Got a buddy ask me about deer hunting with an ar, so I figured I would get thought on this. I know many people hunt with ars and they have the accuracy to do it but would a 556 or .223 be able to drop a deer at say 200 yards? I know many factors come into play but let's say he is using good hunting ammo and using a scope on an ar. While on this note would a 16" barrel be advisable or should he step up to an 18".