My 6.5 experience is limited to .260 Rem. Having said that, it was done with a 28-inch Shilen 8-twist bull barrel, so these comments are likely relevant to bflee's query.
120 AMAX did well. 140 AMAX did well. 139 Lapua did better than anything else.
My experience has been really good using both Varget and N150. Nearly all of the shooting was done in f-class midrange - 300 to 600 yards. Whenever something other than an x is shot, it's the shooter's (my) fault.
The 139-140 bullets tend to really shine at distances past 4-500 yards.
Not to be a wise guy, but if I were to load 6.5 CMs, I would look at the recipe on the box. I have heard it is hard to beat. The guys at Hornady, in concert with DeMille, put a lot of effort in to getting that recipe right.


Good luck.

JS