This is a minor modification to the Kipkay’s Paintball LAW design (https://www.youtube.com/watch?v=jsXd8yu9wq8). It makes the LAW easier to assemble and more sturdy.
In addition to all the parts listed in the Kipkay video, you will also need a 2″ PVC coupler, a 2″ to 1/2″ PVC bushing, and another 1/2″ galvanized pipe male-female elbow. The complete parts list is:
-2′ of 2″ PVC
-2″ PVC slip-slip coupler
-2″ slip to 1/2″ pipe bushing
-1/2″ pipe male-male nipple (1″ works well)
-TWO 90 degree male-female 1/2″ pipe elbows
-1/2″ female-female ball valve
-5″ of male-male 1/2″ pipe
-1/2″ female-female coupler
-Teflon tape
Use 5″ of 1/2″ pipe as your expansion chamber, as suggested in the Kipkay design. According to this handy air tank calculator spreadsheet (found at http://www.spudfiles.com/pneumatic-cannons/topic20193.html), to get maximum effectiveness out of your 12g CO2 cartage, you will need a lot more than a few inches of 1/2″ pipe. Due to the properties of compressed CO2, you would need 40 inches of 1/2″ pipe to get 500psi in your expansion chamber, and over 200 inches of pipe to get to 100 psi. Since that would be hard to run around with, 5″ of 1/2″ pipe is a compromise that works well enough.
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