SpudFiles

This is the Negotiator 3. It's a 3/4" porting 1.25" piston valve gun, actuated by a blowgun. The barrel is 3/4" EMT. The 1.25" Tee allows for using 3/4" sch40 coupler and endcap for the piston, and the gap between those two creates an o-ring grove.
sorry for the fuzzy pic.

How long is the barrel? Cool launcher by the way.

Thanks! It's a five foot stick, that's all I could find. It's pretty dang long; the whole gun is 6 feet or so. It's also pretty heavy to be holding with the center of gravity that far out.

Yeah, maybe you could move the handle and everything forward to make it more comfortable to hold. Then add a grip in the front with linkage linking a trigger up there with the valve in the back to keep the pilot volume down.

thats a cool looking gun you got there.

its basicly an elarged version of my piston gun, i like it.

@pyro: I'm not sure I understand you. My left hand is holding the bracing block that goes between the chamber and barrel, I guess that's what you were calling the handle. The trigger/handle that I have in my right hand is a blowgun. The PVC hanging off the barrel in front of my left hand was supposed to be part of a sight; that didn't work too well.

The main reason I can't move everything forward is that my stock is so long. I wanted it that way, though: it keeps my face away from the breach, which sometimes pops open during a shot; it also protects the schrader valve and hose connections when I set the gun down on the butt.

Oh yeah, the breach. It has an o-ring sealed PVC assembly (also involving some aluminum tube from a lawn chair leg) that slides on the barrel, with a twist-lock set up to connect to the mouth of the gun. Since the barrel is held on the bracing block only by cable ties, when I open the breach the barrel flips up like an old-school shotgun barrel does (break breach, I guess you'd call it).

Hmm. I should get a better picture of the thing somehow. I don't have a digicam, and my cellphone camera really sucks. and I'm too lazy to shoot a roll of film and get it on a CD just for that.

Looks like a good cannon. What do you like using to shoot?

Well done

I mostly shoot potatoes, paintballs, and marbles. The paintballs and marbles need extensive wadding. I've tried a few nail darts, with varied results. The ones I made with paper cones disintegrated. I need to make some plastic ones eventually.

I also built a 3/4" CPVC barrel for paintballs, but it still didn't help my accuracy with them. For some reason, the balls go about 200 ft and then suddenly corkscrew and fly off in random directions. They may deviate from their line of flight by 20 or 30 degrees! I have no idea why they do that. Of course, they don't fly terribly straight up to that point, but it's the consistency of that phenomenon that has me puzzled. It doesn't happen if I shoot at relatively low pressure (50psi or so), but above that it always happens. Ideas, anyone?

You could also mold some wax slugs with lead centers. They fit perfectly, have nice weight and are relatively cheap/fast to build.

The paintballs probably curve because of 3 main factors (there are others)
1. They are very light, so any wind will blow them off course
2. They arent even weight, the paint is varied in thickness/density
3. They spin out the barrel

All these factors cause the horrible curve you getting.