I have a browning in 270 wsm and I didn' t have a mike but with a caliper I got .549 on a unfired new case ( right at the rim).554 on a fired case and .553 on a resized case from my RCBS die.
Have never had a problem with chambering and have problely shot around 200 reloads.
Are you screwing the die all the way down till it touches the shell holder?