As far as rebarrel a Savage to a Grendel Cliffy on here would be a good person to talk to. I know he has done that a time or two.
The Creedmoor will always be a faster round than the Grendel larger case burning more powder. On pressure difference, SAAMI spec for max average pressure 52000psi for the Grendel and 62000psi for the Creedmoor Source
Max loads for the Gendel burn about 30 gr of powder wile the Creedmoor burns over 40 grains so about 25% less powder. There is data out there for loads with the Grendel running in the 55000 to 60000psi and getting 2700 or a bit more from the 123gr bullet while burning about 32 grains of some powders.
The Grendel has trajectory that pretty much matches the 308 with 168 or 175 bullets and is supersonic past 1K so it can get out there if wanted.
I have an AR in the Grendel that shoots good and works well on hogs and yotes but just want a boltaction in it for a light weight hunting rifle that will reach out as far or further than I want to for deer, but can be fun on targets on out there. The light recoil also makes for fun shooting.
Mostly about ARs which are the only commercial guns chambered in the Grendel, but an interesting read.http://www.rifleshootermag.com/uncategorized/6-5-grendel-evolution/