Plumber,
Thanks for the insight. here are images of my new tube, just received in the mail There is no slot for the pin on the back side. What you say makes sense, if the pin was already installed for the sight as it is on my head casing, I will need to mill a small slot at the 12 0'clock position to accommodate the pin which will correctly position the tube in the head casing. Does that sound correct? Will confirm with you before beginning.








Last image showing the end milling to accept the barrel seating.