Reliability stacks, the more parts, the more often the machine stops. Theoretically, a spool valve like you built with one moving part should be very reliable. However, you probably need to look into how the seals on DCV's are done, O rings rarely like to move past porting, having the o-rings seal i...

I used to be the same way. I still rarely use it these days, but it's the unfortunate truth.

Very nice project! Since we're talking about rifling, have you seen how people are using "electrochemical machining" to rifle barrels from steel tubing?

Pretty good for a nailgun! :p I have a few recommendations for the next one, though. That chamber is pretty massive for a 1/2" barrel. If you were to use a smaller pipe size for the chamber (say 40-50mm) you could probably find some better pipe which is either rated for pressure or will hold up bett...