True...it came from one of Mitchza89 posts/projects.

What is the gray box? Is there an advantage to using it?

What do you mean by a multi shot blowgun setup?

No...sorry. I have a 1/4" brakeline that is 18" long. Using 3/4" copper pipe as the chamber, is there a need to have the piston side of the barrel supported?

In a coaxial gun that is 12" or greater is there a need to have the barrel supported by something? Is there an optimal length to use? I am having a hard time visualizing it.

I want to make an airsoft rifle. I also want to use a coaxial design. I know the barrel needs to be a brake line, but does anyone have a suggestion on what to use as the outer chamber? Is there anything out there that someone has already used?

"Very little gap around the piston"

Do you mean the circumference around the piston or the distance between the end of the piston and the spring?

Does is matter how much distance the piston travels in order to seal the barb?

edit1:
How should the piston move through the chamber...with easy(would ...

I am using a 3/4" metal tee and a 3/4" nipple to house my piston. I can get the piston to seal the hose barb, but once I add the air tank to pressurize, it breaks the seal and air leaks into the barrel. I have several questions:

How much space should be between the barb, piston, and spring ...

If I were to walk into Lowes, Home Depot, etc, what would look for. Is the "T" a compression fitting or something else? And what are the other bits called? I understand it is his piston.

I captured this from spike33127's youtube "making a QEV" video. Does anyone know what the three parts are that I labeled with arrows and where can I get them?

Has anyone tried melting and molding PVC to make their vortex block? It has a rather low melting point and some noxious fumes(I believe). I have seen some people heat and flare the ends of PVC for rockets. Just a thought...

Switched the blow gun around...now I can get up 60 psi when I disconnect quickly. I still get a bit of hissing from the barrel, but I still have enough air to launch my nerf dart!

Thanks...I'll tweak it.

Thanks for the comments. OK...I checked a few areas and found 3 leaks....fixed those. I even opened the QEV to clean it out. The gun still leaks from the barrel. Actually, the gun will pressurize up to about 40 psi and when I disconnect the air hose, the gun completely discharges. I am filling from ...

I have built my first copper air cannon using a McMasters right angle QEV. My problem is that when I fill the cannon with air I hear a leak coming from the barrel. Any suggestions?