UP, If you are committed to the Ascent, that is your choice. From that point, I'd give the nod to the .270 over the .308 for down range ballistics. I'd be pursuing the .277 bullet lineup for some of the top BC values and checking what the Ascent likes. A cursory glance shows the 140 and 150 gr Accubond as being close to .500.
Good luck
