***There isn't any "buzz saw" effect as seen on TV. Most 223 rifles will have a twist rate of 12:1 up to 14:1. ***
I don't think they have produced any .223 rifles with that loose of a twist in the past ten years. Most range in the 1 in 8 to 1 in 10, some are as tight as 1 in 7. The military found that the rounds destabilized too quickly in colder weather and accuracy went down the hopper. They tightend up the twist and other rifle makers followed suit.
Even FMJ military ammo breaks up and causes pretty good wound damage out to 200 yards providing the barrel was long enough to have decent velocity.
"Even FMJ military ammo breaks up and causes pretty good wound damage"
It would take more than bone to break up a FMJ 223 (unless you got those junk, electro-plated bullets). It would take a more solid object to do this such as a brick or concrete wall.
Yes, twist rates have come down over the years and bullet stability depends upon the twist rate, bullet weight, length and velocity. Spin a light weight bullet too fast and it will loose it's jacket in flight, go the other extreme and it will key hole. You have to either buy what you want, or shoot what the firearm likes.