I loaded the 40 into factory G20 mags, which of course fit in my G21 because the frame is the same as the G20, and other than a little sliding back and forth in the mags, of the cartridges, there appeared to be no problems. Of course these are just my results.
I am in no way warranting the use of 40 S&W in a Glock 20 or 21, it is a personal choice. Do so at your own risk.
And don't tell Gaston about it, they are kinda fussy about those things.
G29SF, G38 w/lasermax, The 21 Club #7663, The 10 Ring #7663, The Bull Dawgs Club #7663, US Army Veteran
Amateur Glock Modification Expert...
Last edited by vaquero aleman; 01-21-2013 at 10:56..