Bad shaving in barrel

[Hollis]

I would bet my last dollar that that is the gas port. I can certainly see where one can be fooled into thinking that is a 'shoulder' of sorts though. The lands & grooves (along with the copper fowling, carbon deposits and the angle of the image) can do a lot in creating a bit of an optical illusion that I believe one see's after looking at the photos.

Yes. I believe that is exactly what happened. Thanks to all for the help!