while the info above is correct - I've always been told to not worry about the difference in any modern firearm that was built in the last decade or so. Now-a-days even your .223 bolt guns, while stamped .223, will handle the extra pressure from a 5.56. If you are really worried, try it, look for any pressure signs - but if your bolt gun was made in the mid 90's or newer you probably don't have to worry about it.
I've (and many others) been shooting 5.56 through .223 bolt guns for years with no issues...
I've (and many others) been shooting 5.56 through .223 bolt guns for years with no issues...