Is it as myth that once you are sighted in for hunting that you should not clean the barrell because it affect the point of impact?

Also can you recomend some cleaners for the barrel?

Thanks for the help guys, and oh ya if it matters the rifle I am sighting in is a 300wsm Browning A-bolt. I was planning on sightin in at about 1-1/2" high at 100 yards that should keep just a little low at 300 but I will have to check that before I attempt it in the field.