I’ve used a 16” 223 AR on three deer. Bullet didn’t seem to matter if you stuck it through the slats, 40gr Nosler, 55gr Hornady SP, and 53gr TSX. I’ve also killed around 50 pigs in the last 2 years with 223ARs and a 222mag boltgun. I’ve used 40gr Varmaggedon tipped, 50gr Hornady SP, 55gr Hornady SP, 53gr VMax, 55gr BTips, 50gr BTips, 53gr TSX, 55gr ball, 75gr Hornady BTHPs, and probably others I’m forgetting, they all kill pigs from #40-250. Shot them in the front half and collect your critter.