I like Leupold mk5hd 3.6-18, Zeiss v6 or v8. The MPR is a slick rifle and if it were me, I would go with a lighter caliber like .308 in a 20" with a can on it. I, also am thinking about doing a similar setup and am seriously considering going with the XLR magnessium chassis. I am torn on whether to just get an MPR or use one of the tikka actions I have, add a carbon fiber barrel and XLR chassis. Costs are very similar but I personally like the tikka action better than the 700 clones. If you are thinking a long action magnum caliber for sure, I would eliminate the Tikka just based on magazine limitations.