I've fired a lot of .223, and I've never seen ball ammo fragment. On the other hand, I have seen one tumble, AFTER hitting the target. Fired a round into a line of water soaked phone books. It went in about a foot and blew out one side at a 90-degree angle. The recovered bullet was bent in the middle, also at about a 90-degree angle.
It blew one hell of a ragged hole, BTW. Although it was NOTHING compared to what I did to a similar line of phone books with a .30-30. The difference was that the .30-30 made a massive wound channel in a straight line (totally destroying 3 phone books at its largest diameter), while the .223 was clearly tumbling. It was one ragged, jagged hole.
You should have seen what happened when I used a .223 hollow point. It went in about 8 inches and basically detonated. Soaking wet yellow paper flew in every direction, about one phone books' worth. There was no round to recover. It was ugly.
I've never seen ball ammo that doesn't fragment.
That's what it's designed to do.
Past 400m, velocity begins to drop off quickly and that's the key to fragmentation. Perhaps the dense phone book material kept the bullet from splitting. My XM193 will detonate in water.