Air cannon project: Upgrades!

It's a rainy Thursday afternoon, and I have nothing better to do other than work on my cannon a little. I decided that the simple design I built the other day was far too long to be practical for transport and trying to aim it was awful. So, I made two changes that has fixed that and should give me a little more power too.

First, I changed the chamber to an over-under layout, so that the length of the chamber is essentially halved. Using two 90 degree bends gives me a flat area to put my shoulder to achieve better aim, and the added volume of the bends slightly increases the overall chamber volume. not only that, but I can now stand the cannon on it's end for storage without risking damage to the fill valve, which is now under the main valve instead of at the end of the cannon.

Tin foil burst panel to be seated between the
back of the barrel and the o-ring on the other half

Secondly I wanted to be able to remove the barrel for storage and breech loading capabilities. I was originally going to cut the barrel and add in a simple male/female threaded fitting, but I was lucky enough to find a union coupling of the correct size at Bunnings, which means I can also add in a tin foil burst disc, sandwiched in the coupling. The burst disc won't break until a certain amount of pressure has built up behind it, allowing more time for the ball valve to be opened which will increase flow and increase initial acceleration of the projectile. Having the barrel removable also means I could build different barrels for it, possibly a Nerf dart barrel? A vortex mortar? Or even a paintball bazooka barrel? Oh the possibilities... Testing with projectiles might happen on the weekend, if the weather is good.