I use MAG mags and haven't had any trouble with them. I simply maintain them like everyone else is telling you here (Super important: Don't over fill, lube once in a while use quality BBs). If you do that and they still aren't up to par, take them apart and clean them really well and make sure the spring isn't messed up. If they are brand new, you may need to break them in: Spray some silicone oil in, load the mag (not overfill), and press the tab that keeps the BBs in to completely empty it. Do this several times using those same BBs (making sure they don't pick up any dirt or dust) so that the oil gets pushed all the way through the mag. Do these and you'll be golden.