5.56 was chosen for firepower over 'stopping' power. We wanted a 6.5 or 7mm preferring aimed shots over cover fire.
The Nato round can pierce armour but it is widely known to wound not kill, it's primary intention. It just pencils through.
But irrelevant in this discussion anyway.
I think the choice of the 5.6 was also due to shootability, the ordinary soldier will have a higher chance of hitting the intended target vs say a 7.62. The average soldier under stress will benefit from more ammo and lower recoiling rifle. Many reports that I read seemed to indicate that the FMJ from 5.56 tended to tumble and often fragment inside flesh rather than just pencil through. I also don't think wounding is an objective, main objective is to win a battle and avoid being shot/wounded.
Anyway...a 5.56 has way more "stopping power" than a 7.62 missing or out of ammo.
edi
