In the right hands, and where legal, the .223 woodchuck round is capable for taking big game. I'm sure in Southwestern states where critters are diminutive in size the .223 serves them well. Better cartridge choices like 7.62x39, 6.5 Grendel, .308, .243 in an MSR platform might be better.
My cousin in MD was excited because he can now add another AR to his growing collection, as he's building a .350 Legend for deer hunting since MD legalized straight-wall hunting cartridges.
I've been to many "deer camps" in my day over the last five decades and have yet to see anyone using an AR-style rifle for deer/bear here in the Northeast. I've seen Browning BAR's & BLR's, M700's, M70's, M760s' & M742;s, 336's, M94's, Ruger .44's, Savage 99's; but oddly not one AR15. Could be I'm hanging out with the wrong crowd.