Thank you all for the feedback
You've inspired me! Now I have no choice but to make one. Thanks a lot...
The parts are available from any hobby shop, and I didn't use any complicated tools - mostly a hacksaw, sandpaper, and an electric drill clamped in a vice as an improvised lathe
Hope you don't get lead poisoning from having lead pellets all over your house.
Thats mostly a risk from handling the pellets, I always wash my hands after

Besides, the impact energies aren't sufficient to give off too much dust.
I'm using a presta in mine at 240psi and I'm likely to be using it at 300psi too when I get hold of the right kind of pump.
What are you using to get 400psi?
Good to know, though I think I'll stay with the schrader for this one, don't feel like hacking it up. This is the pump I have:
the 400 psi figure is assumed, gauge only reads till 300 (for spartaaa!) but I keep on pumping until the needle hits the stop (see attachment)
I can't BELIEVE you were able to fiddle around with such small parts! I get annoyed having to fix my 1" porting piston valves
Don't try
making a check valve out of lighter bits then
Will it shoot through cardboard? plastic? kevlar?
At 200 psi, it won't make it through a top of a pizza box. However, for such a small chamber, short barrel and tiny projectile, I wasn't expecting much better. Still waiting for the courage to take it to 400 psi again though hehe