Originally Posted by liltank
I disagree. I read an article where they compared short barrels verses standard length barrels. The short barrel rifles were just as effective to 500 and 600 yards as a standard length barrel. I have played with my own 18" barreled .308 and it shoots just as well as my long barreled .308 (28"). There is a bit of a performance gain with the longer barrel giving me more velocity obviously, but both shoot equally well. .5 MOA is standard with both using 175SMK's and 178 Hornady BTHP's. The 18" is a 1:10 and the 28" is a 1:12.
Bolding mine. There's your answer. Unless I misread the OP we're talking about building a dedicated "Long range" gun, not one simply suited for short to medium ranges.
If 600 yds is the max, then hell I'd save a ton of money and just buy something off of the rack and do a good free float, pillar bed, and glass it all in.