My Grendel build

[VASCAR2]

I think you would be safe to fire brass cased ammo like Federal or Hornady. Even if it was over gassed a few rounds shouldn’t damage anything. I personally want a rifle/carbine that will function in sub zero weather so I tend to put up with a more brisk action which is likely to occur in hot weather. The 6.5 Grendel AR-15 don’t generate a lot of recoil and I’m normally not as concerned with fast follow up shots or rapid pairs with my 6.5 Grendels.