Ok I have it going now with a very tight piston but now it won't hold over 40 psi, past that it just leaks out of the barrel.

Its been a while but I decided to finally make another cannon. But I have a problem the piston seals and pressure builds but when it comes time to fire all the pressure is released through the pilot valve which is a 20mm sprinkler valve. Is this because the piston is not tight enough and it will be ...

For the valve I used a modified direct acting 3/4" sprinkler valve, I took out the diaphragm and made it so the solenoid armature opens/closes the barrel like the diagram.
I'll get some pics up soon.

I made a prototype today and it works apart from some sealing issues.
ie. It leaks alot but the valve obviously works.
I'll hopefully get round to fixing it up in the next few days.

Ill have to start saving up then. Where do you think Ill be able to find a 6mm tee. Maybe Ill have to make one in my ghetto machine shop.

I was either going to shoot 6mm bb's or .22 air gun pellets.

Here is a new design that I came up with for a small calibre semi auto pistol. The tank would be filled with either liquid propane or high pressure air. The solenoid would open for a split second allowing only a tiny amount of gas to pass through and hopefully allow for multiple shots. Any ideas for...

Just got my 200 6mm necklace beads of eBay today, perfect fit in my barrel.

For my Aussie Plinker I used some 6mm aluminium tube from toy world and I bought some (expensive) steel bb's off eBay. I just bought 200 6mm glass beads of eBay yesterday and they were pretty cheap, like 10 bucks for 200.

The propane will only flow until it reaches around 120psi, depending on ambient temperature. So I just open the valve on the tank until the hissing sound stops. The expansion rate of liquid propane is 270:1 so at 15 degrees celcius so according to my (dodgy) maths I should be able to get around 2700...

The new Tippman is actually a combustion. I've shot this and my other bigger guns at a flame with propane and the fireball for the big guns was big this one wasn't really good.

The chamber is sleeved for looks and those chips are only on the outer piece of pipe.

15mm pipe works well, but when i want extreme power I go with 20mm PN12 PVC and paper towel wadding.

We'll have to find somewhere very secluded. Way out in the sticks we could even set up some tents and camp, it wouldn't be the most illegal thing taking place anyway.

Sounds like there is plenty of interest, this might actually work.