The old 0000 steel wool and a variable speed drill trick. Many years agao I had a Remy 1100 gummed up pretty bad with plastic fowling. Placed a serraded wood dowl in my drill, wrapped it with the 0000 steel wool. Then soaked the steel wool with Hoppe's and went at it. Five minutes later my barrel looked better than brand new (it came from the factory dirty). Not sure I would do that with a crome lined barrel. For some reason I don't understand, I never had a problem with plastic fowling after that in the Remy. My two Benelli's, a 20 guage short stock Monty and an early H&K S90 M1 in Police configuration never had fowling problems. Both barrels in my Benelli's look pristine.
Retired Federal Law Enforcement
"I hope'n there're be Quail hunting in Heaven, or I'll be mighty disappointed."