Agreeing with horsesoilder, 5.56 does the job, real combat vets who go bang bang to the baddies love the round, they stick with it and love the M4/M16 platform. Change isn't coming for decades. 5.56 does the damage and takes the opposition out of the fight, bigger isn't always better. Does the 6.8 have amazing ballistics and trajectories, yes and probably out perfoms the 5.56, but it has been field tested and it's just not gonna happen. It may be used for SF or certain operators, but as a true replacement for the 5.56 it's momentum and chance have faded. If you are looking for the best performance then maybe all weapons should be changed to the perfect .408 caliber. But realistic logistics, how much weight vs quantity of ammunition a G.I. has to carry, more is always better for the regular grunt. The US used larger rounds before as standard caliber, 30.06/308, but the troops wanted a better round and they got one and it's been doing pretty well. It's easy to be the internet quarterback spouting numbers and trajectories, but the main objective of that round is damage, that little bullet does some MAJOR internal damage; but concerning the guy with the boot in the mud (sand now) ask him what he wants to carry and use, especially if he's got that bitch of a radio in tow too. Just my opinion, I really do not take weight from someone who's "read" or "heard from a buddy" or "compared charts" when it comes to a MILITARY weapon or round for a MILITARY application, 5.56 and M4 platform are pretty much kings of the road until a new weapon is tested for a couple years, then a couple more.