SpudFiles

Hehe, the first thing I thought when i saw this cannon was "is that made of meccano?"

Crap, I'm turning into some form of tyrant

no, i would just call you a big meeny head.

It's a solenoid valve alright.

About the foam tip..
There are kinds of foam that are open structured, but also kinds that have a closed cel structure.
The latter will obviously not work.

There is a big chance that regardless of the type of foam, it will get blown to bits.
If you want to have a silencer, than build a proper one.
Like what you mentioned, but inside a container, usually a tube.

Using the absorbing kind of foam ofcourse...

@wngovr
what did you use for the trigger ?

POLAND,
I posted that link at the bottom of page 3.

Yippy kai aye mother plucker!
That's blurring the line between potato gun and big bore airgun! (...Oh for some way of making rifling! )
I love it!
It looks like you could, (if you feel like it's warranted of course,) move your foresight to the end of the barrel to give a slightly longer sighting radius.
Have you chronographed it at all?
Beautiful, simply beautiful.

well you need to fix the....... Just kidding this is absolutely perfect! any video of it in action?