4seventy,
Thank you. I have recalculated the pressure numbers for both my double rifles made on shotgun actions and all seems OK. For instance, the Beretta 12 gauge factory proof pressure was stated to have been 17,000 psi.

In a day or two, I will have time to revisit that section of the edition two and look for the error you mention. I hope it was corrected, but shall check and advise.

Thanks again.