I, for one, am glad we have never had a real all-out shooting war against the Russians. Their 7N6 is a nasty little ball round, designed from inception to tumble. To see just how much trouble the 5.45 round is, MrGunsNGear did a quick gel-block test using a Krinkov.
I can see why they were called poison bullets. Nasty little things tumble well within 12″ of a gel block!