Every gun is different, but you should be able to get to the internals by popping out pins and screws that keep the body halves together. Make sure you keep the screws.

Once the body is separated, you should see a large metal piece that would have some wires running into it. This piece is the gearbox.
There may be some screws holding the gearbox down, if so you can remove them.
Remove the gearbox from the gun by lifting the gearbox and the motor (a cube like structure likely located in the pistol grip). Set them aside and move the body out of the way.;
, You can open the gearbox by removing screws keeping the halves of the gearbox intact. Make sure that the front of the gearbox is on your right. You can now lift up the top shell of the gearbox, which should reveal many gears and pistons., You will need a screw-driver for some of this. You will want to remove things in this order:

Spring and buffer-tube/spring-guide. Make sure you keep the buffer-tube/spring-guide.
The bevel gear. This is the gear the will be closest to you.
The piston system.
The other two gears.
The the trigger and trigger spring. You will need to keep these and the trigger screws for later on.
The trigger contacts and wiring.
Anything else left in the gearbox.
 Using the trigger screws you removed, place the trigger board where the trigger contacts once were, and screw it in., Take the main module and place it where the piston once was, making sure the notches on the gear box and main module are aligned., Take the wiring from the main module and plug it in to the trigger board., Take the wiring harness and snap it into the trigger board., The tub should be run down the pistol grip area of the gearbox., The wiring harness will follow the path of the cables going to the battery that were removed., Put it back in just as you removed it. Place the trigger over the trigger spring. Make sure that the trigger and trigger spring are aligned correctly., Make sure it is facing toward the main HPA unit., Put the other half of the gearbox back on, make sure nothing is getting pinched, and screw the halves back together., You can now close the gun, and you are finished.
Remove the gearbox from the gun.
Open the gearbox.
Gut the Gearbox.
Install the trigger board.
Install the main HPA module.
Connect the trigger board and the main module.
Connect the wiring harness.
Position the HPA tube.
Position the wiring harness.
Reinstall the trigger.
Reinstall the buffer tube.
Close the gearbox.
Put the gearbox back into the gun.
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