I would run a brake or can on a 300 if I go that route. The 7 mag makes sense but the factory barrels are twisted for 175 and down it appears. I do have about 200 162 amax sitting around
Many 7RM factory twist rates are 9", but even a 9.5" will marginally stabilize the 180 ELD, 190 ATip, and 195 Berg at 7RM speeds. As a worst case you may lose a few percentage points on the BC value, but they'll shoot fine. Unless you're at sea level shooting in 0 F weather with a 9.5" twist, the reduction in BC will be minimal and possibly non-existent.
