An syring-based laucher

[wafen]

Recently I've found that a syring [or a injector] could fit well with the 6*4mm[.25*.15in]plastic tube and it could use as a mini cannon.It is easy to bulit and could be use for a lot of times.The one I'm using now has operated for about 1,000 times ,and it's still operationable.The metal barrel was not suggested,for it would be easy do damage the syring so that it will leak from the place where it was connected to the barrel.
The shell I used was steel ball.The ball you found may not fit well to the barrel,but you can try with this way:put it in a baker,or something you could found like a plastic bottle,then add with acid，like hydrochloric acid,sulfuric acid，and wait for sometime,maybe 20minutes or more,until it fits the barrel well.Remember to wear protections while dealing with acids!
A proper thickness of the plastic thin film would be important,and you can find it in many ways,like plastic bags,etc.The more thickness you choose,the more power you get to fire.But on the other hand,it will be harder for you to fire.The thing i choosed was from napkin's pack,for it would brust at about 0.65Mpa,or about 95 psi.
The barrel length is another important factor.As far as I tried,the 5ml fits for 10cm[4in],and the 10 or 20 ml fits best with 20cm[8in]barrel.I've got the barrel built up by used gel ink refill.The length in the picture was unnecessary,it was for a control test.
The muzzie speed would up to 90m/s,or 295 FPS,and for the ball it means 1 joule.As it is smaller ,it could be as powerful as the BB at 130m/s[430fps],and it could easily break the window or someother glass.However,this speed was operated with 20ml syring and I doubled the thickness of the plastic brust film,which made it more difficult to use.As for the 10ml ,normor version could be as low as 50m/s,or 165fps,which was appr.30% of the maxium one.
Because now I live in PRC,the syring I used might have have some difference with yours.For the same reason ,I mainly use metric units,there maybe some mistakes during I transport it into British units.
Sorry for my not so good English describings.If you have some problem or found mistakes,just left a comment.

[jackssmirkingrevenge]

Welcome to the forum!

Quite a witty implementation of a burst disk that removes the need to compress the air quickly.

The "needle shooter" uses the same concept but relies on friction to allow for the pressure to build up.

[Cthulhu]

Welcome,
I like the use of the magnet to hold the "shell" in place, that's a pretty neat design!

[Anatine Duo]

Nice use of available materials. Thanks for sharing your data.

[wafen]

Thank for your guys supporting me.Here are some more photos,hope them can help you if you wang to try it