Tippmann did not design an easy way to attach a regulator or expansion chamber to their model 98 paintball gun. In order to attach either of these devices you need to install a vertical adapter. Installing a vertical adapter may sound tricky but actually will go in very easily.
1. Purchase a vertical adapter kit for your Tippmann model 98 paintball gun.
2. Remove all air sources and paintballs from the gun.
3. Take off the hopper and elbow as well as the barrel.
4. Hold the cocking knob and pull the trigger. Allow the knob to slide forward slowly to un-cock the gun.
5. Use an allen wrench to remove the two screws on the bottom of the gun holding the ASA in place.
6. Unscrew the two grip screws holding the left grip and then remove the six body screws. This will allow the two body halves to slide apart.
7. Notice the two screws in the middle of the right body half near where the valve is, remove these two screws then pull the valve out from the body.
8. Unhook the braided stainless steel line from the valve using a wrench.
9. Wrap pipe sealing tape around the vertical adapters connection and screw it into the valve.
10. Place the valve with the vertical adapter connected to it into the gun, and replace the two screws that hold the valve in place.
11. Close the marker in the reverse order it was disassembled.