We agree that Glock builds a solid firearm, but when was the last time you heard someone pick up a Glock and say, 'This fits my hand like a glove!' Glock was kind enough however to leave more material on there than was needed, so we can easily shape and re-build that Glock to actually fit your hand.
Glocks are plastic. There, I said it. That means that they are incredibly durable and resilient, but when your hands start to get wet, they get slippery. Yeah, they've added texture over the years, but most people still feel it's not enough. Some folks will use grip tape, and that is very aggressive, but it can peel off at bad times, leaving a sticky mess. It also adds to the grip size on a firearm, already known for having a huge grip. We actually peel off the factory texturing and then stipple the underlying plastic, so your grip will be slightly smaller than factory, rather than slightly larger. We use a multipoint stippling which works very well, and replicates grip tape quite nicely. We've experimented with a lot of different textures over the years, and we have settled on one which is more aggressive than most stippling, but maybe slightly less aggressive than the harsher grip tapes. The beauty of that is you can carry and shoot the gun, and as/if you identify areas which are to aggressive, you can hit those spots lightly with 400 grit sandpaper, while keeping other areas more sticky, and custom tune your grip to your hand and carry rig.
If you happen to have a hand that fits the factory grooves, great! If you're like the other 98% of the population however, it sucks that you have to get your hand on the grip exactly right in order to hang on to it. By removing the finger grooves (with stippling) you can snatch that firearm from the holster and where ever your hand lands, it sticks and you can go. Of course it's better to get a high perfect grip, but we all know in the real world that you need to take what you can get and make it work. Most people feel that removing the finger grooves and a good stipple make that job much easier. However, we can easily leave the finger grooves and stipple right over them if you would prefer that.
When the gun goes off the slide is going to rocket back and smack into its stops, dumping the residual energy into the frame. If you are hanging on by the bottom of the grip, it's going to be super hard to control muzzle flip. The higher you can get your hand on the grip of the gun, the more 'flat' the gun is going to shoot. Put another way, if you could get your hand right behind the slide, there would be no muzzle flip; the gun would just recoil straight into your hand. Obviously we can do that, but we want to work on getting as high as possible. The trigger undercut helps you do that, by allowing the middle finger of your strong hand to come up farther on the front strap. If you picture it, that also helps straighten out your rest, and decreases the angle your trigger finger has to make to reach the trigger. This is probably one of the most subtle modifications we do, but it actually has one of the biggest effects for shooting. This, in conjunction with the finger groove removal and stippling completely changes the feel of your firearm.
Index Points/Gas Pedals
The thought process behind index points is somewhat complicated. True index points, just stippling patches above the trigger on both sides, gives your trigger finger somewhere to land when you aren't shooting. But beyond that I don't see them making a ton of difference. Also if you have a tight fitting holster, or even worse a nice leather lined one like Safariland, those index points are essentially increasing the width of the firearm and will bind like crazy in those holsters. Just a word of caution, but for some people they are absolutely the correct option. Some folks don't run anything there, and that also works fine. The last option is the 'gas pedals,' or 'accelerator cuts.' Basically these are cuts angled into the frame above the trigger. If you've got a good grip on the firearm, and especially if you're shooting with your index finger around the trigger guard, you can actually almost grip the front of the frame with your support hand, dramatically reducing muzzle flip. Is this a universal? Not at all. But if that fits your shooting style, its a solid upgrade. When we do this, we cut away material and then stipple inside that area we've cut away. So the outside dimension of the frame remains exactly the same, circumventing any holster issues.