I used to have a leading problem in my 686. Couldn't resist loading "HOT" with lead bullets. To clean out the lead buildup I used this:
Lead Remover
IIRC, it used to be available under the name "Wipe Away" and I was able to buy it in actual patches. A couple of strokes through the bore and the lead would come out, sometimes in long threads where it was released from the rifling.
Also was great for cleaning the powder burns off the front of the cylinder. They did warn against using it on the bluing though.