Here we go I imagine that you have answered this question before. Whats the real difference between them?I have heard that 5.56 is a hotter load,the primers are harder and need a harder and deeper strike, the bullets are larger diameters,the case shoulders not the same ,then my fav the head stamp aaaa! My reason for asking being I am thinking of getting a new( cal to me) rifle target model and the manufacturer states 223 only while for the same model the plane Jane. one its will take 223 and 5.56. Could you in your with infamously wisdom and tac give me a straight answer please! And while on the subject the same for 308/7.62. And you have beautiful eyes and an engaging smile ( a little gratuitous flurtation never hearts) thanks!