I just added another photo... this is my project finished (however i have to replace the lighter starter with something better like a circuit from camera flash or something similar...)

I was thinking about an electric valve (like that used in gardens etc)... when it's opened can it holds more than 10/15 bar? My idea is to open the valve and after ignite the gas in the barrel (but this could require a longer barrel, i suppose)
What do you think about it? (I had this idea reading ...

Oh, sorry... i've just read the thread "valve setup in hybrid" and now i know that sprinkler valve holds 150 psi max... so the only way is the burst disk
Sorry for the ignorance
Anyway other solutions are accepted ^^ (obviously they should be compatible with my project!)
See ya!

Uhm... i don't know... but i bother to add a burst disk anytime i gotta shot a potato! -.-''
Isn't there another solution to the burst disk?

If i can find a cheap sprinkler valve, i'll use it where fits the barrel, otherwise, i'll put a burst disk at the same place (after the curve, before the barrel).
I bought the unions, so now there's only the hole for the spark plug to be made... and this afternoon should be complete (except for ...

Mmhh thank you boiling for reassuring me ^^
However, i've just downloaded the image from the camera... here it is ^^
I made some modification to this project, so something isn't where you see it now, i'll update it when i have new joints.
The barrel is jointed cause i can detach and screw it to fit ...

For everyone is making a full metal hybrid: 2" iron pipe with 3mm thickness working pressure is generally 50 bar, i've just found it on a datasheet.
So i could try to use a 4x-5x mixture, like prometer hx says. But i'm not sure a 5x mixture (with ddt) will cause only 50 bar... however, my cannon isn ...

does anyone know where to get starter fluid with propane or a similar propelant.
I think you could use a pressure proof tank (hardware store) and a normal gas tank (from a gas heater or from a barbecue for ex.); then just use some copper pipes, a compressed air regulator and a manometer to connect ...

Oh, thank everyone for the answers! :D
So... the pipe diameter is 2"; its thickness is 3mm... so the external is 2.12".
About the type... i really don't know, i bought it in an hardware store and it the same kind of iron used for my house's pipes... however, the blow test is beyond my possibilities ...

OK, either use the spudwiki, and if its not there google it.

We are not google.
Yes, i tried and i found nothing. And on the pipes there's nothing written...
However, the spudwiki lacks about iron and any metal made guns... so...
About google, i found on wikipedia the general resistance of iron ...

I am making full metal hybrid with iron pipes. I did made some combustion ones time ago... and now i think it's time for the hybrid! :P
However, i'm asking how much pressure can carry a metal chamber 2" x 10" (3mm thickness or more where there're joints)... anybody know it?
I'll post photos as fast ...