5.56x45mm is too light for consistent kill shots on whitetail deer. A kill shot can certainly be made, but you take a much bigger risk of just wounding the animal, which is unacceptable to me. My AR is chambered for 7.62x51mm, which is much more than adequate for deer.

The essential American soul is hard, isolate, stoic, and a killer. It has never yet melted. ~ D.H. Lawrence