Ar-15 gurus, help me out please

ker2222

Full Member
Full Member
Minuteman
Sep 3, 2004
638
64
52
Hastings, MN
Doing some cleaning and maintainable and saw this on inside of upper reviver. What the heck is it? A little cosmetic issue Or something serious.
CE7CE96E-D479-4C10-8124-BFDBC981F032.jpeg
or something serious?
 
How many rounds on it? The coating wear is normal, but it looks like you had a few jams. Post a pic of the bolt face.