We had a big discussion on this last fall.

This thread was a neat experience to try and we had some decent results.

On a side note, my nets were not big enough to catch a person, and they needed golf balls as weighted points. I REALLY wouldn't want to be hit by a golf ball out of an air-cannon ...

I had considered trying to tap into the barrel and mounting one of my spare weaver rails. That way it can come back off. I have an extra 40 mm red/green laying around. I may try it. Do you think I could make a reasonably accurate ghost ring that can mount on a weaver rail just out of aluminum bar ...

I did consider shortening the chamber some when building it but I thought the look was off. The stock is two chunks of 2*6 so it is about 3 inches thick. Overall I would guess it weighs close to 75 pounds, so shortening the chamber won't save me much weight.

Like I mentioned, I am going to build a ...

How is that valve working? I heard somewhere that they don't open fast enough. I think the person may have just done a crappy job modding it.

Whats more likely is as Maxus mentioned, too small or slow of a release valve. A blow gun is about at small as I would want to put on a 1 inch valve. In ...

I got this guy built last fall late enough I only had time for a few test shots with it last year. This year I have gotten my ranging down and with a full load of 150 psi I can clear a little more than 400 yards. I am currently working on a sighting apparatus of some sort since I can eyeball aim it ...

If you are not interested in using if for any pressure capabilities, ie chamber, or behind the valve, you can use 2 1/2 inch electrical conduit. It is sch 40 cell core. Makes good cheap barrels. 2 inch sch 80 is also available for golf ball barrel sleeves.

You can find it at almost any Lowes, Home ...

You could add baking soda to the concrete powder.

For each cup of concrete powder you mix up, add around a 1/8 teaspoon of baking soda. Then mix with appropraite amount of water. If you really want fast set times, replace water with denatured alcohol (look by the paint thinners). Do not use rubbing ...

I posted this a while ago asking if anyone had used it. Several people had. Here is the thread: My thread

Also see: Spudlings thread

It will run off any paintball tank that I have found so far. This is a really high flow regulator, which demands size. This reg will run a framing nailer at 5 ...

I shall assume you are talking about sch 40.

Ping pong balls are 40 mm (about like the fit of a golfball in sdr21) and can be filled with anything from water to sand to concrete.

Using paper towel tubes you can make pretty effective paintball shotgun rounds or other saboted rounds.

If looking ...

I have had this same leak problem on occasion after modding a few Rainbird sprinkler valves...If you drill and tap your 1/4" blowgun fitting even slightly off center , sometimes this will interfere with the spring seat on the cover of the valve since you drill most of the spring seat away for your ...

Where do you line fnord that 2" costs that much. A 10 foot stick of 2 inch rated is only $4, here.

@pilgrimman

The threads leaking should be on the chamber side if the valve is working properly, add more teflon tape. That sort of thing is common, especially if you have to disassemble your cannon for transport. You shouldn't need to tape the threads on the barrel side. Hose claps should also seal ...

Sorry, I missed the original leak reference. I assume the valve is still set up like in the pictures, with the solenoid still in place.

The leak is coming from, more than likely, one of two places. Either the diaphram is not seating fully, like there is some debris in the way, even the grease might ...

People do use this in cars, but it is mostly in race or high performance cars. A buddy's dad owns a drag strip car and he uses a water atomizer. The engine doesn't run for long enough to get hot, but the extra output really makes a difference.

However, the fuel/air/water is atomized and under quite ...

For combustion:
If you are doing a simple spray and pray, you will fine, If you want to work with metered propane, you should consider returning the pipe for rated stuff. Combustion creates relatively low pressures and not fast or prolonged like pneumatic.

For pneumatics:
People will tell you that ...