Re: Factory ammo suggestions please....
IMHO, you will be best off simply trying a couple different premium shells. Your rifle may not like what other rifles like and vice versa. If It was me looking for a load I woud find one of the cheapest brands I could and get a 150 gr, 165 gr, and a 180 grain (in the ball park anyway). Find out which of these weights will shoot better. THen I would go to a couple different brand of premium cartidges in that approximate weight and do the same. Your 12 twist should stableize anyting less than 200 grain. You are better off with the long range stuff to try to get a higher BC for the weight so you want Boat tails. However, If your rifle shoots flat based bullets better than you will be better off just shooting what works in your rifle.
IMO the optimum weight for long range in a 308 is between 165 and 190 but that is just my opinion... I don't shoot the 308 anymore so I have no real first hand experience.
Good luck, Mark.
I used to re-load but now I "hand-load".
-- Well, at least I try