What tools are you using? I have found a few things when I was dealing with minimal tooling. After getting the headspace where I want it(usually against the go gauge for me). I index mark the action/lug and the barrel to the best of my ability. Using the .050 linear movement per rotation constant, I figure that 45* of rotation has linear movement of I smidgen over .006. So I would back my barrel off of the gauge a fraction of that 1/8th turn and smack the nut wrench with a rubber mallet. And compare the match marks again. I repeat that process and use your gauge to verify. Most factory ammo is going to prefer you to be close to the middle of the tolerance, possibly more to the large side.

Currently a barrel vise and an action wrench makes everything much more precise.