Here are the best results AFTER taking the steps I listed previously:
Federal Fusion 95gr, less than an inch:
Rem Core-Lokt 100gr, less than an inch:
Two separate groups with Fed Blue Box 100gr, well under an inch:
Not all ammo choices showed improvement, though. Hornady 100gr Interlocks spread out to 2+ inches, and Federal Premium with 95gr NBTs were 1 5/8" at the best.
Still, I'm VERY happy with the improvement shown with really minimum effort - dropping a bread wrapper tag into the recoil lug recess to eliminate play in the action, and using another one to elevate and free-float the barrel. Oh, and REALLY tightening the stock screws, of course.
I'll be interested to see if the changes become permanent once I sand out the barrel channel and glass bed the recoil lug. Working on the barrel channel will also give me a chance to reduce any tightness on one side of the barrel from the sloppy factory fit of the stock.
Thanks, all!!!