same manner as the InlineVortex, I decided to make a small piston
pneumatic as cleanly as possible. By using 2" SCH80 pipe as the
chamber, I could use 1.5" fittings to eliminate the need for 2"
couplings at the chamber ends. This results in a more graceful
appearance, adding aesthetic value. I'm surprised that no one has
previously done this (to my knowledge). Of course, as a mini piston gun
it is internally very similar to others.
The diagram below shows the internals of the minipiston pneumatic. The
air input is your typical schrader valve, and to help seal I added a
light spring I had lying around (it originally was inside a Watermaster
1" sprinkler valve). The blowgun pilot works well enough, even though
adding a QEV or even just a ball valve may work better. However, since
my priority with this launcher was aesthetic considerations before
power increases, I'll stick with the blowgun. The piston is made from
1/4"-20 threaded rod, 1/4"-20 bolts, 1.5" fender washers, and a 1"
neoprene fender washer as the sealing face.
To remove all the markings from the pipe I took two courses of action:
scrub with PVC cleaner and polish with lacquer thinner. The former,
when applied with a shop towel to only the marked areas, removed the
ink very quickly. The latter is best for making the pipe very shiny,
and although it will remove the markings to some degree it is much less
efficient than the cleaner. Use the cleaner to remove 90% of the
markings, and use lacquer thinner to get the rest and generally shine
up the pipe to a glossy finish.
The favored ammo for this launcher is .50 caliber lead balls or .50
caliber BMG bullets (450 grain!)
that I bought for a nickle a piece at a gun show last year. I still
have about 20 of them, and with a small paper towel piece as wadding
they perform very well. Without rifling they tumble in flight, of
course; however, they're still very large and dense, and do wonders
against a 1/2" plywood target.