RE: deer slugs in a full choke ????
It's safe with a rifled slug, but like everyone else says, the accuracy probably won't be all that great. Although, some of those older guns will surprise you with how accurate they are. I have an old sears and roebuck shotgun that shoots slugs great out to 50 yards, and an old western field shotgun that will shoot anything a foot low and to the right. Try it and see what it does. As long as the barrel is in good condition, it should be fine.