I have 5 magazines, 4 have been used to fire 700-ish rounds. I have one new (unused) magazine and plan to go to the range tomorrow specifically to see if I have any issues with the new mag. Again, the older 4 mags have been fine since my 1st couple of range sessions. I've used a wide variety of ammo and I don't know what causes the problem, but do believe that it's mag follower/spring related. I wouldn't hesitate to contact S&W, if the problem persisted...