Wow, can't believe I've made it to page 3 and not seen anyone recommend the Outer's Foul Out system. I've used the Foul Out III for years to clean leading from bores. Works electrochemically, kind of like reverse chrome plating. Not nearly as toxic as the mercury!! Not nearly as labor-intensive as most of these scrubbing techniques (though they are innovative). You just plug the bore, fill it with the provided chemical, drop the electrode in and walk away. Come back in 15/20 and pull the electrode out with most or all of the leading on it. Repeat only if necessary (isn't usually) then clean the remaining carbon out with your normal solvent. Works on copper too, using a different chemical.