I keep hearing of this term "battle rifle"...as if the 5.56 in the A2 isn't able to reach out past 350 meters.
Of course the standard comment is "well, 5.56 might reach out past that but it won't do anything"....
Well, putting M855 up against M80 ammo at 550 meters, one will find out M80 is LESS effective against open troops and light body armor than M855.
Then it degrades into wound trauma and how a .308" diameter hole is more effective than a .224" hole and how a 147 grain projectile is more lethal than a 62 grain slug...
Survivability on the battlefield means hitting your enemy before he hits you. If I am trying to reach out 500 meters and can recover faster from each round than my enemy can, I will get him first. Even a lowly .224" hole in a non-lethal area will severly limit the enemies ability to do the same to me.
In close range combat, the AR might make an acceptable assault rifle but its not anywhere close to a Thompson. It is the premier battle rifle, capable of point target engagement to 550 meters right off the shelf.