If you're familiar with the controls for call of duty, this would mean their right thumb was holding down the B button AND moving the right thumb stick while firing.
I'm sure there's some kind of finger yoga you can do to accomplish this, but that's hard and probably leads to arthritis. :)
It'd be MUCH better if there was an additional button on the back of the controller where your middle or ring fingers hang out doing nothing to improve your game while the rest of your fingers are hard at work.
This instructable is generic, and is also good for Battlefield players who want to press BACK to spot without moving your fingers.
NOTE: You WILL need to solder for this mod!
Step 1: Open your controller
To do this the right way, you'll need a torx t-8 security screwdriver. Or you can jam a micro flat head in on the side of the security nub and unscrew it until the security nub breaks off (like all of mine did) and then use a regular T-8 torx screwdriver.
Make sure you get the one in the middle under the battery pack and behind the sticker.
Step 2: Take it apart, but don't lose the pieces!
There are two rubbery button pads that make the connection to the circuit board behind the buttons. The D pad one is pretty well attached to the top half of the shell, but the "ABYX back power start" one is kind of loose, and will flop out if you let it. (It's not pictured below)
All the buttons will fall out if the front is held upside down, so make sure they don't fall and roll under the refrigerator. Each button has funky nubs on them to make sure they can only be put in to the controller one way, so don't worry about spinning them around to make sure they're turned the right way.
When pulling the pieces apart, the vibration motors will come out attached to the circuit board. It's not good to let them dangle from their connectors, so make sure they're supported, or just unplug them (pull straight out, perpendicular to the circuit board) and set them aside.
Step 3: Make your connections
1. Identify the button you want to move. I chose the B button.
2. Locate the pads for this button.
Your xbox controller may differ from mine slightly, but it will have pads that the buttons connect when you press them. Each button has two pads mounted on the circuit board. When that black bit on the back of the rubbery button pad presses down, it conducts electricity across these two pads, and the controller registers a button press. We're going to attach to these two pads, and make a different button that connects these leads and makes the xbox think the normal button has been pressed.
3. Expose metal on the two pads for the button.
The pads we need to short have a conductive material coating them so the black bits on the rubbery button pad make a good connection. The problem with this coating is that it's not good for soldering onto. We need to get down to the metal under this material, and get a bit of solder onto it.
The best way to do this is to take a small knife, and scrape a corner of the pad until you remove enough of the conductive material that you can see metal shining when you hold it under light. We want about half a millimeter by half a millimeter square to get good heat and solder onto the lead.
Don't worry about destroying your controller, you've got the whole pad for the button to use, so as long as you don't scrape off a large portion of it, you'll be able to wuss out, and forget this project without any impact on the controller's original function.
Just remember to GO SLOWLY. Scrape off a small amount at a time, wipe it with your finger, look for metal, and scrape some more. You only need a small area to solder onto, so don't get carried away, and don't scrape so hard that you go through the metal!
4. Solder onto the exposed metal.
With your soldering iron nice and hot, and your circuit board in a stable position, place the very tip of your soldering iron right onto the metal you exposed for a couple seconds, then lift, and inspect the area. You may see gunk covering the metal, this is the coating that covers the circuit board melting. It protects the leads from being shorted, but gets all melty when you heat it up. Wipe it away with a paper towel if you can, but if it keeps hardening before you can, try to wipe it away from your metal contact point with the tip of the iron (wiping it on your cleaning sponge often to keep it clean), or let the blobs of gunk harden, then scrape them away from your contact point with your knife. If you do NOT have gunk in the way after heating the metal, you probably picked a good spot to solder.
After you have heated the metal point, and can still see it after removing your iron, place some solder on the metal point, and press your iron down onto them both for a second or so. When you lift your iron you should see the solder covering the metal point you exposed. If you do not see this, or you see solder pooling around the metal point or refusing to let go of your iron, check your metal contact point again to make sure there isn't any gunk on it, and that you've actually made it down to the metal.
You need good metal on metal contact to heat the pad so it will bond with the solder.
Once you think you have a good connection, you can test it by placing the circuit board into the back half of the controller, attaching the battery pack, placing the ABYX rubber button pad over the circuit board, and turning on the controller and xbox by pressing the xbox button on the rubber pad. Once the controller and xbox are on, go to a place where you can test your button, then remove the rubber pad, and touch the two solder points using needle nosed pliers (making sure to touch the solder points NOT the black conductive pad. To test this further, you can solder some test wires to it, then connect the wires to see if it registers the button press.
Step 4: Add your new button!
I'm not going to lie here. This part's a little janky.
You need to drill a hole into the body of your controller that is comfortable for your intended finger to press on the outside, while choosing an area on the inside that has enough room for your button with the circuit board, motors, and motor housing (on the top side of the controller) in place.
My button was a little large on the inside, and I had to remove the vibration motor connector, and solder the motor straight to the board. This gave my button enough room to fit where I wanted it. I might recommend this modification anyway since it's easy and frees up lots of space in the intended area.
ALWAYS start with a smaller hole than you need, then step up slowly to the size that you want.
Step 5: Run your wires
We're very happy Microsoft used a rubber pad for the button contact points. It means there are no springs to get in our way, and that they will work with a wire or two running under them. Still, you want to disturb the rubber pad a little as possible, so try to run your wires to the solder points from the nearest edge of the pad.
Because these solder points are rather small, I recommend soldering the wires to circuit board last. Figure our how you're going to run your wires, cut them to size, solder the connections to the button first, then when the circuit board is back in the back half of the controller, solder your wires to your button connection points, trying to keep them as flat as possible.
Don't forget the D pad contacts have a rubber pad that goes over them, so don't run your wires over this area unless you want you D pad to suck more than it already does.
Once your connection is in place, put the ABYX rubber pad over the circuit board, pop in the battery pack, and turn on your controller and xbox to test your new button. Make sure you press the button on the rubber pad a few times to make sure the regular button presses aren't going to press your solder connection loose. Good solder connections should easily be strong enough to withstand the button pad dropping on them, but test now before you put the whole thing back together!
Step 6: Put your controller back together
Don't turn the controller so the ABYX buttons fall out, and make sure your motors don't get stuck against the motor housing, and you'll be fine.
If you're close to closing the controller, but the last bit just won't go, look at the ABYX buttons, and make sure they're all at the same depth. If they come loose and turn around, they won't slide into their housing and the controller won't snap together.
If it feels a little "mushy" on that final fraction of an inch, check your thumbsticks to make sure they're not caught on the edge of the holes in the front of the controller.
DON'T FORCE IT!
IF IT'S NOT SNAPPING TOGETHER EASILY, SOMETHING IS IN THE WAY!