Never use a pipe cutter on a shotgun barrel. If you do, the muzzle will be sharply constricted. If you file the constriction out, the muzzle will be thin. Either way, the muzzle will be work-hardened.
Shotgun barrels should be cut with a hacksaw, filed square, polished, chamferred, and the sight reinstalled.
Don't sell any of the parts, as you probably will want to reinstall them later.