PS The .223 with the right bullet and the right twist in the rifling can be devastating within about 300 meters. The old 55 gr FMJ in a 1/12 twist barrel was a better killer than the 62 gr steel core penetrators in a 1/7 twist. When the heavier bullets came out to increase the effective range of the M-16A2, some of the traumatic wounding of the 5.56 in the M-16A1 was reduced. It just punches a hole most of the time.
The old 55 gr in a 1/12 twist was barely stabilized. It tended to yaw on impact and create more lethal wounds. It was a tad faster, too. I like a 1/9 twist. It will stablize the heavy bullets but still fires the 55 gr accurately. I had a Colt Match Target in 1/7 that only was accurate with the heavier > 60 gr bullets. I don't remember all the stats, but that is the problem in a nutshell.
Expanding hunting type bullets may not be great for armor penetration, but they help make the .223 much more lethal against soft targets. A lot of people have been killed with the M-16. The mouse gun is still deadly, it is just not as deadly as a 7.62 bullet in many circumstances. I'll shut up now.