There's not too much to say here. The gun stalk is a piece of PVC pipe. The brass rod is from a model shop and bent in a vice. I cut holes in the pipe that were slightly narrower than the rods and they just push fit tightly. The whole thing is primed and spray painted black.
The arm balls are Bocce balls from the game (a little like the French lawn game, Boule, I think). They're solid particle wood, so they can be drilled. But they come with a fine finish. Unfortunately they're only 3.5" in diameter which is slightly too small for the purist.
The plunger is just a sink plunger painted black and with the ribbing removed with a scalpel. I sanded it with an orbital sander to remove the evidence. The outer tube is electrical conduit.