So I made up some dummy rounds real quick just to test loading and feeding reliability in my G20. I loaded right at SAAMI spec 1.260" for 10mm and I was only able to get 14/15 into the mag. They all fed fine cycling the slide.
Recovering the ejected rounds, the thin rim of the shsllow hp held up fine and showed no signs of deformation in spite of my very soft alloy. The very tip of the rim showed abrasion from riding the front wall of the magazine.
I'm thinking this boolit is best loaded to 1.250" for best reliability. That's not to shabby considering during the design phase we knew we were bumping right up against the maximum meplate size for the G20. Looks to me like we nailed it right on the money.
I'll test 40sw in the G23 later today.