I just inherited my fathers guns and reloading equipment. I learned reloading some 30 years ago, but haven't done much of anything since. One of the rifles is a Rugger M77 is .223 Remington. I have been talking to several friends who have told me that with a bolt action rifle you can't (or shouldn't) use 5.56 NATO rounds. My problem is I have been looking through the brass he had, and there are quite a few different brands. How do I tell which shells are .223, and which are 5.56? Any help would be very much appreciated, as my search on the web has been fruitless.