I would use a spring to move the piston not a finger, there might be too much pressure. This is exactly a design from ant(but then different ).

http://www.spudfiles.com/forums/automat ... 13665.html Heres a link
Tom

There will be allot of force on the part thats connecting the hammer and the barrel. Maybe you should try to build a much more simple design, look in the BBMG showcase for some idea's. especially ant's ones
Tom

It's looks very very real, I like it allot. I first thought the led's where infrared lights so you can see in the dark .
Tom

If you going to make this gun, I would make the wheels out of the scroll knob of a mouse. I used them for a RC mous , they have allot of grip.
Tom

I would steal one . Just like said above you would be better of buying one.

I made a HV power supply with a flyback transformer once. What I did was not using the pins under the transformer, i wounded two coils on the ferrite on the transformer :!: . Here´s a link to..."The amazing site of sam barros" :D http://www.powerlabs.org/flybackdriver.htm I hope it helps Tom PS: Don...

I just went to the shop to buy 12mm OD copper pipe and 10 MM OD alu pipe. I tested is they would fit in eachotter but they didn't did you had that problem too?

Today I have tested IT . It works very well, better than I thought it would do. I don't know how far it shoots, but it's very loud(and thats is very important . Thanks for all the help
Tom
PS: I will post the pics in the launchers section soon.

IT doesn't look anymore with a short barrel i think

If your fuel doesn't want to ignite it is probaly that your sparkgap is covered by those plates, but it looks good.

They look like rockets to me

Is that sarcastic?
It's a bolt that prevents the projectile from rolling down in the chamber.

Thanks for the comments, I know my english is bad. But rather a good grammar then those stupid posts with alot of bad grammar. BTB I'm using pressure rated PVC pipe. I will dril a now hole for the projectile block to make the chamber bigger.
Tom

ARGH.....
ahem.
It's just like you said "75mm diameter and 1000mm long". My propane meter is finished, nut I need to go too school .

I had the some problem(probably), there is a maximal of one minimeter between the three electrodes. I think it will work with that little spark gap it also workout with mine gun that was to times bigger. So you do not really need a ignition coil, but you can always use one if the small spark gap doe...