Need some advice, shotgun kinda.

[Schuyler]

I am wanting to make a single shot, shotgun style function for the spud gun I am planning. It will have detachable barrels, likely including 2" and 2.5" barrels, along with a 3" expansion chamber. It will use propane for fuel. I would like to make a barrel/attachment for this, so I can shoot somewhat of a airsoft scatter shot out of it. I have looked into burst disks, but it seems like these only work with pneumatic style weapons. Any info/ideas/help would be greatly appreciated, as I am extremely new to this type of activity. Thanks!

[FishBoy]

I would just use one of the barrels you're already making and then some TP as wadding, it will work very well.

[Schuyler]

Alrighty, thanks!

[CasinoVanart]

Burst discs can be used to quite good effect in combustion spudguns, the chamber pressure has a chance to rise before the projectile starts moving, hence the projectile (with a properly "calibrated" burts disc) will be subject to greater force upon initial acceleration.

http://www.spudfiles.com/forums/search.html , is a great tool to find long lost threads on different subject matter including burst discs.

Have a look around the combustion showcase too, you should be able to get a lot of good ideas just from looking at other peeps cannons.

Next best step is to either physically draw the intended design and let us rip it to pieces (j/k), i mean help work through it with you

Welcome to Spudfiles

[Schuyler]

I truly do not have a set design yet. I only know what aspects I want the cannon to have. These include:
Propane injection system
Car ignition coil
Detachable barrels
Safe

[CasinoVanart]

Why do you plan on using a car ignition coil, it is probably a bit overkill for what you plan on doing IMHO. I would recommend using a BBQ piezo or a stungun circuit (probly also overkill). A bbq piezo will cost you around 10$ and can be used with multiple spark gaps if you so desire.

[covey12]

take aluminum foil, place bbs in it, and shap it in a ball, drop in our barrel and fire

l l
l l
l l like that with the aluminum foil and fill it with bbs, it will
l l apart and send the bbs every where
l l
l l
l l
l l
l l
llllllllllllll

[Schuyler]

i used bbq last time with same chamber, and had to click it so many times to get a good enough spark

[CasinoVanart]

It was either your spark gap (should be around 10mm for a single gap), your fuel mix (i take it it was a "spray and pray"), or you just had a dud piezo, you get them sometimes.