The Birmingham proof house regularly proofs guns at .018. They will dent easily but barrels will proof that thin.
Mike, Don't you think you should clarify at what point on the barrel this .018" wall thickness is? I don't think Birmingham will proof a barrel with .018" thickness, 3" or 4" ahead of the chamber. When people ask about barrel wall thickness, they really need to be told at what point on the barrel these measurements are safe. I have my own guidelines, but they may not be correct. They do however work for me.
