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borescopes highlight issues. Often they do that before those issues manifest themselves with regards to a rifles accuracy. By the time a gun does no longer shoot well because of corrosion/pitting it...

rust

For "unknowns" having different perspectives tends to be a good thing. And the 90 degree image should give you a nice close-up. Problem with some of the cheaper "borescopes" is that the 90 degree...

I reckon give it a good clean with some boretec and see afterwards.

dont have a 90degree mirrow with your borescope?