Jerry, this is not intended to be an argument. But my results came from using Pressure Trace.Google that and from the explanation on that site you will see from whence I am coming.When I started 7 years ago, I spoke with the Armusa rep. and ordered 4 types of their 12 ga. shells.They told me of their pressure measurements and when I tested with my gun,I got very close results +/- 100 psi. or so as I remember.However, that data was lost when the laptop crashed.