Went through the same questions a month ago for a rebarreling project. Went with the 6mm Creedmoor just to have something different, plus I have a 6.5 Creedmoor. I found some brass at Midway if you're thinking of going that route. I haven't found a lot of load data for the 6mm Creedmoor. Most seem to be using H4350 around 42 grains. I wish is could find some other data for other powders, like Varget, etc. that are easier to come by. I only have a pound or so of H4350.
Haven't gotten the rifle back, but I am satisfied with the route I chose. I haven't decided on dies yet though.
