Lead will build up in the bore over time with cast bullets unless you fire a few jacketed bullets now and then. That's the easiest way to clean out the bore. I had neglected my .45ACP barrel for a while, not bothering to do that or check for leading. It was unusually inaccurate the other day and when I got home and took it apart and inspected the bore, there were huge strips of lead in there. I scrubbed it all out in about 45 minutes with a brush, bore cleaner, and some vinegar (weak acid, reacts to form lead acetate). I thought about the Chore Boy thing, but didn't try it. I thought it might be a little too abrasive. I don't worry about vinegar. Now, don't to tossing muratic down your barrel, but vinegar ain't gonna hurt stainless steel, though it will NOT be good for bluing. I wouldn't use it on a blued gun. Be sure and clean it out, though, after the lead is gone.
After a range session, fire a few jacketed bullets. You won't have a normal lead problem if you do so. If it's leading up after a few rounds, you ain't doing something right with the bullet casting or are pushing them too hard.