I have had some success using Kroil to remove leading. I soak a loose fitting patch and liberally wet the bore and let it sit an hour or so, and then run a dry tight fitting patch through. Repeating if it unsuccessful at first. If you are successful, you will get striations of lead coming out with the patch. Kroil is a creeping lubricant not a solvent. It can get into microscopic crevaces and break the bond between the lead and metal bore of your firearm. It doesn't always work well for me, but when it does, it is quite impressive. I like Sweet's 7.62 copper solvent for removing copper fouling.