Guns & Ammo Question

Here is a letter I sent to the editor of Guns & Ammo regarding an article about caliber calculations. The author's calculations for 9mm and below are more than what I was calculating manually. We'll see what the response is.

Mauser’s Metrics?

I was not able to duplicate the Mauser’s Metrics  calculations of Craig Boddington in the January issue of Guns & Ammo.

Based on my calculations, I get the following:

6.5mm = 0.256
7mm = 0.276
8mm = 0.315
9mm = 0.354
9.3mm = 0.366
9.5mm = 0.374
10.75mm = 0.423

Am I missing something?