Quote Originally Posted by Kiwigrunt View Post
No. Through hard cover like walls and foliage 7.62 is far superior to 5.56.
However, through armour (think helmets and Crisat) SS109/M855 is superior to 7.62 ball because of the steel penetrator, which means we are comparing a ball round to a semi-armour piercing round.

The issue that Selil brought up pertains to the behaviour of the rounds through tissue (bodies). Both M193 and SS109/M855 behave very inconsistently. 7.62 ball does too but to a lesser extent.
I have hunted goats with both M193 and SS109 with very different results. If the round is allowed to travel a fair distance through the tissue, or hits bone, than it will tumble and disintegrate (provided the velocity is adequate). When that happens it tends to turn the goat inside out (I exaggerate somewhat). If not, and that is most of the time, it will indeed just drill a pretty little 5.56 mm hole clean through. I have stopped using these rounds for hunting because it is not very goatistically correct. Softpoint is way more consistent and will start to mushroom pretty much straight away.

So this is really more a function of bullet design rather than calibre. Mk262 is apparently more consistent and far superior to M193 and M855. And a few others have recently been designed to help overcome these shortcomings. With a well designed 5.56 bullet it is likely that it will outperform the old 7.62 NATO, in tissue anyway. Destroying hard cover and the ability to maintain its trajectory though foliage are still a different matter. There you can’t beat the mass of 7.62.
The 5.56mm was introduced into Vietnam in 1963... and nearly 50 years later they are still attempting to find the right ammo to use. You go figure.