Originally Posted by BV

M-16 shoots a .22 caliber bullet and wounds it's victims more than it kills. A wounded enemy is better than a dead enemy because a wounded enemy takes 2 or more additional enemy soldiers to care for him where as a dead enemy does not require anyone.

Also US went to the m-16 .222 caliber round because soldiers can carry about 30% more rounds with the same weight as what they were used too. They used to use .308 rounds (7.62mm x 51mm) in the M-14 which is the same caliber as an AK-47 round (7.62 x 39mm). just slightly longer casing and powder lengthening the case to 51mm

All of you I'm sure have heard of the 30-06 (M1-Garand) This is what US used before the M-14 .308. Still a 30 caliber bullet just slightly longer case yet 7.62 x 59mm. This is the grandaddy of all the 7.62mm 30 caliber bullets.

For flat out kill power any of the 30 caliber bullets are far superior than a twinky m-16 .222 round as it's only .22 caliber, very small, but very very fast and when it hits your target it tumbles. So you hit them in the leg it might end up in his gut wounding him even more. You hit the same target in the same spot with a .308 and it will most likely just blow the leg off. Hit him in the chest with a 30 caliber and your kill factor is much higher than the little 22 caliber m-16

To put it simple, bigger is better.