It would depend on the range. I had a .308 that would shoot in the .1's consistently with several screamer groups thrown in at 100yds. I shot plain old Sierra 125gr SPT's in it with H4895. Out to 300yds it was amazing. Past that the wind would screw with it pretty good. It had a Hart 1.25" straight barrel on it. I built the gun myself.
The smallest group I've shot at mid ranges was with my .30-8mm last year. It was a 3 shot .96" group at 550yds. It's a Rem. action with a Sendero contour Bartlein barrel. I built this one myself also.
The best long range group was with my .308 Baer that Bruce Baer built for me 20+ years ago. A 5 shot group just under 4" @ 1000yds. It's a 1.25" straight Hart barrel 30" long.