Guys, I really appreciate all of the information and pointers!

I haven't actually slugged the barrel yet, I have to pick up a small rod to drive the slug through first. But, I measured the muzzle quickly with my calipers and got .268. I will slug it properly tomorrow to be sure. I don't see any type of welding or anything that looks out of place.

Can anyone tell me what these marks mean? I know the QF6722 is the serial number and the crown is a proof mark that it has been tested.... I'm curious about the RE or RF, the circular stamp above the 2, and the circular mark above the crown. Also, in the top right of this picture, is that another type of stamp/marking or is it just a gouge?