1-800-243-9700, Remphone.Work down the phone tree until you reach a real person.
I suspect Bubba and his Unholy Hacksaw from Hell have done atrocities to your barrel. The 11-48, being a recoil action, requires a certain amount of mass to make things work. My guess, Bubba realized he'd messed up big time right after shot 1 and traded it off.
Your choices are....
Trade it off to someone you dislike.
Get a new barrel from Numrich, etc, and move on. The 11-48 has lots of happy owners.
Or, get a qualified smith to install a Deluxe Polychoke and rib. This MAY add enough weight, though you may have to play with the rings and springs.