Keith,
At first, I did not fully understand your question, so after some research, I located and read the thread below on this site and now I understand your question.
http://www.doublegunshop.com/forums/ubbt...nt=2&page=2 A fine line can be seen in proper light and in close up and enlarged pix. This pic of the Talley sight in the Talley compatible grooves does show the line on the right barrel:
Left barrel view of Talley grooves and thin line around barrel:
I do not know whether the McGowen barrels were threaded or soldered in, but until your question, I did not even see the joint; thanks for the education!
Also, the gun maker has a backlog of more than a year and has asked me not to post his name, so I must honor that promise.
