To add on to what thomae told ya, make sure when you take the action out of the stock - check for the simple stuff, not sitting properly in the recoil grove etc. When you put it back in the stock make sure you set it back against the recoil lug and bring the front action screw up snug. You can torque things if you like, seems like the front should be around 50 inlb and the read around 35 in/lb. It's important you do not bring the rear screw up tight before the front one is at least snug. It won't sit in the stock properly otherwise.. Just as an parting shot though with you symptoms I'd really suspect the scope mounting being the problem.

Ron