I finished my new launcher for the season. All told it cost me around $60 to build. Around $30 of that cost was the pressure washer handle that I bought from Tractor Supply, but they can be bought in many hardware stores.
The input for the handle is plumbed down to a tippman ASA using brass gas line fittings. The fittings are rated for 1800 psi and up.
The output of the pressure handle is threaded into a steel nipple, then into a pvc clean out, into a larger pvc clean out, into a 2 inch pipe for the barrel.
There is NO air chamber. When the trigger of the pressure washer is squeezed, it fills the lines with liquid C02 which expands pushing the rocket out of the barrel. The washer handle itself is rated for 5100 psi, so there's no chance on blowing it out.
I am currently getting between 200 and 300 feet depending on winds and such. The launcher isn't very efficient, I am getting about 10-12 shots per 9oz tank. Another draw back is it MUST be a CO2 tank, no HPA. Also, it can't be an anti siphon tank. I plan on testing it with a remote line next. I believe I will have better efficiency, but less range that way.
Below are 2 videos I made today with it. I apologize for the sound, it was pretty windy out this morning, you aren't missing me say anything important though.
Let me know what you all think and if you have any questions!