I have an older Browning Belgium A-5, and have a full choke barrel. I watched a hunter with the same gun put steel shot through it and blow the end off. I asked a rep from Browning about this, and he said that those older barrels are made of a softer material than the metal used for steel shot. He said sometimes you can get away with shooting steel forever,and sometimes one or two shells will blow out a barrel. I now shoot Bismouth shells through my old Browning, and they pattern very nice for waterfowl. Next year, I'm going to spend $300 and buy a replacement barrel that comes with fiber-optic sights and adjustable chokes. The year after that, I'll buy a slug barrel for it. Then, I'll never need another gun. 
And I'd NEVER shoot slugs out of a full-choke, unrifled barrel. NEVER
And I'd NEVER shoot slugs out of a full-choke, unrifled barrel. NEVER
