Barrels are proofed to 129,000psi by the factory.

Remember that a proof pressure is not the pressure that the barrel will tolerate continuously. Proof pressure and working pressures are different. All CF smokeless guns are proofed to much higher pressures than the working pressures they will tolerate indefinately as a margin for safety. With gross overloads of smokeless powder, it is very possible that Bridges gun experienced pressures over the 129,000psi proof pressure. It's also possible that repeated exposure to overloads weakened the steel and created stress fractures that eventually yielded to continued over pressure loads.

Mike