Bonehead question re: 5.56mm vs .223

[sig22018]

The civilian AR15 is chamberd for the 223 yet the military uses 5.56. What is the difference between the two rounds? I see them both on shelves in stores. A friend asked me and I did not have an answer. Which should I use in my AR that I am building?

[Mr. Beretta]

Ted beat me to it.

Bookmark that link.

Best info I've ever found on the issue!

[sig22018]

Technical Ted and Mr. Beretta

THANK YOU! That link answered my questions and alerted me to issues I did not know about. Thanks a million guys.