I was toying with taking an AR-15 hunting last season, simply because I was really familiar with my ar and it was an extremely good weapon and of course it will kill a deer, but it gives very very little margin for error, so i decided to go with my other option (7.63x54r) which gave me a ton more margin.
Theres no real argument for the .223 no being able to kill a deer, hell a .22LR is CAPABLE of it, but the chance is so bad about getting the shot right it makes its use unethical. On the .22 LR i mean.
And I always crack up when people refer to my ar-15 as an assault weapon or "built for combat". I have yet to see a semi-only M-16 or M-4 in the Army, but hey i havent been in very long at all, maybe im just weird. lol
"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself."
-John Stewart Mill