Follow up to my reply / post on page 2
One of my boys did shoot a deer with the .223 out of a AR.
The doe was just 15 yards away and went only 20 yards after the shot.
Rifle was a Windham SRC with a Bushnell TRS-25 red-dot.
He used my handload, a 60 gr. Nosler Partition chronographed at 2,807 fps from a 16'' barrel.
The bullet made small entry and exit holes, but did significant damage to both lungs.
9mm +P minimum. 40, 10mm or 45 preferred.