Make the Air Tank-

You can make an air tank a couple of ways. #1 is you can just buy one, for like $30 on ebay (rover.ebay.com/rover/1/711-117182-37290-0/2open_in_new), or use a bulkier tank, one of those white ones.

This is how to make a air tank outta a soda bottle. I think it holds 90 psi or something like that. anyways, you can join 4 together, and yeah. You know, if you don't have a propane tank (or don't want to risk an explosion). I tried this setup, it might just be me, but i really didn't trust it, and only got up to 80 psi. There's just not enough air.

OR you can make it out of a propane tank. Try at your own risk. I did a PVC one.

I like this one the most, mainly because i can pump it up a LOT and, at schedule 40, don't have to worry about it blowing up. That's the fear, because if it blows, it blows into fragments, which, i gather, can hurt. A lot. I changed the setup for air in/out. instead of having one for both, i got flat caps, and on the top, i drilled two holes- one for the nozzle, just connected to the hose, and the other for the tubeless tire valve. I can pump it up to about 115 psi, after that i get a bit queasy.

Make the trigger/handle

You need-

1. Some form of spring loaded valve

2. rubber tubing

3. nozzle to connect to tube

you can see what i came up with below

One note on the nozzle/pipe connection- there is a tight o-ring on the nozzle under the tape

Barrel- use a piece of pvc the same size as the diameter of the dart, i don't know what that is right now. I also added a piece of pvc to the front to look as a silencer :D it looks really cool. Plus, one more thing, you can put a piece of pvc perpendicular to the barrel. You know, like a pistol grip. I'm going to leave mine flat, like a rifle. Plus, not sure how effective it is, but i added a piece of pvc, i don't know what it's from, but it makes a good scope.