Aside from the mechanical Lewis remover I have had really great luck with this foaming remover. Left overnight the lead will turn mushy gray on the edges and help it lift out of the bore, may have to repeat on heavy leading but it sure makes it simple and easy, it will also do the same for wadding from shotgun bores. This is the only one I have used, others may work as well or better? But this I know has worked better then I expected. https://www.amazon.com/Gunslick-9209.../dp/B000U3Z5TI
Instructions say you can not use it on a gas operated semi, you can, you just have to take the gun apart first otherwise the foam will work into the gas system and gum it up if left there. Make sure the barrel will set level so the foam won't run out one end and lay down a barrier to protect your bench, I use a trash bag with some newspaper on top, when done I can roll up the plastic & paper and drop it in the trash can.
I bought an old Nagaut M44 that was loaded with fouling and some pitting, without fear I could do more damage I put this foam to work on it. It took many, many repeated over night soakings, brushing and replying but the cleanup in the end was amazing. It got under the copper fouling along the rifling, lifted it so it would brush out, then came out old powder fouling that had been covered and encapsulated by the copper fouling, I'm sold on this stuff. But for the end of the day pistol shooting lead bullets, a quick pull with the Lewis will take out any lead and keep it from building up. Never tried it on a polygonal barrel but I can't see why the Lewis wouldn't as good and maybe even better then with sharp rifling.
Another tip that might help some, I take an Otis pull through kit with CLP to the range, after the last shot while the bore is still warm I'll pull a few soaked patches and leave a coating in the bore letting it work during the trip home, any edge to cleaning I'll take. I also take smaller patches, double it over, put one against the chamber and slowly close the action on the patch to keep crud from running inside and roll up one lightly coated patch and tuck it in the muzzle, keeping the gun bags clean.
Thanks my 2 cents! Let us know what ends up working for you! I'm always looking for something better!