BO chamber neck is 0.335 max. I check all rnds for neck greater than 0.330, pull anything over sized. Get an outside neck turning tool, Elec drill with large chuck, put base in chuck and hold the turn tool - goes fast. I strive for 0.011-0.012 neck wall thickness and outside turning will uniform wall thickness - inside reaming doesn't. I can turn 100 or so before I get tired and it only is done once per case.