I'm of the opinion that if I don't know and trust the person reloading my rounds, then no! He stated they were very old and had been through other owners. Chain of custody is important.would it have been safe in another type of .50BMG rifle?
I doubt it would have gone any differently in any other rifle. His friend thinks that pressure at time of firing was 85k psi due to the stripped thread on the cap. I don't think any rifle could be expected to contain that much pressure.