OK--answers as best as I can make out:
I've stuck some 6.5 x 284 norma cases in a 308 mag and near as I can tell that's not an issue--but that doesn't necessarily mean they'll feed well I guess. The SAAMI spec for COL is a smidgen above a the typical 308 design but shouldn't be an issue.
What I'm pretty sure
will be an issue is relatively far shoulder-forward case design and short neck--I know that's going force limitations on just how high a BC bullet design I'll be able to get held by the neck--and will also result in case capacity encroachment. I see it as being sort of analogous to a "super-sized" 6.8 spc.
Obviously extra care will be needed in developing loads.
I've been advised to use standard mass BCG--the rim face is the same as a 308's so I'm guessing a standard 308/AR10 BCG will do the job (?).
The barrel is being made 1:9 twist with rifle + 2" gas system, I plan on running bullets in the 140 to 160'ish grs range--not sure bigger bullets could work.