Well, I know the scope mounts and action screws are tight. I took them out and re-torqued with Blue Locktite and my Fat Wrench a little while ago.Dam if I know make sure everything is tight on the scope and mounts also check the action screws. Maybe try some different ammo. I know how frustrating this can be. Good luck let us know what it was when you figure it out. I have been eyeballing one of those little rifles In 7.62-39, just becuase it is cheap to shoot and I like to waste ammo.
I'll clean it, and go back out on Thursday to see if that helps. I'll try at 25 yds ... then 50 ... and then 100 yds. to see if it starts "Acting Up" anywhere along the way.
The scope is a New Redfield scope that I bought this past weekend, so I'm fairly certain it's not the scope ... unless I got a Dud.