SpudFiles

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras nec placerat erat. Vivamus dapibus egestas nunc, at eleifend neque. Suspendisse potenti. Sed dictum lacus eu nisl pretium vehicula. Ut faucibus hendrerit nisi. Integer ultricies orci eu ultrices malesuada. Fusce id mauris risus. Suspendisse finibus ligula et nisl rutrum efficitur. Vestibulum posuere erat pellentesque ornare venenatis. Integer commodo fermentum tortor in pharetra. Proin scelerisque consectetur posuere. Vestibulum molestie augue ac nibh feugiat scelerisque. Sed aliquet a nunc in mattis.

The pressure of propane is highly temperature dependent - but normally is far south of 300 PSI. (I think the emergency release valves on those tanks generally activate at around that pressure)
http://www.engineeringtoolbox.com/propa ... _1020.html

They do have a point, though - propane is more expensive per shot.
(I'm calculating .2$ per 2 liter chamber at 100 PSI)

That said, it looks like you want a fair degree of velocity consistency... so you want something less manual than a ball valve.

I advise you to download and play around with the GGDT... with the acknowledgment that it doesn't have propane as a gas option.
(though I think joanna posted the data needed to enter it as a custom gas on spudtech)

MrCrowley wrote:I doubt you could get 250fps with a 20" barrel easily.

well, unless you have the valve and chamber to support it.

If you do, you can achieve high velocities pretty easily.


does anyone know what airsoft thingy he was talking about?

Don't take these guys flaming you to hart. Your just new to spudding? Pay more attenchion to Mr Crowley's post, for your sizes. Go to the spud wiki and read up on pneumatic cannons and solvent welding before you start building, the link is up top. We do like pictures around here and video's are even better, of your cannon's, just wanted to point that out. Welcome to spudfiles.

I don't know what he would use a GBB for in his design (BTW GBB means Gas Blow-Back, a gas powered blowback airsoft gun).