what turns the fouling white. That is salt concentration from your powder.... usually occurs after the bore has not been cleaned for a spell or been left out in the open air of your home, garage, auto... etc
I clean after every trip to the range or shooting. The ring is only a 1/4 " wide at the end of the barrel.
Best to keep your fouled MLs in a hard shell, poly-foam gun case that keeps it air-tight inside your home after range work
Have heard the opposite , my dads ithica was kept in a foam case with poly foam. When I took it out the other day the foam "fingers" had left what looked like fingerprints all over the gun. I keep my firearms in a gunsafe when stored. 8 out of 10 ppl I've asked state to never keep your guns stored in a case