In reply to your questions I clean every 1 of my firearms the same way and use hopps cleaning proudcts on every one of them my wife has our room set up with a hunting motif so it is displayed on the wall with my browning no rust on it both shotguns were used on the same days of shooting so exposed to the same conditions and cleaning procedures yes it is the black finish and the rust is on the outside not inside of the barrel so I would assume I got maybe the 10% that had a factory defect in the finish (ohhh ya I forgot there has never been a company in existence that has produced a so called lemon or 1 item of a product line that had a defect) and like I said all of my firearms are stored and treated the same way an in the same room(weatherby 7mm, remington 30-06, remington 22, early I believe when I researched the serial # 1935 belgium browning A-5, S&W 357,ruger .45, whinchester 30-30) So I am not a newbie with cleaning firearms the Marine Corps made sure of that 20 odd years ago.
My complaint is that Benelli will not acknowdge that it could be a problem with the finish and as to impacting the sales no I do not assume my post will bankrupt them but if I save 1 person the frustration of a rusted barrel then so be it