My take on it from the pics. : Possible bullet striking at where there is supposed to be a small smooth radius at the chamber entrance.
Possible bullet hitting on magazine front lip and perhaps bullet hitting on a sharp corner at the feed ramp.
The marks look different from other barrel extension gouges that I've seen. As it's near the tip, unlikely it's something inside the actual chamber.
DL42, what magazines are you using and is there evidence at the front inside lip of foul play?
The radial marks at the base appear to be where the bullet is engraving on the lands?
Possible bullet hitting on magazine front lip and perhaps bullet hitting on a sharp corner at the feed ramp.
The marks look different from other barrel extension gouges that I've seen. As it's near the tip, unlikely it's something inside the actual chamber.
DL42, what magazines are you using and is there evidence at the front inside lip of foul play?
The radial marks at the base appear to be where the bullet is engraving on the lands?