the rifles in those game pics are not your typical AR's, they are chambered in specialty cartridges, one is a 25 wssm, the other is a 458 socum, my 223's/5.56's will suffice for deer with the proper loads but I don't use them much except for varmints and such.
I use my 458 bear hunting with dogs, the 25 for deer hunting if the conditions do not warrant getting my long range rifles out
RR