Six to eight inches at fifty yards is too many inches. I would check every accessible screw, starting, like others mentioned, with scope mounts. Check the barrel channel also, to make sure no tension pushed the barrel.
How is the report with 7.62x39 from your rifle?
I am thinking about one, was looking at Ruger, then CZ is coming up with the 600 line, I think I like the Ergo, which can be pre-ordered now in Canada. There are still some brand new 527 carbines available here... They look better, but my best iron sights days are behind me and I believe the overall usability of a synthetic stocked rifle, easy to mount a scope on with a good shooting position, would satisfy me more than good looking wood and blue. It's just that I love wood and blue! Hope I won't regret not having bought one when it was still available.