Since the prices for the parts over here is ridiculous, this small gun cost me about AU$120. It's made out of PN 18 (means it can hold 18 bar) parts all the way, couplers and pipe, so i don't think it'll be blowing up any time soon like Trinity did (see combustions).
the chamber is It's a modified sprinkler valve for the actuation, I done a S#!t job on it though because it was the first one I ever made, but it does work fine, I just have to pump up the sprinkler valve before I pump up the chamber.

I'd love to hear any feed back for it, the barrel is short, but thats because my mate snapped it, and i had to cut it



P.S I have a video of my combustions and some bombs I made last year on ebaumsworld.com under the URL http://emuse.ebaumsworld.com/watch/13374 Please check it out and rate it for front page, much appreciated.