In 2004, the mag release was redesigned. If your gun is pre-2004 you have an old style mag release and I recommend replacing it with the newer design.

Why should I replace my old mag release ?

It allows the magazine to sit higher in the frame which puts the next cartridge in the magazine closer to the feedramp. This means much smoother feeding and less chances of nose dives. This is not a fix for nose dives per se, since they typically can be traced back to incorrectly re-sized brass. For 40 S&W, shooting Jacketed Hollow Point or a Flat Nose bullet with a large flat front surface, there is less curved side surface to hit the feedramp as the slide tries to feed the next round into chamber.

How do I know what mag release my gun has ?

An easy way to find out if you have the old style mag release is to figure out how mag sits in the frame. If the magazine rattles up and down and there is quite a bit of play you probably have the old style. It's easier to feel this when you've taken the upper off. Of course you could always disassemble and check the catch itself, ref picture on the right. It'll show you how different the mag "catch" is and might give you an idea of the advantages of the new design.

Get it Here.