Jesse, the Mini 14's barrel is "Stamped" 5.56 NATO as pictured and will fire both 5.56 & .223 no problem. google.com/search?q=ruger+mini+14+caliber+stamp&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjbksqo3LnaAhUknuAKHZDJAc4Q_AUICygC&biw=1280&bih=618#imgrc=kK9kz9
