It's probably the metal body. The only ones that I've found are to spec are Guarder ones and Prime Airsoft ones.
Try using a TM hicap if you have access to one. You're fucked if they work, since in my experience, on the off-spec ones, only TM hicaps and standards work. I have a DTP body on mine and it didn't work with any other mags.
Try pushing on the bottom of the mags and firing. Like push up, and hold.
You didn't tell me you had a metal body, dumbass. I wouldn'tve sold you these had I known.