It's got about 4.5' of 1.5" sch40 for the barrel, and 1.5' of 4" for the chamber. This ratio works really well: it's loud, but I get high velocity. And it's also as tall as I am (~6ft). Ignition is via BBQ ignitor and a homemade spark plug of threaded lamp rod, HV wire, and rubber tube.
I've got a propane meter for it, but I haven't mounted it yet. Problem is, the meter is longer than my chamber is! I had a chamber fan at one point, but since I only used one 9V battery it was slow and didn't do much good. Besides, I don't like having more expendables on the gun.
The blue rag on the barrel is the ghetto shoulder rest. I wanted to use some pipe insulation foam, but I could find any that big.
my friend modeling the Pwnager

another angle:

myself with a side view of the gun:
