5.56 loaded with varmint-type projectiles such as Sierra Varminter or Gameking, or Nosler Ballistic Tip are devastating...ever see what they do to ground hogs? I think that even a peripheral hit with one of those would take the fight right out of someone, make 'em change their mind in a hurry. The Geneva Convention does not allow those kinds of bullets in war, so our boys in uniform are stuck with ice pick-type projectiles; so in that situation, I'd venture to say that bigger IS better. I'm a .30 cal kind of guy myself, but I have lots of varmint-type bullets for my AR just for kinds of emergencies stated previously. My wife and kids can use the AR and the mini-14 while I use the .30 cal (M1A).