6.5 AR- Consistently dented and scraped cases cause?

[6.5G]

I shot my Bear Creek Arms (not very respected and known to be overgassed) upper for the first time. Everything functioned fine. I Hadn't the context to note the ejection pattern, but I did collect brass knowing it can be diagnostic. I found a small dent mid-case, and scraping. The cases were also darker upon ejection than I've found with other semiautos in my limited experience. Does this tell you much? (video of cases in different light at link)

 

[1moaoff]

Pictures move when I zoom.
Quick guess. Dent in the side is from shell deflector. Scratches may be from mag lips and feed ramp