OK, let's do this right. I used a 2 pound, ABC Kiddie Brand, disposible-one time use, non-rechargable, kitchen/boat fire extinguisher body.
I get them for FREE or $2 at my local fire extinguisher supplier. They salvage the dry chemical if it went flat and lost pressure and sell the aluminum body for scrap. Found two dead ones at garage sales for a quarter each. So are CHEAP and plentiful. Go to LOWES and buy a brand new one for $25.
According to a Tech, Aluminum Fire extinguisher bodies splits under pressure and generates little or NO schrapnel. They decided to shoot a couple of outdated but pressurized ones with a rifle just to see what happened. (He may have left out the 'drinking at the time' part.) Bullet holes with a split. So I doubt an application in paintball would be much more abusive than that.
The fire extinguisher body weighs considerable LESS than an equal volume air chamber made out of PVC Pipe which DOES turn into schrapnel when they fail under pressure.
Below was a staged failure to illustrate WHY you may not want to use PVC for an air chamber. 150 psi shot with a .22 rifle.
So it is CHEAPER, SAFER, LIGHTER to use these readily available fire extinguisher bodies than "old school" PVC pipe to make air chambers for Nerf cannons and bazookas.
Below is the pic of cutting off the stock nozzle. It is a reinforced PLASTIC fitting. You have to disassemble the valve and remove all the metal parts first and then I screwed the empty nozzle back onto the body to hold it true and square when I cut it off with a table saw.
Below is drilling the hole for the tap. That spade bit I ground down to the profile I needed for the tap. I didn't have the drill bit and if I did, didn't have a drill press big enough to hold it. So I fudged.
Here's a pic of the ground spade bit.
Below is tapping the 1/2" NPT into the drilled Nozzle Fitting of the Fire Extinguisher. Put the tap upside down in a vice and used the fire extinguisher body for a handle. Worked. More fudge factor.
Below is the 1/2" NPT nipple with NO untreaded shoulder on the LEFT. You can see the nipple on the RIGHT is too long for the final fitting to seat onto the neck of the fire extinguisher but you COULD just screw it into your valve fitting.
Below is a reducer fitting 1/2" NPT to 1" NPT to screw directly into my 1" valve fitting.
In the Shorty picture below, the 1/2" nipple is screwed directly into that 1/2 NPT 4 way / Cross fitting and seated on the shoulder of the fire extinguiser body for extra mechanical strength.
I just wanted it mechanically REAL BEEFY for the abuse on the field it has gotten. It has been banged around for 4 seasons without a hitch.
I used a pipe extractor tool to screw that shoulderless pipe nipple into place with some BLUE Loctite on it. Then put the reducer fitting on with Blue Loctite on it and screwed it down TIGHT onto the neck shoulder of the body. Let them BOTH set up over night before assembling it further.
Below is an illustrated pic of the Shorty.
You must have a pressure guage and a pressure relief valve. The one seen is 150 psi.
Paintball regulators DO fail.
The one on my Shorty saved my bacon ONCE. I was using a dual regulated paintball air tank (4500 psi) with the second stage output at 145 psi. It was trying to match the air tanks internal pressure at 4500 psi but very slowly. The pressure relief valve would fart about every 4-5 minutes. Figured it was just the hot day and the reg output maybe just a tad high. Went to check it and noted the pressure guage creeping up slowly. Then I remembered that I blew a remote hose using that tank with a marker. Used my spare and it blew too. NOW I knew why..... A Bad reg on that air tank. Without it on my Shorty, a 300+ psi explosion would have happened in the staging area with a bunch of people around without masks on.
NOW I turn off my air supply and discharge any pressure before entering the staging area... Double safe. Just in case........