If you think about it, 6 to 12 inch groups at 100 yards does not compute lol.
People think about the SKS today the same way people thought about the Carcano in the 1950s through the 1970s. I will concede that with proper ammo, the Carcano is head and shoulders more accurate than the SKS, however this is an apples and orange comparison.
The 59/66 is the most accurate SKS I have tried. I could get 3.5" X 5 shot groups with Cz surplus ammo @ 100 yards benched. Someone who was a better shot might have been able to shrink the groups a bit (with modern PP or SB ammo?).
The best I could do with my Bell refurb SKS (Russian) was a 10 shot group of 4" @ 100 yards from the prone position again with Cz surplus ammunition. That rifle had a PLA phenolic stock on it at the time.