I've owned several M24 Savage combination guns. If they are regulated at all from the factory, it is pure coincidence. They are the poorest built combination guns I have ever come across. I suggest you try some sort of spacer or shim on the front barrel band, to separate your barrels a bit. Perhaps a thin strip of metal foil on the top of the shotgun barrel and inside the barrel "clamp" . Worth a shot anyway.
