I've tried several different entries from 63 to 65 and the error message remains. Changed all variables to metric, then imperial and still it remains. I did finally get to fire the gun for the first time over my chronograph and compare numbers with GRT.
GRT predicted 1790 fps and 3600 psi
Measured actual velocity was 1,500 fps and pressure too low to fireform to a sharp shoulder.
Changing effective barrel cross section between anything reasonable could not bring the numbers to agree. I'm working on every variable to make sure the parameters are accurate.
