Well the way I understand it is this way. Look at your barrel they normally stamp the chamber on it. so if it states something like .223 and nato 5.56, .223-5.56 or .223 and nato 5.56 your good to go. If they have .223 and nothing else then take caution cause it is not designed to fire the hotter load. I know there are some out there that say it is okay. you know they call him “lucky” or old “3 fingers” or “lefty” or “righty” whatever cute name they give the morons that ignore manufacture specs. Anyway there are also rifles that may not have it stamped such as the Ruger mini-14, then check with the manufacture and it is designed to handle this hotter round. However, as always I recommend that you do you own research and don’t just take mine nor “lucky 3 fingers” word for it. So that s the short version of it, and here is the long-winded version of it. Amazing, someone has a longer winded version than me? I know, Right? Her it is copied straight from the pages of the cheaper than dirt website. Read full article here.