Everybody’s got their methods. So I’ll tell you mine. After I do a build the first thing I do is use a cartridge style bore scope, this gets them fairly close, I’ll remove it, spin it and reinsert it three times just to verify it’s on point and that the laser hasn’t gone stupid. Then it’s off to the range, fire, adjust, rinse and repeat as needed. But I cheat on this part. And this might not be for you, I have a hydraulic buffer tube and a recoil reducing muzzle brake that I use on my rifles while sighting in, I use a lead sled that I mount the gun to and I run subs one at a time since most won’t cycle the gun. So basically I strap the gun down where it can’t move, reduce as much “felt recoil” as possible. On average it’ll be dead set by the fifth shot. Then I switch out the buffer and brake and test fire with 5.56 from a standard position.