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I was thinking of making bullet catridges except the propellant would be a high-pressured gas and the primer would be a burst disk. The hammer would pierce the burst disk and there she blows! But just a few questions.

Which gas should I use and what PSI should I use for good and fast thrust?
What should the bullet be made out of that is cheap and can make a quantity of them?
Is there any problems in this design?

you want a cartridge, but you want a burst disk, i fail to imagine how that will work, btw they have air powered cartrigdes already, they are tiny piston valves

i had an idea posted like this except the bullets had propane in them and then they would have been zapped.

I guess I don't really see the point in making "bullet cartridges" for potato cannons.

And I really don't see the point in mixing a burst disc with a "bullet cartridge". If you're going to build cartridges make them with propane or some other type of flammable gas.

Just came up with an idea, this would be fired off like a normal cartridge, a hammer hits the pin which pops the burst disk between the ammo and the air. To make the union, you could have 2 sections that would be held together with 2-4 small screws, you could also tape the 2 halves together.

A
how do you seal that thin hole?

B
what stops the pin from shooting out?

two questions easily answered but not easily done

Well here's those easy answers:

A: Rubber Silicone, just pour it on there and it should act as an O-Ring.

B: The force on the nail would be minimal, so just a ring of tape or a piece of solder should hold it in.

Should'nt be too hard, ironically I was drawing up this design right before I saw this thread.

Easily done: glue it in place with a weakish, brittle glue, and hit it hard enough to break the epoxy. (easily done if the nail is polished)

And easily answered too.

Of course, such burst disk actuation meathods suck. I'd look into a 1.5" combustion cartrige. The tight fit in 2" sch 80 provided a handy way to mate the barrel to the cartrige. Seal it with a well-fitting ammo.
If one where to use sdr 21 for the cartriges, you could use a riffled barrel. The taters would dig into the grooves... although we really want a pipe with a diameter of 1.65"... perhaps one could use a 1.25" coupler to hold the potato? (ID ~1.66")

That would also work, I'm gonna try to make a version of the http://www.boltsniper.com guns that will fire these.

Simple Idea, find ammo that has a lot of friction, then add pressure to the cartridge where theres not enough to push it out, then have the pin push the ammo and then the air should do the rest.

carlbelcher wrote:I guess I don't really see the point in making "bullet cartridges" for potato cannons.

And I really don't see the point in mixing a burst disc with a "bullet cartridge". If you're going to build cartridges make them with propane or some other type of flammable gas.

1. Full-auto and semi-auto is possible
2. Not having to worry about carrying around a compressor or pump
3. It's cool

I agree, the cool factor is all you really need. I need to build a standard pneumatic first.

I don't think that manufacturing enough of these to have "full-auto" or even "semi-auto" is going to be cost or not to mention time effective. If you want portability build a co2 setup! I'm not saying that it's not an interesting idea, I just don't think it's very feasible.

Lol. I used to be a nerfer and it took about an hour to make micro stefans (custom nerf darts).

So I'm guessing it'll take around 25 per hour for these. Still looking for a material for mass production though.

The idea of a cartridge has been discussed before: http://www.spudfiles.com/forums/viewtopic.php?t=1350&

The reasons I wouldn't use combustion-type cartridges:
1. It wouldn't be very safe to carry them around. The explosive mix could be set off by static electricity or a number of other sources.
2. They'd need to be pretty large, compared to the rest of the gun. Lightweight, yes, but they'd be a pain to transport.
3. A solid propellant cartridge is easier to manufacture, smaller, more powerful and safer. But that technology is beyond the scope of this forum.

All in all, we already have them CO2 12-grams. Sounds to me like they're the best option for now.

Well,you could have a 2x mix in the cartridge and a projectile sealing the one end like a normal round except you put a plastic cap for the ignition source.This will allow you to have a set up similar to a normal fire arm. There are some issues like how you would pressurize the cartridge and how you would make the cap pressure resistent.