I know folks hate to answer a question like this one; too many variables and not much literature. Don't even try to get an answer out of a gunmaker or ammo mfgr.
I think the gun is stout enough since it was built to handle the rifle pressure and recoil, so the question is the shotgun barrell. Based on information to the effect that the longer shell in the 2.5" chamber does not in itself cause an appreciable pressure rise I don't see how the chamber length is an issue. The payload of the slug is 1oz which shouldn't be a problem. The only problem I see is the higher pressure of the Saami spec modern slug shell.
I'm not going to hold anyone responsible for what I may decide to do, but I'd like to know if everyone thinks I'm making a big mistake.
