ok guys, got a question, im pretty sure i know the answer to but i wanted some reassurance. while working today i happened to pass a store and a smith and wesson dealer sign caught my eye, so i stopped to see if they had any 223 in stock, well they guy says sure here ya go, and hands me boxes that say 556, and i said oh no good i got a 223, you cant shoot 556 out of it. so he asked me what kind of gun, m&p15 i said. so he says its a 556, i told him it says 223 right on the barrel not 223/556, he said i think your wrong, i knew i was right, and he said either way ALL smiths are chambered for 556 so you can shoot 556 no matter what the barrel says.... now i think thats dead wrong, if it could handle 556 it would say 556, am i wrong? my gun says 223? if this guy was wrong he definatly is giving info to people that could be potentially dangerous?