SpudFiles

Yeah Xbox, the larger sections of pipe automatically come with one end of the pipe flared, so u can get one flared barrel per 10 or 20 feet, depending how you purchase the pipe. My local store only offers 2.5" pipe in 20 foot sections.

As far as making a piston valve, I haven't had any luck at all so i just keep with the sprinkler valve since that is what works for me.

Thats fine, I haven't had any luck with piston valves yet either, but I've seen my neighbor make them so I know its possible. I'm planing on making 2 piston valve cannons soon(hopefully they work) One is probably going to be a tennis ball cannon that my neighbor and I will build together and the other is going to be just a gun w/ a 1/2 inch barrel, nothin' special, although I may make some cool loading mechanism for it. My new air tank should help w/ piston gun testing! Good luck with any future piston attempts.