Although I had a .223 Interarms Bolt Action and a Colt AR-15 HB, I never used them on deer. However, my brother has used an early Colt AR-15 (no forward assist), and his son used it to kill a couple of deer. My brother usually used an '06, but took a header out of a tree (about 30' up) during bow season, broke elbow, couple of ribs, so he anticipated too much pain if he used the '06 during the gun season. He found a blow-down, used it to support the AR, and shot it one handed. He reported it worked well. He always had a lot of faith in the AR as to its effectiveness, having seen the wounds it caused as a medic (V.N. 3-tours, 2 of which were in a LURP unit, in country).