Another vote for Boretech Eliminator, been using it for years and it's a great product. It's biodegradable 100% non hazardous, safe to use indoors...
It's a surfectant, gets under the fouling and lifts it off of the barrel steel allowing it to be pushed out with a jag. You can leave it in the barrel overnight, it will not damage chrome lined barrels, bluing, plastic...
Try some, you won't be disappointed.
^^^ What CW308 says ^^^"...KG -1 first for carbon KG-12 for copper...."