To say a bullet (especially a 5.56mm bullet) tumbles is an oversimplification. They will "yaw" in a target or turn sideways. This puts incredible stress on the bullet and normally causes the bullet to break up or fragment at the cannelure (the weakest point of the bullet jacket). X-rays will show two large pieces and a "shower" of fragments.
In life, strive to take the high road....It offers a better field of fire.
"Robo is right" Fuzzball