This old Kaintuk Long Rifle that the old man left laying around had been shot so many times during its 'hey day' that the end of the barrel had begun to flare out (ie. tapper to a wider than original opening). Could this be 'glass blower speak'?

Also, an end piece that screws onto threaded pipe which enables the pipe to be mounted perpendicular onto a flat surface is called a flange. Same root, perhaps?