The indentation on the side of the 6.5 Grendel case is more than likely caused by hitting the ejection port opening or the case deflector. It is very common for brass to get dings from cycling. Many times the case mouth with have irregular shape from hitting the deflector or other part of the upper during the extraction/ejection cycle.
Small dings normally wont adversely affect brass case life. Tuning your adjustable gas block can help, plus you can put soft velcro on the deflector. Any place the brass hits the ejection port opening or deflector will leave a brass smudge.
This video shows a AR-15 in 6.5 Grendel being fired.
https://www.youtube.com/watch?v=YbXBDe1argo
Small dings normally wont adversely affect brass case life. Tuning your adjustable gas block can help, plus you can put soft velcro on the deflector. Any place the brass hits the ejection port opening or deflector will leave a brass smudge.
This video shows a AR-15 in 6.5 Grendel being fired.
https://www.youtube.com/watch?v=YbXBDe1argo