Oh stop - I know THAT, but ammo is not interchangeable, so why do they note them together as if they were?
Well, yes they are interchangable...The military ball ammo (5.56) just creates a higher chamber pressure and could cause jamming...But they ARE interchangable... .
.223 in a 5.56 chamber is fine. Otherway around could cause problems because of chamber pressure and slight dimensional differences.