I asked a GI out of Ft. Lewis the other day his thoughts on the AR platform . . . . "IT SUCKS!"
OK, expand on that, please. He laughed, said in most states you can't use the .223 to hunt deer and deer don't shoot back, so imagine yourself in a fire fight against people who are doing there best to kill you and Uncle Sam issues you a weapon that isn't big enough to hunt deer with. He also said they are talking about going to a 6.8 round but that the 6.8 lacked speed and distance capabilities. So what round/rifle do you suggest, I asked? The 7.62 NATO in a modern M-14 with a plastic/synthetic stock. In a carbine version, 16" barrel, it would be accurate out to 600 yards and capable of killing at that distance which is extremely doubtful in a 5.56.
I've spoken to guys back from the sand box that feel pretty much the same way, the round is too light to guarantee killing another human being, unless shot multiple times. Another offered, when shooting to hit something it is good to know what you shot isn't going to get back up and shoot back. Why expend multiple rounds? Insurance.
Me? I like the AR, have two and a bolt gun in .223 that I use of ground squirrels, coyote, etc. My reach out and touch something rifle is a 700 Remington in .308. Been looking at the R-25 and Springfields . . . Ain't made up me mind on either yet.