I agree, there appears to be too much piston clearance. That thing should be so tight you need to really shove it in there. Also, I think you might be jamming due to the weight of the iron pipe cap in front. As the piston disengages, it will force the front end down and the back up making it jam ...

If you want a sabot that's molded to your projectile (think of the AB foam sabot that the MythBusters are so fond of using), a coating of non-stick cooking spray (or other oil) should allow you to place the projectile inside a spare piece of pipe the same diameter as your barrel and "cast" a Great ...

Umm...actually we first shattered the endcap entirely, then sheared off the end of the wye (and the attached pipe, and fill system, and solenoids). While (weaker) DVW components did play a role in this, we're mainly blaming it on a really heavy piston (~2 lbs.).

For details (and pics):
http ...

Launcher type: Piston-Valved Pneumatic, The Guillotine (10th post on page)

Temperature: About 57°F

Pressure used: 1st incident, 70 PSI
2nd incident, 50 PSI

Construction materials: Mostly NSF-dvw PVC fittings, SCH 40 NSF-dvw cleanout cap with pilot/fill system port in center (~1 in dia hole), all ...

Since the original question was regarding combustion launchers, the loudest setup would be a burst disc in a union. Multiple burst discs would not make the cannon louder, the bang is caused by the release of pressure from the chamber to the atmosphere. Since this cannon seems to be based more on ...

If you use a ball of paper towel slightly larger than the barrel as "wadding", you can fire just about anything, eg: rocks, whole cranberries(nice shotgun effect), small plastic bag full of water, etc.

What is the material for and dimensions of the barrel? (I am assuming you mean metal, but plastic can also be welded)

Also, it seems that brazing would be a more appropriate method of attaching anything to a ball valve, as they usually have a brass housing. Actually, it may be better to avoid ...

1.) PVC is usable for spudguns if it has a pressure rating somewhere on it (probably printed on the side of the pipe) however, it will fly apart if not properly primed and glued. I'm not sure where to suggest looking for glue and primer, aside from hardware stores and the pipe suppliers. It seems ...

The main issue with dual piston valves is the added complexity of building and simultaneously firing two valves. As for muzzle velocity increases, as long as your valve building is up to par, a single 3 inch ported valve will have a higher flow coefficient (and thus produce higher muzzle velocities ...