When I clean the bore of my 870, and it has a large amount of plastic buildup, I first swab th ebore real good with Hoppes, bore cleaners, etc. The, I let that soak, and clean the rest of the gun. After the barrel has soaked, I chuck a cheap cleaning rod in my cordless drill, and use a bore brush. After a few passes with the bore brush on the drill at full speed, I swab it out once more with the bore cleaner. A clean patch later, and its like new, with no residue.