What brass? It makes a huge difference when loading .308.
Check out www.accurateshooter.com forum. They have a lot of long range discussions using that bullet.
The left side of their website has a .308 dedicated link. I'm thinking Varget, VihtaVuori N150 and RE-15 would be good powder choices.
You really need Winchester or Lapua brass for long range ammo. The Winchester has the largest internal capacity, the Lapua can withstand the highest pressures.