Thanks for the input folks. The only thing I'm concerned with is powder availability, pretty tough to find rl16/retumbo/h1000. However I think those same powders are used in the other mags as well. Brass seems available, if a bit tough to find. Haven't looked into projectiles; I kind of assumed 200gr+ bullets would be available.
The PRC seemed like it was a better choice than 300WM since it isn't belted. More brass life. This may be an overstated issue.
Haven't looked seriously into any of the 7mm cartridges besides 28 nosler, but if they're better than 300prc I'll have to take a look. 28 nosler brass (nosler, Hornady) is like 3$ each. Double the cost of Lapua 300 PRC. shorter barrel life, not much ballistic difference at sub 1K. Didn't seem worth it.