Here's a sample trace of 5 shots from a 7 STW.
The pressure readings were very consistant between the 5 shots. The narrative from the device maker is below the chart.
This interesting pressure trace was taken while shooting factory ammo. It was surely tested using standard SAMI protocols but if the lab used a peak capture meter, not an oscilloscope, they would not have seen the severe secondary pressure "if" it occurred in their test barrel.
The exit time markers are where they should be for a standard barrel. Secondary pressure events are typically less severe and INSIDE the end of a long barrel. (See tech article.)
We believe this to be a gross example of "deflagration" or unburned powder burning AFTER the bullet exits. The scary bit is more than 81,000 PSI is read by the strain gage located over the chamber! It is impossible to know if the entire length of the barrel was exposed to this pressure. But if it was, then the load is approaching the yield strength of thinner parts of the barrel and "could" expand the bore.
Ironically the exit timing, velocity S.D. and accuracy was great for factory ammo... but it does light up half the county when fired at night.
