...the crap about wounds vs. kill and lighter weapon with more ammo, ya da ya da ya.
It has not proven out. The AR platform in .223 in all it's various configurations sucks for war. People who do the shooting want weapons that kill. They want weapons that require less maintenance.
Lo and behold.. wounded people tend to fire back!!
But first and foremost, you have to have the ability to hit a target.. doesn't matter what round you use. The military puts a lot less value on marksmanship training than it does say on the prevention of sexual harassment..
You have to "qualify" with your weapon once a year, usually taking up about 20 minutes of individual range time. that same year each soldier, sailor and Marine probably gets subjected to 4 - 8 hours of sexual harassment training.. than add to that sensitivity training and all the OTHER make them better people type training.. Some of the units I was in were a few of the lucky that got some exceptional training in some of the "fine arts", but most aren't as lucky..
I remember sitting in Germany looking at all these COOL thermal and passive night sights we had for all of our personal and crew served weapons.. Not once did we EVER actually attach any of these sights to weapons to zero them in with REAL ammo, yanno, because that would be too DANGEROUS!! Yet we were the most prepared units in the US, ready to meet the Soviet Horde!
That being said, and the 'mix' of soldiers we have now, the M-16 is as good a choice as the 9mm handgun.. You have to have a weapon in the system that EVERYONE can handle.. You can't have a weapon made specifically for your male 200 lb infantryman and another for your female finance clerk or the 90 pound female MP.. EVERYONE has to have the same weapon. And yes, tactically it makes no sense, but nobody's feelings get hurt so it's all good!