TK Moon Clips - I'd posted that I ordered some...
And they have arrived. They are even better than described. Completely resolved the 40 S&W issue in the GP100.
More importantly, it opens the door for a Reeder 10mm Magnum Double Action. These heavy duty clips will allow the use of 10mm Auto and 40 S&W in the same gun.
The 10mm Magnum with these heavy moon clips will be the 401 Power Mag without the hassle.