Airsoft, although safer, should still be treated with similar respect as a firearm. They can cause harm to yourself and to others if not used properly. Only those who are responsible and have good intentions should be allowed to participate in anything involving airsoft.
I have spent many years researching, designing, building and testing many forms of pneumatic projectiles including airsoft and spudguns. I am no expert, but I do know my way around the block.
with that said....
The following will show my latest creation.
Step 1: The Pneumatic System
All pneumatic fittings and valves used are machined in a factory, are made of brass, steel, aluminum etc, and are rated well above what they are operated at.
This gun works by:
1. charging a main tank to a high pressure, I have used 120psi thus far and have no need to go higher just yet
2. operation of a direction control valve (3 way valve, 2 position) (trigger) empties a small portion on the main tank to a secondary holding unit
3. This secondary tank holds the same pressure as the main tank, however holds less volume, just enough to project the bb
4. A quick exhaust valve is operated, via the direction control valve, to empty the secondary tank through the barrel
The only modifications done are to make the operation of components easier mechanically and to integrate into the gun.