I just put some mil 5.56 rounds through my .223 Winchester and each one tumbled so that they hit the target side on. I know that the shoulders of the chamber are a different shape but would this distort the round sufficiently so that it's tumbling as soon as it leaves the rifle? I remember that this sometimes happened with the Armalite but back then we were always told that this round was designed to be highly unstable. Seems that I can't save money using surplus ammunition. Anyone use military 5.56 in a civvy rifle?