Yeah, I'm with RR on that one. You will have MANY people tell you that the .223 is fine for deer with all this new ammo and such. I'm of the opinion that it's just too light of a round. CAN it kill a deer? Yep, many have been killed with that caliber. But SHOULD you? Really, no. Placement is key to any shooting of live game. But a .22 caliber is just too dang small and perfection is needed with every shot. No-one is perfect. Plus I am kind of gathering that you don't re-load your own ammo and I am not sure on this (RR will correct me if I'm wrong I'm sure) but the factory ammo that is out that is minimally acceptable for whitetail may not even feed well in your AR. The Over All Length for the heavier LONGER bullets may be just a touch too long. Been a few years since I bought a box of ammo other than .22 long so I am a little out of touch on that one.