Monte, my spudgun is a 2inch pipe about 3 feet long. The chamber is a 4inch pipe about 6 inches long. I've got a 1inch SS ballvalve on the end for injecting in the propellant. I drilled a 1/4 inch hole in the end plate of the chamber for a flash hole. Put a piece of tape over the hole, inject your propellant, close the valve, and wave a lit oxy-acetylene torch over the flash hole. The first time I ever shot it, we loaded up a spud, put a 12 second charge of neutral gas in it, and cut er loose. I think that spud is still orbiting. Out back of the shop where I work, there is a row of trees about 150 yards away. That spud cleared those trees like nothing. We howled our a$$es off!! Try neutral gas. Get a torch going, then snuff it out. fill the gun with the gas coming out of your torch. It's real explosive so don't get carried away!! Enjoy