0 is the best. It means a fairly new/properly set up rifle.

My LB sniper is presently on a #2 bolt head. I have a few 3s squared away in case the day ever comes, and after that I guess I'll be either building one up, or else reworking a Cno7 head.
I only go through maybe 300-400 rounds a year, so it should be a while before I have to worry about such things.
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