I had a customer bring me spanish 10g shotgun that he had bought cheap. It had already been coated with some spray on gun finish at some time. He wanted the novelty of having a 10g coach gun. JB weld worked fine on the massive hole left behind when shortening the barrels. And i was fine woth it given what the gun was.
Of course soldering in a keel would be the proper solition if the job called for it.

B.Dudley