I think some clarification on AR's need to be made. Because AR-15's are chambered in manydifferent calibers than just .223/5.56.
Many AR-15 calibers are easily capable of taking whitetail and larger at reasonable distances. I'll say 0-200 yards. Some will reach farther, but 95% of hunters shoot game at less than 200 yards.
.450BM, 6.5 Grendel, 6.8SPC, 30 Rem AR are several in SAAMI Spec cartridges.
Then there are less known "specialty" or wildcat cartridges. .45VRAP, 458 Socom, 50 Beowulf, 6.5BRX, .257 Bobcat, 7mm Valkyrie, .277 WLV and I'm sure many more. Then currently being developed is the .358 Yeti and .30 Sabercat.
The rounds I listed are no more capable or less capable than the proven .243, 7-08, .308,.270,30-06, etc. It's just that AR's are typically same weight or heavier and many people shoot the lighter recoiling semi autos better.