To start out unscrew all of the screws and keep them in a place where they can't get lost easily (I recommend getting a small piece of duct tape, and putting all of the screws on it.)

This is a picture of the internals the way they should look when you first open up the gun. (This should come in handy if you can't figure out how to put the gun back together.)

Pop out the barrel. Therell be an air-restrictor towards the back of the barrel. Yank it out. (You wont need it anymore.)

Shove the piece of PETG down the barrel of the gun, this might take a little work, but it will go down.

This it what it should look like now.

Hot glue the barrel to the plunger shaft.

Hot glue around the barrel also.

Next, take some electrical tape and wrap it over the place you just glued a few times. Now it should look like it does in the picture. Put the gun back together. Finally add a few rubber bands to it and youre done. I also stuck a few inches of PETG into the ammo holders so it can accommodate micros. My gun got around 85 ft.