Yeeeeaah. I'm happy to post any dimensions. I'll have to admit I'm behind in the CAD department. I keep looking for something that I'm willing to invest the time into the interface. I need an old copy of autocad 12
I did a bunch of sketches on sketchbook, but made adjustments for the tooling I had available. The spool was going to be 3/8" nominal, but I bunged up my 3/8" bit years ago and it makes an oversized hole, so it is all 23/64". I'll be making a drawing though. I've already forgotten where some of the dimensions came out. Fortunately, it is a pretty tolerant design.
One reason it is laid out this way is so that you can change out the spool design. You can do an unbalanced spool by reducing the breech plug ID. I would like to get some CFD software and model the front cone and test out different shapes. With a threaded sleeve, I can go back and reduce the whole spool diameter. I checked the stresses around 300 psi and had a worst safety factor estimate of 3 (accounting for my poor machining and a silly bad fit), so it has some tinker room. The opening force can be manipulated with the internal spring and the balance of the [spool]. I wouldn't do a forward moving spool without checking the stresses because you would want to make it thinner relative to the front seal. Once you get it well above the seal friction, your velocity consistency should be only in your starting pressure and paint to bore match.
Once it's nice and consistent, this would be a lot of fun as a dueling pistol with first strike rounds. I've been studying WALZ's stocks and would like to dress up a pair. If two people brought separate pistols, I would say you trade pistols for at least the first duel, even if the FS rounds put you at good distance.