with a bolt action (or any open bore action), the rifle is stabilized in a rest, the bolt removed, then i'll peer down the bore at a mark 50 yards away, visually centering the mark in the bore. look up and do the same with the scope, adjusting the reticle to coincide with the mark. that's it, and i know i'm at least on paper when i visit the range. any closed action rifles will require the use of a laser bore sighter, but bolt actions are too easy to living room set up before hitting the range.