I've been working on an update to my pump-action SNAP, and have something of a mk2 version ready:
Instead of using fragile hard-to-find 1-1/4" thinwall PVC for the grip section, this verion uses three 1-1/2" PVC couplers. Gorilla tape holds them together very firmly, so much so that I completely skipped my plan to epoxy them together. The center ridges inside the coupler need to be sanded down just a bit with the dremel before they will slide freely, but it is not very much work.
Instead of using cross-bar for priming, I simply use a 10-24 screw. The one pictured is too long, so I had to prop it up using nuts - a 5/8" screw should be just about the correct length. This is a hell of a lot easier to make than the cross-bar design, since you only need to cut one slot, and that slot doesn't need to be off-center.
The most prominent feature is that the body extends all the way to the end of the barrel. The barrel is supported on one end by the hopper, and at the tip by a bunch of couplers, so that it does not wobble independently from the blaster.
The internals are the same as my other SNAP, so you can follow that thread if you want to build one. Also dry-fireable, because why not?