After reading numerous threads and how to's I assembled two KRISS .45 acp mag extension on my G20 mags. I shot 33 rds through one and 66rds in the other (it was all I had reloaded). The function was fine I think that the weight change as the mag empties made the first mag double feed once. I call it a success and now wonder why no Glock equivalant to the Beretta Storm carbine? 10mm Carbine would be very awesome.