Fueling, feeding, pressurizing ... what ever.
A bike pump is simply to slow to give it the needed punch.
BTW fueling...this valve style could work on a hybrid as well ... I think.

It sounds like he is using a bike pump.
So let him get a proper fueling system and see again.

Do you have deposit bottles (PET) where you live? Where I live nearly all drinks are in these bottles, designed for multiple use out of pretty thick plastic. Once I pushed one to over 200psi without deforming itself (only for testing).

I think it's the way Hotwired said.
A balanced piston that is easy to move because there is no specific pressure on one side.

I was thinking to build a trigger like that.

The I.D. of the hose barb is 18mm but i can also get one with 25mm I.D.

@far_cry I would lie if I tell you a specific number but I'm sure it can handle more than a shockpump or a firdge compressor could provide and that's enough. @LikimysCrotchus5 Yea I know that I'm not the only one who build valves like that. I saw atleast two different people on youtube with simmilar...

@roboman The idea of that blow forward bolt is that you have a cone with big exhaust holes at the ?edge? (green) and a negative cone (blue) with a pipe in the middle. When you trigger your gun the blue part gets a hit forward before the air stream enters the pipe. I thought the shape of a cone would...

I got the parts + a 1 meter copper barrel from a friend for 20€~25$ (he is a plumber and doesn't pay VAT).

Thanks fore the kind comments, I really appreciate that.

@mark
The concept of that valve is to power a semi auto. The quick connect is only to attach the blowgun. I fill the chamber from another place, it's simply faster than pushing the pressure through a small equalization hole.

This is the way I build a high pressure self-closing piston valve (barrel sealer). min. actuation pressure: 30 psi (varies due to the used spring and piston) The parts: 1/2" quick connect (only to connect a blowgun, not to pressurize) 3/4" female to 1/2" male 1" female to 3/4" male 1" nipple (find o...

The front grip should be able to move from the left to the right of the gun.
Some people out there are left handed (me included) and it would be a nice
gimmick if you could customize it.

Visit http://www.jamendo.com
It's all music under "Creative Commons" license (for non commercial use).

I was also thinking about a blow forward bold and came up with an idea that might work without losing much performance. http://img525.imageshack.us/img525/9388/blowforwardjpg.jpg For the shape I would use a little funnel and cast it in epoxy. BTW which rings are bigger? a: blue circle b: green circle

I build on of these, bad flow but really good as a pilot valve.
You can operate them with a blow gun (piston needs a spring) due to the little pilot volume.

We will see... I'm really in the mood to build this. I rather build something by trail and error than not trying it.

And by the way...if I don't get it to work I have all the parts to build a nice pump action reloader.