Lets liberate Iran.
And Hornet33, there are weapons out now that are really quite amazing. I personally like the Russian assault rifle that can fire two rounds out of the barrel before the recoil gets to the shooter.
Or for pure tissue damage, how about replacing the aging m16 with some of the flechette firing rifles designed in the 1990s. Those things were brutal.
I even think the M-14 is still a better rifle than the M-16a2. Todays soldier is bigger than his 1950s counterpart (my grandfather wore a size 7 boot in the army during WW2, I wear a size 13). Thusly, from a physical standpoint alone, our soldiers would be more capable to fire a fully automatic 7.62mm rifle.