They found the .50 caliber slugs on the ground, under the table. They went off, in the gun, but, the cases had to be knocked out of the chamber.
I doubt anywhere near 55,000psi was generated with the sloppy way the chambers fit the .50 cal rounds. It was gutsy, and stupid. Barrels didn’t look to be 18” to me either. Gutsy, stupid, and against the law.

Best,
Ted