Forrest, you did not specify an item. 95% of AR barrels and even Bolt gun barrels are stamped 5.56 or 5.56/223. I would venture it is stamped 5.56 but can give you a 100% accurate answer when you select an item. Thanks.

what make and model if its stamped .223 it should not be used with 5.56

Please provide more information on the listing you're asking about so that I may provide a suitable answer. But if it is labeled 223 and not multical or 5.56 then it is most likely not rated for 5.56