What is this LR pistol going to be used for? If strictly LR matches or hunting off a bench or even prone then I'd not even consider anything other than an undesignated Savage Target action and build from there. I just finished one on the Target action with a rear grip 7fingers stock in 6XC and also an XP100 converted to rear grip with another 7fingers stock in 260 with a McGowen Rem-Age barrel setup.
I already had two XP100 pistols to work with that we shot as mid grips for our local 1000 yard steel plate matches and wanted to see how one would work set up as rear grip. It needed a new barrel so we set it up as a rear grip. Now that I've had more time to work with my Savage Target LR pistol in 6XC it's hard to even take time to work with the XP100 although it does shoot fantastic but being lighter it does tend to jump slightly more than the heavier Savage so we can see hits/misses easier.
If anyone asks me after seeing all of our LR pistols which I'd go with if doing another one, order a Savage Target Action with one of the many pre-chambered barrels, add a 30moa mount and a 7fingers rear grip stock with a good scope and you'll have the rifle shooters looking for ways to increase their scores at those extended distance matches.