Hey guys, I am new to the forum & AR 15s. I have some shooting buddies that are telling me the commercial 223 ammo & 5.56mm ammo are not interchangable. Also, all the reloading info that I've found only says 223 Rem (5.56mm), which is the way that I've seen ammo packaged. What is the story here. Can I shoot commercial 223 ammo in my 5.56 AR? Also what about reloading using 223 dies and brass. Can Remington brass be fire formed to fit a 5.56 chamber.
Any help would be great.

Since I'm not an expert by any stretch of the imagination I'll give you a short answer. Yes, you can shoot .223 rounds from a 5.56 chamber. I've read that 5.56 rounds, such as Q3131A, in a 223 rifle may cause some concerns of over pressure due to the tighter chamber and the higher pressure which milsurp ammo is loaded to. I'm sure someone will be along shortly to give you a more in depth answer. Hope this helps for the time being.

.223 vs. 5.56

Is this for shooting ducks?