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Old June 27th, 2006, 23:41   #1
Delierious Designer of Dastardly Detonations
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Join Date: Dec 2001
Location: in the dark recesses of some metal chip filled machine shop
Madbull adjustable CO2 regulator/adaptor review

I ordered some of Madbulls adjustable CO2 regs/adaptors to try with their land mines.

Basically this product is a regulator body which their original non regulated CO2 adaptor threads onto.

If you remove the knurled top body, there's an ASA standard thread with oring similar to the top of a CO2 tank on the regulator body.

In use, it works well. The integral pressure gauge is a nice one which indicates regulator set point. Unfortunately this is not a relieving reg. If you crank to say 500psi and back off on the adjustment screw, the gauge will remain at 500psi until you vent some gas from the outlet tip. The adjustment knob is easy to adjust carefully. I find it a bit too easy to scrub on gear or bump into things and readust though. I think I'll replace mine with a set screw so I can set it with a hex key and not worry about changing the pressure setting accidentally.

Nice looking adaptor for high pressure Madbull products. Manufacturing quality is very good. Nice bright anodize makes this easy to find on a cluttered table or dropped in the grass. Hunks of CNC aluminum which are well turned are a bit unusual in airsoft so this heavily built product stands out. However there are some significant design issues.

It's unfortunately not useful for anything else airsoft including GBBs as there aren't too many high pressure airsoft accessories. It's actually a hazard for the ill informed who may try to get extreme performance with their GBBs.

I do have some significant complaints about this product:


The bloody stuff is dangerous if you use it at 300+psi in a GBB mag. GBB magazines are clearly not designed for very high pressure. Propane exerts around 120psi at room temp. Unregulated CO2 exerts around 800psi and requires well engineered containers which GBB mags are certainly NOT. Brittle thin walled cast monkey metal in rectangular blocks are a recipe for pipebombs if you fill up with high pressure CO2. I don't even want to think about filling up a GB/Vega grenade gas reservoir with CO2 reg'd to 600psi. Besides, nobody makes hammer springs for an insane pressure regime.

To top it off, CO2 is not a useful replacement in typical GBB magazines. If you regulate CO2 to a lower pressure, you cannot transfer liquid propellant into your propellant reservoir. This means that you only get to transfer gas until pressure in your mag reaches your regulator setpoint pressure. With no liquid transfer, ideal gas laws apply (remember highschool chem PV=nRt?). 500psi is only 33x the pressure of atmospheric pressure (15psi) so a mag filled to 500psi only expands to 33x the volume of the mag when it depressurizes to atmospheric pressure. Conversely, liquid propane expands to over 330 times when it's depressurized to 1atm.

What this means that filling your mags with regulated CO2 will not propel many shots. I used to test GBBs with compressed air from an electric pump when we used to call propane "Green Gas" and it was expensive (I didn't want to use it up troubleshooting GBBs). You can only get about 2 shots with air regulated to 120psi in a mag so I used a fitting which replaced the fill valve so I tested with gas remote.

Separable fill tip module and regulator too easy to remove:

When you want to unscrew the regulator from the tank, it's typical to grab the knurled portion (knurly bits are meant for gripping aren't they?) and twist counterclockwise which would have the knurled portion coming off of the regulator instead of the regulator coming off the CO2 bottle.

The top portion is pressurized to whatever your regulator setpoint is which means that the pressure binding the threads in the fill tip module is lower than the pressure between the CO2 bottle and the regulator body. This means that the friction in the threads in the top portion will be lower than the friction holding the reg body onto the bottle. Because of this, it's easy to accidentally unscrew the fill module from the regulator body when you want to remove the entire device from a CO2 body.

This doesn't result in the top from blowing off spectacularly as a side relief hole starts to loudly vent before you completely disengage the threads. However, it's quite frustrating as the most grippable portion is not useful for removing the regulator body from the CO2 body.

I dislike stressing the adjustment knob while unscrewing this regulator so I spin it out so I can grip more of the reg body. I don't really like bearing on the gauge either, but it's about the only stout protrusion for you to use to untwist the regulator body.
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