I am planning on building my own homemade. I went to homedepot and looked around for a ideal trigger. I thought about ball valves, but they are too slow. I thought about hose sprayer handles but they won't make a good enough seal. I then asked my dad about my problem. He told me to look at blow gun triggers. What i mean by blowguns is the kind of valves used for air compressor/blower deal. This would be the idea trigger for the gun. It is call Blowgun safety lever.
building wouldnt really be too hard and you could save on buying a solenoid because you would only really have to buy a ball valvebecause it wuld be a matter of opening up the valve and pointing and letting loose on the enemy :sinister:
The only draw back to this is that you need to figure out how to connect the airsupply sorce to the gun. But it would be easy to use.