I don't plan on turning heads on this forum, I just want to make a functional possibly hand held hybrid capable of shooting a golf ball or ball bearing with some umph behind it. On this thread I will keep yins updated on how the build is going and ask for your input.
So far this is what I have. The plan is to use that 2"x8" pipe as the main part of the combustion chamber. A reducer and 1.5" nipple will lead into the 1.5" union. I accidently picked up a black iron union, going to have to exchange that (don't want to deal with the rust). I may or may not order a 1.5" cam lock to replace the union. On the other end is a 2" end cap. Instead of having 4 reducers and bushings to get it down to 1/4", the plan is to drill a hole in the center of the end cap and tap that for a 1/4" nipple. That will lead into a ball valve and then a pressure gauge to a T with ball valves going both ways with an coupling for air intake and a barb that will go to the propane tank. Ignition will consist of a spark plug in the center of the 2"x8" pipe hooked up to the stun gun. I probably will not go any higher than 5x mix unless I devise a permanent remote ignition.

Do yins think this setup will be adequate to launch a golf ball or should I go with a smaller union or cam lock. Also on that note, what do you guys think about cam locks vs union? I've been using a 2" cam lock on my combustion with a low pressure burst disk with great results.