Here's how it works: First open the 3-way valve so that the pressure pump is open to the chamber behind the piston. Use the pump untill the piston shoots forward and the sear catches onto the middle set of washers. Pressurize the chamber through the inlet at the bottom forward end of the gun (I plan...

Do this to solve your problem:

I would get some rod material like nylon, UHMWPE, or Delrin and just cut a section of it to suite your needs. As for the sealing face, glue a circular piece of sheet rubber to one side. I also suggest hot glue, because they already come in 1/4" rods. Just take one and cut it. I think it is soft enou...

What I like about this gun is that you can get the majority of these parts from places like Home Depot and it doesn't require (at least to my knowledge) any special machinery like a mill or lathe.

I am making a high pressure pneumatic air gun and the chamber is made out two 1/2" brass tees with a 6" nipple between. The threads are going to be the weakest/leakiest part, but I have soldered the threaded joints as opposed to using PTFE tape. Soldering the threaded joints seemed to work very well...

I am making a 1/2" QDV airgun and for the chamber I have used 1/2" threaded brass fittings consisting of two Tees and assorted bushings (the overall length of the chamber is 4-6 in.). I plan to take it to a pretty high pressure with the on-board hand pump. Somewhere around the neighborhood of 800 ps...

I wouldn't take it to 2x. MoonBoggs's cannon: http://www.spudfiles.com/forums/the-cobra-venom-t17948.html has a 4"ID chamber made of sch10? aluminum and he isn't comfortable with igniting it at a 3x mix. I think a .188" thick 6" chamber would not be as strong as the Venom's chamber because of its in...

Our metering system needed an auxiliary tank to support the added fuel needs.

Ha!

I can't wait to see this thing in action! I do have some advice though. When I built my 2.5" QDV tennis ball launcher, (4" PVC chamber coaxial never posted because trigger handle broke) I found that materials such as solid plastic had too much inertia and blew the back out of the cannon on the secon...

The piston will allow enough airflow for filling without the hole as long as it isn't extremely tight in the housing like hydraulic tube.

Let me guess, the big piece of PVC pipe that the gun is strapped to is the on-board precharged air source. Is there any reason why the vortex cap and barrel are inside of a soda bottle? My suggestions are to do away with the soda bottle and if you are serious about this gun, get a CO2 source or a mo...

If you have a plumbing supply company around you that does commercial sales, it is possible that they have a will call center that you can just walk into. This is that kind of place where you might be able to find SDR-21 (perfect fit for golf balls) and sleeve it into 2" Sch 80 PVC. You probably alr...

I think that there is something more to it than a small diameter. For instance, if the cylinder was only 0.5 inches in inside diameter (I think that the pumps are wider), the force needed to compress the pump at let's say 3000psi would be 589 pounds. I hope nobody here weighs that much. That's a fun...

I have always wanted one of those floor pumps that are capable of filling an HPA tank (with a lot of work), and I always wanted to build a homemade one, but I can't figure out how the 3600+ pressures are reached with a sizable cylinder diameter (.75-1 inches). I think it might have something to do w...

I have been thinking about making an gun similar to the XM2. I want it to mimic the actions and looks of a pellet gun, but be in a greater caliber such as 0.5 inches. I was originally planning on making a miniature QDV for the gun (I have made a 2.5" diameter QDV in my 4" coax and I love them), but ...