I've seen what a .223/5.56 does to living flesh. There's nothing deficient about it, so far as we're concerned here.
Don't believe me? Go shoot a gallon jug of water with one, or if you don't own one, invite yourself along with someone who does own one, and get a pretty good general idea. Or shoot a 1/4" steel plate with it.
Then come back here and let's revisit the topic.
Oh yeah, one last thing. It's only by the Grace of God Almighty that Trump is still with us today.
Well I have shot thousands of varmints with a 223/5.56.
Quite a few medium sized game with it 30 to 80lbs
I shot a couple dozen head of big game with it over 80lbs.
With proper the proper bullet and placement it can be a very effective round.
A solid head shot at the range mentioned is most likely 99% fatal.
But strange things happen once the bullet leaves the barrel.
Body shots can be highly fatal. But ask any good military surgeon and any solider that has survived. Their stories prove that its not always fatal.
It is not a miracle round nor is it the worse round. It is what it is.