*Edited to add that most of you probably don't want to read a novel. Just look at the pictures. The simple scientific explanation of the thumbs forward grip is that you are directly counteracting the axes of movement of the gun with opposing force. Not simply gripping the gun, but applying opposing force in the exact opposite direction of the recoil path and corresponding movement of the gun in recoil. The modern grip method goes by several names, but is typically referred to as the thumbs forward grip. It consists of the support hand wrist cammed forward and the thumb pointed forward. There are MANY variations on this. Then there is the aggressive version of the thumbs forward. This consists of the support hand wrist cammed all the way forward, which typically positions the thumb pointing straight forward. In this position, if you take your support hand off the gun and open your fingers outward, they will typically be pointing towards the ground at a ~45 degree angle, with the thumb pointing downrange. A golden nugget is, to simply do that. Cam your support wrist all the way forward, thumb pointed at the target, then bring the hand back to the gun in that position, and you should be very close to the final position you want to be to achieve an aggressive thumbs forward grip. So why does this matter? In the grand scheme of things, for most people's uses, it probably doesn't matter a whole lot. If you are interested in extracting maximum performance out of your gun, especially shooting at speed, excelling in competition, and generally becoming as proficient as possible with your pistol skills, it might matter a bit more. Lets first take a look at a typical thumbs forward grip, as performed by most people when they are new to this grip method: Grip-2 by Dillo Dynamics, on Flickr In the grand scheme of things, I'll throw out an arbitrary number and say this grip probably achieves 80% of the recoil control and consistency you want in a two hand pistol grip method. You are getting a significant portion of both hands on the gun, and relatively high on the gun. For many shooters, the focus here is on front to back pressure with the gun hand, and side to side pressure with the support hand. I referred to this as circular direction of muscular skeletal energy, as you are putting the energy out, into, and wrapped around the gun. Some of my terminology may not be 100% scientifically correct, but I'm sure you get my point. Here's the bigger picture of what's going on with the casual thumbs forward grip: Grip-4 by Dillo Dynamics, on Flickr As you can see, the shooter is relatively high on the gun with both hands, has a decent amount of both hands contacting as much of the gun as possible in this position, etc. One thing that stands out, however, is that there is nothing really substantially resisting muzzle flip in the opposite direction on that axis. Again, not bad. Most of the way there, but there's still some performance to be had if we tweak it. So lets take a look at an aggressive thumbs forward grip. As always, there are variations. Look at some of the leading world class IPSC shooters and you will see lots of little variations on many of these aspects of grip. That's normal, as human physiology is infinitely variable, so everyone's ideal method for extracting maximum performance is going to be a little bit different from someone else. Lets focus on some simple factors that are relatively universal: Grip-1 by Dillo Dynamics, on Flickr For most people, this won't look like a massive difference, and again, in the grand scheme of things it may not be for some people's needs. The differences we do see are a more extreme camming forward of the support wrist. Between this and the first picture above, there is roughly a 27 degree difference in wrist angle. By camming the wrist farther forward, this also has the effect of bringing a majority of the base of the support hand (palm and thumb) higher up on the grip. In fact, in this case the thumb and base of the palm are nearly inline with the bore axis and are on or just above the top of the frame. The higher you can get in relation to the bore axis, the more you can counteract the fulcrum point created by the web of your gun hand. So by default, this will reduce muzzle flip even further than the casual thumbs forward as it is geometrically superior. Interesting things to note are the path of camming the support wrist forward is basically the exact opposite direction of the path of muzzle flip. This, in effect, creates a lever out of the support hand, which is actively camming down to resist the opposing motion of the gun in muzzle flip. Simple geometry. I'll get to the skeletal muscular energy thing here in a bit. . Grip-3 by Dillo Dynamics, on Flickr So we've already seen that the camming action of the support hand provides a direct and opposing resistance along the X axis (muzzle flip). So at a minimum, we have one aspect of grip opposing movement in that axis. With the casual thumbs forward, there are no discernible or significant forces acting on or resisting this axis of movement. +1 for aggressive thumbs forward, if you want that extra performance. For many, not a big deal either way, and that's fine. Another thing worth noting is there are several other small factors that can be used to your advantage, to gain another few percent in managing recoil more effectively and consistently. First is with the gun hand. Many people, when new, simply squeeze the entire gun hand like they're squeezing a baseball bat. This can have some undesired performance issues that can lead to thrown shots or inconsistency of shots. For example, if your fingers are long and your fingertips are resting on the side of the grip panel instead of the front strap, if you squeeze from your fingertips, this can cause the gun to torque to the side under recoil, and probably several other potential issues. Once people progress past this point, they learn to instead think of the gun hand as a c-clamp, squeezing more from the intermediate or proximal phalanges (middle of the fingers - Front) and the palm (Back). This creates even front to back pressure, and no unwanted side or angled pressure. Moving beyond this intermediate level of gun hand grip, there are some additional factors that can help gain you some more performance and consistency. With the gun hand, think of torquing or camming the four fingers of the hand opposite of the thumb. When gripping the gun, think of camming or pulling the four fingers not only straight to the rear, but also downwards, and using this leverage to force the web of the hand upwards into the grip arch. You are now both pushing and pulling on the X axis, so an additional two factors working to counteract muzzle flip. The next element of grip is the support hand. As with the gun hand, we want to apply force into the gun on an opposing axis to the gun hand. Basically side to side grip pressure. With the aggressive thumbs forward grip, I like to think of clamping the very base of my palm (specifically the median nerve, palmar branch or the Adductor pollicis muscle) into the highest part of the grip/frame that I can reach while still allowing proper function of the gun (no inadvertent slide locks from this muscle resting on the lever). Where some extra performance can be gained is in clamping the base of the palm into the gun with almost a slight downward pull, and correspondingly pressing the support thumb into the frame, and if possible, pressing slightly downward. In the case of Glocks or other guns where the frame is wider than the slide, there is usually a ledge where you can achieve this. You now have two further factors providing resistance on the X axis against muzzle flip. The big picture to think about here is where is that skeletal muscular energy going? You're putting it out there, into the gun, but is that where it should stop? If you only get that energy to the gun, you are in effect simply trying to hold the gun in place without necessarily resisting the rotational force of the gun. If you instead think of putting all of that energy out there and basically "pushing past the gun", putting that energy into a direction that is going to counteract muzzle flip, then you stand to gain a lot of performance. Anyways, that's about enough out of me tonight. As hard as I try, it always ends up as a wall of text.