and hitting but got tired of holding the rifle(was shooting offhand). This one seems to tighten up a little when warm, shooting from a rest I once shot a less than 2" group, twice in a row, when it was hot enough to evaporate water off the barrel(it was raining)