I am an avid USPSA and Steel challenge shooter, I recently purchased a glock 35 M.O.S. Because I already had gen 3 magazines set up with extensions already I just used those for a few months. I started having a feed problem with one of them so I decided I would swap the 3's in for the new gen 4's. I carry a total of five mags on my belt an three were the new gen 4 and 2 were my old gen 3. Every new gen 4 immediately fell out with the first shot. Ran my old gen 3's and had no issues at all. I have made no modifications to the mag release, I have not swapped it around. Looking closely at the ridges on the gen 4 all i can think of is they are not milled enough for the release to fully engage the magazine during the cycling of the weapon. I slapped them in then pulled to be sure they were set, then bang first shot and out it came. This is a profound issue that needs to corrected. My suggestion to you would be to get your hands on a Gen 3 magazine and run the same test I did. There is a clear issue with magazines falling out on Gen 4 gunsI have a Glock 19 gen 4. Everytime I shoot it the mag falls out. Tried 3 diff mags plus 2 30rd mag. All fall out with one shot. Help do not now what to do. It is for my wife but can't have this.