Check out this link:
You'll need something to hold the bolt lugs against the receiver and use 300 grit if the lugs are pretty smooth; 400 if they're rough. Lube and clean out often.
Your headspace will open up a couple thousandths of an inch but with most bottleneck cartridges that's not going to matter if you full-length size fired cases and don't set their shoulder back. Belted cases are different; the barrel may need to be set back one turn then rechambered and if this is done it's a good idea to square the receiver front with the tenon thread axis so the barrel shoulder contacts evenly all the way around.
Lapping bolt lugs to full contact should be done along with squaring up the bolt face with the chamber (not bolt) axis. Otherwise, the impact of the fired case head against the bolt won't be even all the way around. The case head has to impact the bolt face such that forces are transferred evenly to all lugs so the barreled action doesn't whip differently with each shot. Lapping the lugs and squaring the bolt face is the only way I know of to do this.