So since this thread has had some different things about .223 vs 5.56 my AR is stamped .223/5.56 so would it be .223 as a best bet?
.223 will fit into a Wylde or 5.56 chamber. 5.56 won't fit into a .223 chamber (safely). I've never seen a ".223/5.56" stamp, but the important thing is to make sure that its got 5.56 stamped on it (before you go putting 5.56 NATO ammo in it).