We upgraded our irrigation system some time ago, going from a above-ground pipe and valve system with water towers (simply giant sprinklers set up on our field), to an underground, sprinkler-heads and pipes system. In the process of making these improvements, I had three large ball valves (not that large, 1" ers to be exact) that I cut out from the old system when I discarded it, choosing to save the valves for "projects", should the time ever allow it.
Well, just a couple of weeks ago, my now 12-year old son, who has become a COD4; Modern Warfare fan, asks me, "Hey Dad, can we make a Nerf RPG?"
My answer; "Son, you have a Titan, and a Buzz Bee Blast Bazooka.... there's your RPG."
He said, "C'mon, Dad, those don't look like an RPG!"
So I decided to finally put those valves to good use. Nothing complicated, really.

Simply an inline ball-valve homemade, with a pathetic attempt to make it look and feel like an RPG-7.
The front handle actually has a 1/2" SCH40 PVC barrel running through it, so there's no air loss at the hand grip. The threaded sleeve ball valves mean easy maintenance, and running the collars a BIT loose makes the valve snap open easily, plus the larger red lever allows enough leverage to not make it a chore to open. The Franklin ball pump is epoxied into 1 1/4" SCH20 PVC (thinwall), and that is PVC glued to the coupling and the air storage. Ammo is stomp rockets, Max Shot bombs, and occasionally, darts. The rockets go about 60 feet flat shot on three pumps (t could go more, but I don't want to push it with my son as far as something failing on the design and blowing up while he plays with it).
Finally found a good use for that flip-up Recon sight too.

Not wanting my kiddo to have all the fun, I decided to make something for me, too. Kind of a cross between a Ithaca MAG-10 (one of my favorite longarms), and an M79 grenade launcher. Something to just fool around with, not to shoot anyone unless they were deciding to use some goofy cardboard armor/ tank/ fort.
Here's "Harvey Wallbanger".

Yeah, it's short, stubby, and ugly. Just how I like it.
Filled with a foot pump, I" barrel, haven't decided exactly what to shoot out of it. I made some projectiles out of 1/2" SCH40 PVC and electrical tape. Those are a bit scary. I'm trying to experiment with a 1 1/4" SCH20 (thinwall) PVC barrel, and a load of SIX 3/4" FBR darts (each dart larger than a suction cup mega) similar to the ammunition from my old SM5000 Roadblocker project a long time ago.

Paint job is next. It'll be kind of "business" looking, not a toy, but not something that will get my neighbors worried.
Sure wish I had a video camera for the trial runs. They look promising. 25 feet + 20 psi = holes in cardboard boxes (as in RIGHT THROUGH them).
What fun for a couple bucks of PVC pipes and old valves. I have one more valve, and now my son wants a howitzer. I'll probably give him my 2" solenoid valve spud cannon after building a frame for it.
-Piney-