While not perfect, my ES has been reduced dramatically by careful attention to the bullet grip and the interior finish of the necks before seating. Here are the last shots fired over the chrono from various rifles
338RUM 225 gr TTSX 94 gr RL25 FED215M
6.5 rem mag 125 NPT 58.5 RL22 FED215M
280AI 160 AB 60 gr RL25 FED215M
375 Ruger 260 AB 84.5 gr RL17 FED215M
30-06 200 gr AB 60 gr RL22 FED215M
Very seldom do I get an ES of 50 and that will be because of 1 shot that is out of the group. These are all seated off the lands. The AB's around .020" and the TTSX at .050".
These have .003" bullet grip and the inside of the necks cleaned and polished with Scotchbrite
and lubed with mica
along with seating with Competition Seaters and seating variances of .002" or less, sorting bullets by bearing length and measuring each powder charge, it works for me.