SpudFiles

This design is nothing new, although I have not seen a mini verion of it, it is a mini breech loading coaxial design. The cannon breech loads through the tee, and is made with galvanized steel pipe fittings and malleable iron fittings. The majority of it is 3/4" pipe, although the tee is 1 1/4" to allow the 1/4" tee to fit inside.
I will be making heavy use of epoxy (cross your fingers, I have not used it like this before) to attach the brakeline to the galv. pipe, unless of course there are some relatively inexpensive fittings to the the job. The diagram pretty much explains itself otherwise, but some basics are:
3/4" epoxy piston
1/4" brake-line barrel
Breech loading
Blowgun exhaust

Things I have yet to get:
1/4" threaded schrader
1/4" brakeline
Shock Pump
Probably some other not as important stuff too.

Questions and advice are welcome.

I guess that would work just as expected.
Cant wait to hear if it worked

Looks pretty good so far. Seems like it could take realy high pressure
If it was me though I would have a bigger barrel.

Thanks for the replies, hopefully it should work, my main worry though is leaks through my epoxy bonds, but I should be able to avoid those.

The barrel is not drawn to scale in the diagram and is not present in the picture. It will extend about 2 feet from the chamber, so hopefully that will be enough.

I have come across another problem, and was wondering if you guys have any advice. The inside of the 3/4" galvanized steel pipe is quite rough, and Counterstriker tried unsuccessfully to cast an epoxy piston in it and it got stuck in the pipe.

One possible solution to this problem would be to use 1" galv. pipe instead of 3/4" and then sleeve 3/4" pvc (sanded to fit) inside that pipe to house the piston. This would make sure there would be absolutely no flow restriction. I am tempted however, to use 1/2" pvc and to make sure that it does not encase the end of the barrel. This would be a little bit tricky though, because everything is threaded, so after I tighten it all the barrel could be too far forward, causing big time flow restriction. Here is a diagram:

Well it seems possible to me.
Just make sure you get things measured out well.

I'll be sure to tighten everything before I sleeve that 1/2" pipe. Anyone else have any advice? Some of the epoxying worries me.