[templar]

Muzzle velocity is not decisive, the behavior of the bullet in the target's body is.

FMJ bullets generally don't fragment in soft tissue. The 5.56 FMJ round is so deadly (for it's size and weight) because of what is known as 'bullet yaw' or tumble at high velocity (capable of tumbling over several complete times in the thickness of a body). The 5.56 does indeed lose a lot of it's yaw at lower velocities. I like the Russian idea they have with their little 5.45 FMJ bullet of having a hollow cavity behind the nose of the full jacket that upsets when it hits (I suspect a loss of ability to penetrate hard barriers). Best of both worlds; FMJ for military legality and Hollow/soft point performance for high lethality in the same bullet.

[BushMeister]

That's nonsense, and has been thoroughly debunked. The 5.56mm round is only more lethal than 7.62 x 39mm, 7.62 x 51mm, etc. when it FRAGMENTS in the target's body. And IT WILL fragment, it it's going fast enough when it hits the enemy. The "yaw" inside the body is what causes the bullet to break akong the cannelure, but ONLY when it impacts at sufficient velocity. See the AR15 link I listed in my previous post. Ballistics test have been done that clearly back this up.