Okay, this is going to sound dumb and complicate the problem. I did the exact same things as gunfreak, built a piston made out of fasteners, with a neoprene washer as the sealing head, and I KNOW that my gun works with my hot glue piston. It DOESN'T work now. I have EXACTLY the same issues he has. C...

It's not an inline, made from galvanized schedule 40 steel plumbing. The way it's designed, if you don't open the pilot valve quickly enough, it just empties the chamber until it's almost empty, then the piston shoots back and you get a really whimpy discharge, that happens at about 20 psi. If you o...

I have built and am working on a pneumatic cannon with fairly low capabilities, and since it is build from schedule 40 steel and aluminum, I am now looking for some way to get over ~200 psi (low, I know) chamber pressure. I do not have ready access to a refrigerator compressor, but I am interested ...

Ah do you know how a piston valve works? It has absolutely nothing at all to do with a vacuum. Difference in area is all that it is. I'm looking at one right now, and I know how they work, or at least the one that I made. From your leak description it sounds to me like your piston is refusing to se...

Wood might work, but dowels can be fragile. Take a part that is attached to your tee out, lube that up, and pump it full of hot glue and you've got yourself a body-sealing piston, just screw your head into one end of it and point that forward. *pwhew* that was close. So you fill through the pilot, c...

Agreed. Safety is paramount.

Any ideas on the construction of a lightweight hybrid piston?

but getting a 40ish buck ac compressor of ebay it your best bet since you will only go to 200 psi

Then where did the 200 psi come from? I'm confused....

The back of the piston needs to seal, yours seems to be waaaayyyyyy heavy, which will kill the effectiveness of the gun. I would removed the spring, as this plus the weight of the piston will kill the opening speed. And it seems to me like it's possible that the piston has wiggle room inside the tee...

Really anything that's soft and can make a seal will work for a piston face, if you apply a solid nonpolar lubricant and apply enough pressure. Pump quickly, don't expect a newbie hybrid to seal at 40 or even 60 gspi. From my experience, if you've got a messy piston stop, you'll get a failing piston...

Be sure the piston head is made of softish rubber, and well-secured to the piston. Have you checked that the tee is fairly well-greased and the piston slides well? Can you hear it thumping as it hits the stop at least? Also be sure that the piston doesn't have the chance to slide it's back out of a ...

I've already got the capacity to reach 200 psi. I've approximated measurements above the gauge on my bike pump. I'm looking for 400+ gpsi.

The self-removing barrel was actually a problem I ran into with a very ghetto design, never thought of that as a safety feature...

Hmm, i'll draw it out and think about it, definitely something to consider.

Yah, I understand the concept. You'd need two pressurized air fill locations then though, wouldn't you?

You da man, JSR. That's exactly what I wanted to know. I'll certainly look into motorizing a shock pump, mostly because of the rated pressure tolerance on those things, I bet Ive got an old lawn mower engine somewhere that nobody would miss... So that stirrup pump just screws directly onto the gun i...