While the design of the gun is non conventional I agree it was not the gun. At over 85,000psi a Barret may have left you with a bolt in your forehead. That heavy cap threaded on with the heavy threads should have been able to take any reasonably pressure.

He said the manufacture said it would take over 85,000 PSI and I believe that. Look at high pressure hydraulic piping sometime. It would not be hard to pressure test a set of treads like that to determine when they would fail. The manufacture probably did at some point in the design. A blind hole in a piece of that steels round stock with the open end threaded with those threads and that cap, a gauge and port installed in the firing pin hole and a high pressure pump and go to pumping until it let go.

A very old duplex powder that changed it own property or someones concoction is what I suspect.

I met a guy at a gun show who had a blown up single shot bolt action style 50BMG. He had also been pretty severely injured.

An 85,000 PSI round in a Winchester model 70 30-06 might become real evil. Given enough pressure it would rip the bolt lugs right off.

Notice the chamber itself did not fail.