Any ideas?

One of my ARs is a long range "sniper" rifle. It has a 20" barrel on a DPMS Low profile "slick" upper. No shell deflector.



As my shells eject I believe they are whipping back around, 180°, and smacking the mouth of the brass on the upper. This can leaves a slight flattened deformation. As I am saving this brass for subsequent reloading I find this undesireable.
I am assuming that I could/should do something to lighten up the cycle pulse, if possible, to minimize this. I am considering changing the buffer and maybe the spring. I am not shooting hot hand loads. My beast's prefered load ia an HSM 75gr @ approx. 2800 fps.
I would appreciate any ideas from field.

Thank you!