Kjw M9 question

[Renek]

I have a Kjw m9(not the full metal, still has a plastic slide and barrel...at least until saturday...), have had this gun for almost two years, and its seen a good bit of use. All parts are still stock. My problem is that whenever I fire the gun, the mag falls out. I dont have any problems if I hold the gun with two hands(which most the time I would do anyway). However, its bothersome, and the mag has taken one or two hits to the concrete because of it. Any help would be appreciated!