Keep all smooth or rifled barrels in a perfect condition, simply and quickly, just shooting 2 successive pellets.
Shootin causes a build-up of pressure, which expands the pellet . This means that every part of the barrel (even the rifling) is thoroughly cleaned and polished.
From time to time, for a thorough cleaning, soak 2 pellets in a gun oil, and shoot these one after one. Remove then the oil from the barrel, shooting dry pellets, until these come out from the barrel white and clean.