for over 20yrs I have used a Marlin 120 12ga with a 28in mod barrel for duck and pheasants. I bought the 28in barrel directly from Marlin in late 80's as it originally was handed down to me by an old uncle with a 36in full choke barrel. It has served well but my son has now taken over my Rem870 with a slug barrell. Thus, I need a slug barrel for my old Marlin 120. I have looked at several sources and no one seems to have such a slug barrell in stock. Any advise?