The easiest, quickest and best thing I have used to clean a shotgun barrel with is WD40 and a boresnake. For some reason this taboo elixir works on plastic wad buildup, I simply hose the inside of the barrel let sit a minute, run the snake back and forth 3-4 times and presto shiny tubes.
+1. I also use WD40, but only on the bores. I spray it down let sit for an hour or two. Run a patch (I use wadded up toilet paper) thru the bores until the bores are shinny. Sometimes I use a brush (when the bores are really dirty). Then I run a oiled patch thru the bores and I'm done. It works for me.
Good Luck!
Greg
