I think there is some merit for production, non-lined, barrels having seen the improvements first hand. It would come to reason for lined barrels that the bore would be pretty clean before treating, else any residue would be treated as well and possibly cause issues long term.

I plan on slapping a good scope on my sport barrel and taking it to the range to see what kind of groups it's capable of. I hear opinions that short barrels aren't typically accurate, but a lot of it has to do with the load and bullet being used. I tricked my Sport out to be a quick reaction coyote killer, shots typically 150 yards or less. If they take off running, just means I get to shoot more bullets at them before they get out of sight!!! 8-)