I don't see any reason why you couldn't do that so long as the barrel wall of the breech end is thick enough. I have a 20 GA barrel from an old single shot breech loader that I plan to use to make a shotgun barrel for the Swamp Dragon. The breech end of that barrel is really beefy, so I have no worries there. What I don't know is how hard it will be to cut threads in a nitro barrel.