NOTE:regardless of what it looks like, the ratios are based on 8th grade math, if you want my formulas, they are (c1Rsqr*pi*c1l)+(c2Rsqr*pi*c2l):(bRsqr*pi*bl) where b is barrel, and c1 is the forward portion of chamber, c2 is the larger aft portion of chamber, as you can see by the math the ratios are based on cubic inches... Rsqr is radius squared.
DIMENSIONS: B24"Lx2"W C6"Lx3"W+12"Lx4"W C:B 1.38:1
Made with pressure rated Water supply ABS rigid core, rated to over 180psi, cost a good little bit, and nearly ruined tungsten carbide dremel bits(there is no black paint on it) dwv nazis back off
EDIT: I now have several barrels that can be swapped out, a longer 2"(I have a 10' piece im gonna cut either 6'/4' or 3'/7'), the original, and a 1.5"x2'
In this new design improvements include: larger chamber; all wiring hidden (i used a dremel to cut a grove in one of the coupling edges and sealed the wire in); a 1 inch piece of 1.5 inch pipe attached at 4 points in the aft end of the barrel to aid in barrel stuffing; new grip design; forward grip uses finger adjustable tabs to allow for side handle reconfigurations; all screws/penetrations are in couplings to give better structural integrity; a piezo-electric trigger built into the handle which is actually small enough to hold. ohh and the report is way louder due to the the new 1.38:1 C:B ratio, no reduced accuracy either
NEW AMMO! 2" fish bobbers with the trim shaved (dremel) and filled with anything sealed off with electrical tape. I used tempura paint, sand, or lead weights. there is also some cool stuff you can do with them, but thanks to a very helpful person, ive since removed that information
and the bobbers do not split until impact, filling them with paint makes basketball size or larger marks on anything it hits, like a jumbo paint ball, i do however completely wrap them in electrical tape, two layers leaves less than 1/64" of space all around so the tight fit gives a perfect shot, also i have a ramming rod with a foam ball on the end, i cover it with vasaline, and like gay porn it relieves all friction allowing for just enough back pressure as well as extraordinary side seal, leaving a tape streamer removes the aerial beach ball effect by creating a little drag which allows long distance shots, ive never hit a target larger than a basketball from more than 130' which is an easy hit as i achieve a good high velocity.EDIT: beginning to add components for measured propane, starting with the fan. I spent about 25$US at radio shack, on the fan, light up switch, and 12v(8AA) battery pack. I also added a male threaded piece to the old barrel, with just enough clearance to still attach the forward handle, i have also made a new barrel which is 1 1/2"x2' barrel (I will make a longer one, as this makes my C:B almost 5:1) and of course i attached a coupling to the original barrel.
assembly: the battery pack fits neatly away inside the front handle, and the switch is cleanly installed in an easy to flick position in the "trigger" spot of the forward handle. the batteries are easily removed via a 9v connector. the fan will sit directly behind the spark gap, and the wiring has eyelets on both the fan and switch ends, which allows me to attach them with a bolt threaded through the chambers aft coupling... this also allows easy removal. I thought i was just buying a regular fan, but it has LEDs(see pic) which I think will light up the smoke as i clears the chamber... just a nice perk
the propane metering system is being built now!
.Sweet amo too nothing like a little homeade pyro technics. 
