I've noticed some scratches on the inside and bottom side of my upper receiver. I can't think of what would be able to get into these locations and cause these scratches, so looking for some input.
This first one is the rear locking pin area. This part normally sits inside the lower, behind the trigger. What could cause this scratch?
Scratches are highlighted in the red circles. Some of them I've touched up, but no idea what could cause these:
Last picture here is of the lower:
This first one is the rear locking pin area. This part normally sits inside the lower, behind the trigger. What could cause this scratch?
Scratches are highlighted in the red circles. Some of them I've touched up, but no idea what could cause these:
Last picture here is of the lower:


















































