Jeremy,Great setup. Love the cartridge and scope (make mine MOA though). I don't have any first hand knowledge of the RPR but from the few reviews I have read, it appears to be a shooter right out of the box.
I'm working on another model chassis rifle a friend. He has the Savage MDT LSS-XL and I've been trying for a week or so to find an accurate LR hunting load using the 200gn ELD-X. Thought I'd found a decent load (low ES/SD) but groups hovered around an inch. Had ELD's set at .010" off and using IMR4831/WLRM primers. One session it would print .5", the next 1.0" and so no.
Went on line today to find the torque specs for the action bolts. Everything I found said 60-65 in/lbs and that's what his was set at. With nothing really to loose I backed it off (adjusted AccuTrigger to 2lb while out) and started at 40 in/lbs for the back and then front action screw. Stepped out back and after the 3rd shot I knew I'd found the answer.
View attachment 301447
The group on the left was after cleaning the barrel but typical of what I've seen all week. Group on the right is after re-torqueing. Hopefully yours will print one-holers from the git-go. Good luck and let us know how it does.
Load is using Peterson .300WinMag "Long" and 71.5gn.
I know in the OP you said you had tried torque changes but I posted this in another thread on here and thought about your situation. I have another rifle that I acquired from the same fellow, it's a Savage 340 in .222 Rem. He said it would only shoot about 1.5" groups at 100yds and on it's maiden voyage at my range, sure enough he was truthful. After some tinkering and reading I found out that the rifle is sensitive to the adjustment of the barrel band which is attached to the forward action screw. With a few adjustments and after a thorough cleaning it prints .5" groups with Hornady factory 50gn V-Max.
I should probably re-adjust all my rifles periodically and write it down in my shooting journal.