Check the headspace on that National Ordinance 03A3. I had one and the head space was way off and I had to get the chamber reamed out a few thousandths before I could shoot it. A round would go into the chamber, but the bolt wouldn't close. I think they were made up out of various parts at National Ordinance and they don't always go together perfectly. Great find though! I'd love to stumble onto a treasure like that!