crappy brass also has something to do with pressures and what's safe and not.
True, but there may be different reasons.
The brass acts as a gasket. If the gasket is soft or weak it will show pressure signs and wear out well below the level that would stress the pressure vessel (gun). But if you get a tough enough gasket you can run the vessel through pressure cycles that will fatigue it without blowing gaskets all the time. Integrate enough fatigue and the vessel itself can let go.
