Hello again 4seventy,

I have just read the section on page 9 dealing with the German 16 gauge shotgun and have the book open to that page.
The author references the Standard Directory of Proof Marks as stating the action was made in East Germany after 1950 and was proofed at 13,000+ psi. He plugged that pressure into the formula using the .819 head diameter and found the pressure against the standing breech to be 10,530 pounds during proofing.

It seems to me the error you referenced being in Edition 1 was corrected in Edition 2. At least I can not find the error in Edition 2.

Thank you for pointing out the Edition 1 error and helping me to check Edition 2 for the error.

For what it is worth, I have read this Edition 2 of this book more than once and found it to be well written and very well proofed with respect to grammar and spelling. After working with you on this issue, I am given hope that it was also well proofed with respect to technical content.

Thanks again and Best Regards.
CRS