You guys are completely overthinking this...
I've shot probably well over 100K rounds of .45ACP 200gr SWC through several of my .45's, my typical load is 3.8grs of hodgdon clays, a very mild load, but totally adequate for punching holes in paper and making steel go "ding". When it comes to firearms, fouling is a fact of life, this is why they make "gun cleaning kits", and it's also why over 100 years ago they started putting jackets on bullets for military use (the lowered maintenance made up for the higher cost of the ammo).
The best thing to do, if you have a stainless barrel (non blued) is to take your barrel out, put it in a cup, and fill the cup with 50/50 hydrogen peroxide and white vinegar. This will eat the lead out of your barrel. However it will also generally strip bluing. After letting it soak for an hour or so, use a rifle brush, just like everyone said, and repeat the process if there's still lead in there.
The real trick to this, clean the barrel out with brake cleaner (remove all the oil/wax) first, and then let the chems do their job. Oil the barrel like normal afterwards.