Use Dan Neberry's round robin method. It will even out a lot of teh variables. With my varmint rifles I have been know to shoot over 1K rounds with nothing more than pulling a bore sanke with a bit of Break Free through the bore. After a couple of hundred rounds. My rifles will shoot minute of bullet hole.
I usualy clean them realy well with a copper solovent once a month or so. Note I usualy shoot at least 200 rounds out of each of them every range trip.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.