It's probably not the gun.
I had an Armalite last year that spit out cases that looked EXACTLY like that....
With HSM ammo.
Try some other loads before you freak. If FEDERAL 556 stuff, WWB and Hornady all do the same thing - then you know it's the gun.
But I think it's the AMMO in this case. I think the ammo is too hot on the pressure and forcing the bolt to open too soon. That's what it did to the Armalite. And it can be the loading is fine as far as charge goes... but it could be a wrong powder or a bullet setback issue that is spiking the pressure because of a weak crimp.
Clean and Lube the gun properly before you shoot it again.