You never achieve ultimate precision with factory ammo. If I could walk to the store and grab a hundred 6BR loads that shot like a custom re-load, I'd definitely do that instead of wasting my time at the relaoding bench. Optimal powder types, powder loads, seating depth, bullet styles/weights, primers, run-out, neck tension, and brass consistency are all variables that are minimized or standardized with proper reloading.
Even so called "Match ammo" can be mediocre at best. The ammo must be matched and tailored to the individual gun.
The problem is... to get to the point where you can manage all those variables, you are into thousands of dollars and alot of practice.