SpudFiles

Ye its me noob, i am wanted to build the simple multishot airsoft gun with qev, And when i was searching youtube i found this and i make something similar to this and like always for me it dont work xD It shoot but it use all air in chamber . What can be the problem? (Slide valve is here beacuse i am lazy and i dont wanna to unscrew it )

Swan Donovan has a good multi shot system.

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I made that system back when I was a teen
For it to work you need a piston that has spring in the back and allows to be filled from chamber side.
If your QEV is bought un modified, take a 1mm wire and poke a hole in the piston (not in the middle or you get leaks, poke it where the thick rubber meets with the rubber skirt), then add a weak spring behind it. Then it should work.

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Ok thanks a lot guys , i have one more question. Will that work with normal compressor blowgun ? but shrader valve will be on the end of blowgun

I came up with a similar design too as my first "semi auto".
The idea is to limit the exhaust volume so the QEV would close. I made a check valve with tiny leaks instead of the shrader so I don't have to manually reset the shrader.
Basically one side of the blowgun connects to the QEV the other side has to have a valve, be it a shrader, ball valve or check valve. You can play with the exhaust volume too for different output power from the QEV

So it will work? and i dont need any spring then?

You still need it.

but no hole in piston?

You still need the hole too.
The QEV need modification in all cases, except when you're using a 3 way/slide valve setup.

Another question, I want to make hole and add spring but i want too to shoot one shot with this? Will hole and spring deacrese power with one shot? With spring and hole can i fill the chamber from pilot port? or only from chamber port?