My BCM stainless barrel will run right along my buddies Rainier Supermatch barrels. I can routinely get .75 inch groups with 77 and 69 grain match loads. Anything much over 1 inch with quality match ammo is definitely me messing up. I've shot a few .5 inch groups, but it's average is probably around .8 to .9 inches at 100 yards.
It also shoots decent 55 grain ball under 2 MOA. I actually use 55 grain ball in my BCM SPR out to 600 yards regularly.
Like others have said there are a good number of high quality match AR barrels. If I was going for the best shooting rifle I could build, Id look at one of the barrel manufacturers like Kreiger, Bartlein, WOA, Doiglas, etc... but the BCM will shoot well.