If you read reports of our urban combat in Iraq the .223 gets set aside when someone can get an AK in 7.62X39 in their hands.
I have a Mini-30, and it is just a deer gun. The 7.62X39 is almost a direct equivalent of the 30-30, except has a spitzer instead of a blunt nose (so the rounds don't pop in a tube mag).
Now, the 30-30 is made even better with rubber spitzer tips that wont crush and detonate the rounds in a lever gun and give the round better aerodynamics.
The 30-30 is an American West round from way back, invented by Americans to kill Indians and deer. By Winchester.
No other round on the planet bucked more bush and dropped more deer than the 30-30 Winchester. NONE.
The closest animal to man, in willingness to live when shot, body size, skin, etc. is the deer. And deer love to hide in the bush it seems.
The closest cousin in ballistics to the 30-30 is the 7.62x39.
If Stoner designed the M-16 to use a Spitzered 30-30 round in his space-aged gun, nobody would have batted an eye.
The key focus was ammo weight. One .223 round weighs LESS than one 9MM hangun cartridge and has rifle range with low recoil.
"Spray and Pray" never really worked. People shoot semi-auto or with VERY short bursts in real life. Hosing down targets is only to get to cover. If you want to kill something, aiming is necessary.
If I was dumped into a war zone, I'd take an M-16 chambered in 7.62x39 any day of the week. And I could then use bad guy ammo if I needed as a bonus.
My next choice, or even my first choice, would be vanilla .308. The .308 is absolute perfection in my opinion.
All the concepts and stories behind the .223 and "yawing" and spinning through bad guys and turning them into ground beef are great, provided they aren't hiding behind the thinnest of shrubbery.
Every old-school gun mag I used to drool over when I was 12, where it was printed in black and white on newsprint but had a color magazine cover, loved to have a .223 vs. 7.62x39 story every once in a while.
They'd shoot at targets through hedge rows, through steel drums, car doors with glass blocks set on the seat... And they all came away scratching their heads with why the .223 is the U.S. issued load.
The debate has been on since I was a young boy in the late 70s and 80's. I am not in the military, and I could only base my opinion on what I'd go deer hunting with.
If a vet can add to the discussion that would be probably the best thing...
Edit: If you want to see what a 7.62X39 M-16/AR in action (barrel rise etc.) you'd see that it would be a great round in combat. Go to YouTube... Very sweet guns.
Edit 2: Check out vs. videos between the 2 rounds as well. This was a basic one:
http://www.youtube.com/watch?v=5euXm5msz1Y&feature=related