I've mentioned this tip a few times but if you take a "copper" charbroil pot scrubber (don't buy the stainless or bronze because it will damage your barrel) then cut some off, and wrap it around a brush once or twice so it's only a snug fit in the bore, it will scrape all the lead out of the barrel quickly, and it doesn't take much effort. Only go from breach to muzzle.
Then clean as you would otherwise.
I learned this from a old friend for pistol shooting with lead bullets and it's way faster than using the chemicals or current products. Could probably follow up with chemicals but I didn't feel the need for my application back then.
BTW I'd be wary of using anything that attracts moisture inside a barrel, especially in humid areas.
Example - I won a new soft case in a raffle once, and left my FX Royale in it for a few weeks, and the steel got pretty much ruined from excessive rust because the foam inside the case, as I found out from researching about it, "attracts moisture". I live in Arizona BTW and in a arid climate.
It caught me off guard because I've left guns in my other cases and never had this problem before!