That is very impressive.
This can't be called spudgun.
Did you try shooting things at greater distances?

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Here is a tutorial on haw to make your own camera flash circuit:
http://www.kartoffelkanone.org/#zuender
(this is what i call "make your own...")
It is german but the diagram is very good.
I used this for the remote ignition on my Hybrid launcher. i combined it with a 6v ignition coil and it ...

A golf ball is aerodynamically optimized. The pits (grooves in the surface) reduce the resistance in flight.
A ball with pits can travel up to 3 times the distance of a ball without them.
I don't think that the tail can affect this in a positive way.

If you got all the wires connected to the right points in your circuit (whatever it may look like) you can try to check or just redo the soldered connections.

Keep in mind that its slightly illegal to own/use spudguns in Germany. So you better don't get caught with it.

This cannon?
You probably spent many hours and some money building it and it must be a pain in the ass to give it away but i seriously doubt that you will find a person willing to pay 750$ for it on this planet.

How do you know that ddt happens in a chamber. Explosion of the chamber may be a hint that it could have happened, but maybe it was for a completely different reason.
If a chamber is strong enough to handle the pressure spike there won't be a way to find out either the propane burnt fast or ...

I've found a cheap way to measure the projectile velocity.
I used:
2 switches
10m cable
stop watch

Looking at the old stopwatch, it has a resolution of 0.01seconds i had the idea for this.
I soldered two wires to the start stop button and connected the two switches in parallel.
One switch is ...

Maybe another mechanism is easier to make.
Found some rocket with a simple folding fin construction.
http://www.stormbirds.net/tech_r4m_rocket.htm
and
http://www.vietnamgear.com/kit.aspx?kit=501
Maybe it's time for a new prototype...

I did exactly what he described by accident.
My hybrid launcher was prepared to fire. I dropped in a piece of wood i wanted to shoot, it penetrated the burst disc and swoosh it was gone. This happened with a low pressure like 2bar (30psi) but i was luck to be not in the line of the projectile. I'm ...

I just made 3 more test shots (pneumatic) and it works quite well. Made a video but you can't see anything at all, crappy camera.
This prototype is not very damage resistant. I shot it with a pressure of 120psi. It hit the target with the brass cap first but the fins got bent an i had to fix it. I ...

Just an idea, correct me if i'm wrong.
If the combustion starts in the back of the chamber, the volume of the gas in this area increases. This means that it will push the still unburned part in the front of the chamber down the barrel, together with the projectile.
If the flame travels that fast ...

I wonder where the inspiration came from Wink

Almost right. I saw a picture with some different mortar grenades and one of them had these.
I admit that i had inspiration before making it.

Here are very quick responders. (9minutes)

just put together a thing i had in my mind for a week. Ammo with unfolding wings like a rocket. I guess this will make it rotate and remain straight in flight

In front of and behind the wings there is a ring, which fits exactly into the barrel and seals it. between the rings, the wings with tensed ...