maybe weigh primers and bullets before brass weight? I too went down the road to eliminate as many variables as possible from the get go. Then if I do that the only thing I can do is become a better shooter. There are some that say get a decent load(1MOA or better) and shoot more to get better. Then I believe in getting the absolute best ammo first, eliminating variables you can control with the tools you have, then learn to shoot with those.
I uniformed primer pockets, deburr flash holes, sort by neck wall thickness, sort by neck wall runout, trim to same length and since doing these steps I have went to sub 0.25" groups@100 yds. Previously was around 3/4 MOA. Nothing else changed