SpudFiles

This is my newest cannon, which I named the "Excalibur". It is built around a 3/4" QEV. The chamber is about 30" of 2" aluminum pipe, and the barrel is 3 feet of 1.5" PVC. I have 2" cam-lever couplings for breech loading, though I need to create some kind of cartridge, otherwise it is very hard to load with no barrel detent.

I finished it today, and although it fires, it is not yet complete. I was in a hurry to complete it, and experienced several leaks and part failures, and had to make do with what I had on hand (hence the 2" tee on the end of the chamber, which I intended to use as a temporary coupling.) The pilot valve is a 3/4" ball valve, though I plan to replace it with a 3-way valve to make filling and reloading quicker.

Muzzle energy is fairly impressive, and I expect it will be even more powerful than what I experienced, since I only aired it up to about 40PSI today. I plan to go as high as 120 with the PVC barrel, and up to 300 if I get an Alum barrel. The only thing I shot today was a wadded up sock filled with candy (for a Halloween party).

Several major upgrades are in order including:
3-way pilot ball valve
Cartridges
Paint job for PVC parts.
Onboard CO2 system (eventually)

The PVC barrel can take 300 psi. There isn't one part on that gun which would make it dangerous at higher pressure.
Nice job overall. Your upgrades sound promising. I suggest you plug the other port of the tee, and put the QEV on top with the pilot facing the back. That will make it more ergonomic and better looking plus it would eliminate the dead volume in that little elbow which is also restricting flow to your barrel.

Thanks. If you look closely at the tee, you can see that it is already plugged. I will be replacing the tee with a normal 2" coupling soon, at the time a tee was the only thing I had on hand that would work.

What kind of paint sounds best: desert camo, or flat black?

I know it's plugged, I was just suggesting you plug the other port and change around the configuration on the valve to make it go directly into your barrel. As for the paint, I think a flat black barrel would go nicely with your chamber.

Good job but shame about the 3/4" flow restriction, if you want to give power a significant boost simply put a disk in the camlock after loading

Actually, my cartridge design includes a disk.

nice job, with higher pressure and disk that is going to be beast!