So I bought 6 of the mag extension packs and mated them with the current generation of Glock 21 mag. I was told that they were supposed to work in the G-30 as well as the G-21. I have a stock G-30, which is NOT a short frame. I was told these would not work with any short frame model. They all, universally, jammed more than once. It was always a failure to feed malfunction where the slide went over the top of the cartridge in the rear, erecting it so it wedged in the top of the chamber. This was with quality hollow point duty ammunition as well as with practice ammo. I tried again with a different recoil spring set up in case there was a timing issue. I used the Wolff set up that was +2 pounds, non captured, dual spring. This seemed to decrease the incidents of malfunction but 4 of the 6 had 3 or more malfunctions. So can people experienced with this product please advise me. Does this product only work with the G-21? (Aside from the Kriss machine guns) Is it an issue where it works in latest gen pistols but not early ones? Do I need to use some sort of magazine adapter collar or sleeve to align it properly? Is there something simple I am missing but you found in your experience with this product? This is not intended to be a flame thread, but rather one of advice. Please feel free to PM me instead of posting negative comments regarding this product so we can keep with the positive nature of this forum. Thank you.