The key is the barrel, don't buy a reg AA 6.5 barrel made by Shaw if you want accuracy at 500yds. Lothars barrels are better or the 264LBC is a better chamber too same brass and dies as a Grendel but the throat is a more accurate 1.5 degree design. Black Hills 264LBC factory 123gr SMK ammo will shoot under 1/2MOA out of the box if the shooter can drive the rifle, lightweight ARs with larger calibers need more front end control since the rifle doesn't weigh enough to keep the front end down while the bullet is still in the bore.
5.56, 6.8, 264LBC, SIX5.
The Nextgen of 308 rifles