I use brake cleaner and a brass brush. Make sure you get chlorinated brake cleaner. The chlorinated kind will get the plastic out and of course when you are done coat the bore with gun oil. Brake cleaner is a lot cheaper than gun solvents that work just as well.
I use a bore snake after I shoot, every time. When I start to see plastic streaks from wads I use a brass brush wrapped in steel wool with the cleaning rod chucked up to a drill motor.
A little Kroil in the barrel and a tornado brush on a Dewalt Drill works well for removing the plastic.
Rarely-very rarely-do anything but swap out the chambers. When I do, 0000 steel wool, on a brush of the right gauge, with some solvent, then a dry patch.
Have used the above method and there is probably nothing better.
A few years ago I bout an 870 Marine Magnum. The previous owner had obviously beef stuffing the extended mag full and then dumping the magazine as fast as possible. I've never seen a barrel with that much plastic in it! Chamber to muzzle, not a speck of bare steel.
I uses a lot of carb cleaner and a 0000 steel wool wrapped brush on a rod in a drill motor and it worked great. The carb cleaner did a decent job melting the plastic and the brush gave me fresh plastic to work on.
When I used to clean the 4-H trap shotguns I'd use Brownell's Shotgun Wad Solvent. They had only the liquid then. Swabed it in and let it set a few minutes and bronze brushed all kinds of black plastic out. It seemed to me it worked its way through or under the fouling so the plastic released from the barrel. The screw-in chokes cleaned more conveniently with a brass scraper I made.
I don't know if it was the solvent or Ed's Red I finished with but after I got the barrels cleaned up there was less fouling and it pushed out more easily every week.
Don't forget the chamber with a chamber brush.
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I see they changed the bottle for the liquid version and charge less for the gel. The liquid is hard to keep captive and can do nasty things.
A few years ago I bout an 870 Marine Magnum. The previous owner had obviously beef stuffing the extended mag full and then dumping the magazine as fast as possible. I've never seen a barrel with that much plastic in it! Chamber to muzzle, not a speck of bare steel.
I uses a lot of carb cleaner and a 0000 steel wool wrapped brush on a rod in a drill motor and it worked great. The carb cleaner did a decent job melting the plastic and the brush gave me fresh plastic to work on.
Never seen such rough bore as on one of them. I can just imagine they collect plastic like crazy
If they have been fired or subjected to moisture, I clean them after every outing. With my target shotguns that usually means every 3-4 boxes of shells. I use Hoppe's #9 on a patch wrapped around a brass brush. A couple of passes in each barrel and it's done. If you keep on top of them you won't need anything more. Never needed to use a power tool to clean a shotgun bore, it never would have even occurred to me. I use the boresnakes only when I'm away on a hunting trip. After awhile cleaning a bore with them is akin to taking a bath in a septic tank.