What the heck is going on here?

[spike camp]

A friend told me he traded some labor for a AR platform 6.5 creedmoor.

I haven’t had a chance yet to check out the rifle, but my friend said the casings were showing some markings.
I didn’t know the severity until last night when I received these pics…

 

[Pilsner]

Following. A buddy's AR in 6 ARC is doing nearly the same thing. We have fiddled with the gas settings to no avail
Hoping this thread will generate ideas.

 

[HandgunHTR]

Looks like the rounds are sitting high either due to the feed lips being opened up, or the mag is sitting high and the bolt is running over the rounds as it closes.

 

[spike camp]

Looks like the rounds are sitting high either due to the feed lips being opened up, or the mag is sitting high and the bolt is running over the rounds as it closes.

Thanks for the input.
I was thinking under-gassed, and the reason for the long lug marks. Called bolt over ride?

Mag issue makes sense.
Any input on how to check for mag feed lip height across different brand mags?
I do know my buddy has a different mag he hasn’t tried yet.
Thanks for your thoughts.