Since I only have 2 mags for my new M&P 9 Pro I've been looking for more mags everywhere. Finally heard about a store having them locally today at a match. Bought 4, got home, and then noticed that they're ProMag brand. I put each one in and hit the mag release button, 3 out of the 4 wouldn't drop free, I had to manually remove them and one dropped so fast it hit the floor and the spring came out - pieces flying everywhere! What brand mags are best to use? Obviously, I need something that will drop out when I hit the button.