Update on the current project and a little sneak peek: still lots to do (polishing valve seat, rebuilding piston to track more cocentric, some funny stuff with the barrel, a way to aim more better), but I managed to put a hole in my box spring with some supposedly "low power" testing and a plastic 1...

Since we're talking about rifling, have you seen how people are using "electrochemical machining" to rifle barrels from steel tubing? A very interesting way of doing it for those who are more at ease with 3D printing although I suspect it would be a challenge for rifle length barrels. mark.s has a ...