Seeing a lot of hate for Serbu here. It was not the rifles fault. The threads of the end cap of an RN50 rifle are rated to withstand firing pressures up to 65,000 psi. The way the end cap sheared off the receiver would have to have been 85,000-90,000 psi. The round either A:had a double charge, or B: unstable powder due to being my age.
Mark Serbu released a brief on it, Ian Mccollum of forgotten weapons did a 30 minute video on it.
Ian’s take was great.