JimR,
"AR15/.223 Rem not a battle rifle ... "
I'd disagree. Although nowhere near the punch of "a real gun," shots through the pelvic girdle will make 'em squeal a bit & the phycological impact re "their neighbors"
does/will have a desired impact.
Don't think the .223 was ever brought into the military inventory as "a killer." Moreso to wound & tie up that extra 2-3 folks gettin' their buds outa harms way. That ties up many more re logistics than does one straight kill.
Too, an AR set up to do prarie dogs at 250+ is certainly capable of hitting a, say, 5" circle at 300.
With the l'il "mouse gun," ya just have to be a bit better on the trigger.