H&R won't fit Rifle barrels other than 357mag and 44 mag on a shotgun frame since the shotgun frame is not heat treated to handle the pressure.
Read quite a little bit before I posted. I get the gist of it.
Just a little constructive criticism. Have you heard of, less is more? The different colors and multiple sizes of fonts is hard to sort through. There is no way to tell what is important to know and what is not. My question is really, what would be the guess of a shotgun of that age? Is it definitely a SB1? It may be as simple as, "your gun will shoot shotgun barrels or a 45 long colt. Nothing else"
That is kind of what I thought, pop.