I'd definitely go 1/10 twist for the heavies. Also for the 215 Berger, I'd throat for about 3.10" oal. That leaves abour .315" of bearing surface in the case neck, or just about to the neck/shoulder juncture.
Yes I made 2600 fps with 215s, in a 26" bbl, with RL17, moly, and a 3.10" oal.
215gr Berger Hybrid in the 308Win
I had a small number of bullets and didn't get past the 100 yard line in my limited test.
But, I've had good results with the following in a 1/12 20.5" 308, all shot out to past 1000 yards, even some crazy plinking out to a mile+,
225 Hdy BTHP.
All the above I moly'd, loaded to 2.9-3.1" oal in Win brass, and charged with 48-50 gr of RL17. Velocities ranged from 2500-2620 fps.
I'm only using the 1/12 barrel as it is the factory tube, 1/10 would be mt choice if going custom.