Need help with design.

[KS-collector]

im thinking of a section at the back of the barrel, on a hinge with simple latch that I can drop the shell in and close.

that sounds like it could work, I would make the cartridges out of the same pipe you are using for the barrel, and if you find a sleeve which matches the OD of this pìpe losses should be minimal.

Thats a great idea. Thanks!

[jackssmirkingrevenge]

here's how I picture it.

[KS-collector]

Yeah, I was working on some ideas at my parents house, and thats one of the ones I came up with. I think if I wedge the football it the end of the chamber it should creat an air tight seal and hold the slight pressure from the propane. That way the projectile will be part of the shell just like a real artillery gun. Load the shell, fire, eject, reload. That way I wont need the door. That was on my original idea before I discovered your brillient cartridge idea. The football will have to fit loosely in the barrel cuz the surface of it will have lots more friction than a potato or tennis ball would. So id like to find a ball that has about 1 mm gap between it and the barrel.