Waw !!! thanks, but I think is too match tor me I buid this rifle just for fun, have a lot of power with paint-ball, is too more for self defense, too dangerous.

For self defense I have my lovely C3 Propane :)
https://lh3.googleusercontent.com/-ZyjAWJVPCrk/UqoRN8KZVoI/AAAAAAAAK9c/1P8q9tRw2jM ...

https://lh5.googleusercontent.com/-VMKHhjntDaA/UqoMSzO7GvI/AAAAAAAAK9I/cX1gPD3nXu0/s912/IMG_6162.JPG
https://lh3.googleusercontent.com/-lAw26ZIwAM8/UqoMRyS5niI/AAAAAAAAK84/sH2oh_1G_2I/s912/IMG_6163.JPG

You should really look into some sort of custom slugs to make full use of the power ...

The barrel looks like the real thing... recycled from a large bore muzzle loader?
Interesting pilot (or its not there yet? I see one "port" of that thing behind QEV has a suppressor (at least looks like) but then there is the blue tube...)

The gray plastic part is small QEV, the small QEV work ...

Thanks for points
I made this gun years ago.
The barrel are for paintball gun. (sniper type, I don't remember model )
I try to shut with paint-ball at 8 Bar pressure (120 psi) but the shock is to strong for paint-ball and explode in barrel, the maxim usable pressure is 6 Bar (80 psi).
The gun is ...

My sniper unfinished

https://lh3.googleusercontent.com/-6dqQB4Qr2uM/Uqi-D_XvpHI/AAAAAAAAK54/ozFW_k9DV7E/s640/IMG_6131.JPG

https://lh5.googleusercontent.com/-RNI8phl1oLM/Uqi-CajjiCI/AAAAAAAAK5w/hbcccNaCkuM/s640/IMG_6132.JPG

https://lh5.googleusercontent.com/-ORa5L4lmfV4/Uqi9-3clhQI ...

price for qiik exhaust valve size 3/4 is 7,71 Euro
and for slide valve 1/8 is 4,41 Euro

very cheap and do the good job (very fast opening)

Is very easy to use pneumatic Quik exhaust valve made by Aignep Italy
http://www.aignep.it/article/articleview/59/1/54/
And
Slide valve
http://www.aignep.it/article/articleview/60/1/54/

Best to use Quik exaust valve size 3/4
and slide valve 1/8 or 1/4

I tray with 1/4 quiq exaust valve and work ...