12g CO2 cartridge energy in J?

[supak111]

I would love to know much total energy, in Joules is in a typical paintball/airsoft 12g CO2 cartridge?

Thanks everyone.

 

[berkeman]

I would love to know much total energy, in Joules is in a typical paintball/airsoft 12g CO2 cartridge?

Thanks everyone.

What is the volume and the pressure?

 

[supak111]

12 grams of liquid CO2. and CO2 when under liquid under room temp makes about 850psi as far as I know.

 

[berkeman]

12 grams of liquid CO2. and CO2 when under liquid under room temp makes about 850psi as far as I know.

Paintball guns use liquid CO2? I had no idea. I though it was just compressed CO2 gas like my old pellet guns...

 

[berkeman]

A quick Google search shows more info about the cartridges -- looks to be a mix of liquid and gas before the cartridge is first pierced:

http://www.pyramydair.com/article/What_About_CO2_December_2003/6

CO2 and Pressure

CO2 is a gas at temperatures above -69.9 degrees F and 60.4 psig (pounds per square inch gauge). It is a very complex compound with the ability to sublimate (change directly from a solid to a gas without becoming a liquid) as just one of its unique properties.

At 70 degrees F, CO2 obtains a gas pressure of 852.8 psi when confined in a vessel. If there is more CO2 in the vessel, it will be have to be in liquid form. So, the state of CO2 in a pressure vessel, such as a powerlet at room temperature, is a pressurized gas above a liquid. If the gas is released, such as through the operation of an airgun valve, some of the remaining liquid flashes to gas until the pressure is equalized for that temperature.

It's important to understand that CO2 pressure is determined by temperature, not by mechanical compression. If you were to compress gaseous CO2 by mechanical means, it would turn into liquid when the right pressure was reached. The pressure in a 12-gram powerlet remains constant until all the liquid is gone. A powerlet has the same internal pressure as a 10-oz. bulk CO2 tank when both are at the same temperature. Therefore, CO2 guns do not lose velocity as you shoot them until all the liquid is gone and they start to run out of gas.

Also, keep in mind that CO2 is a refrigerant gas. That means it cools when it expands by flashing from liquid to gas. Therefore, when you shoot a CO2 gun rapidly, the gas will cool the gun parts considerably. Because CO2 pressure is based on temperature, the pressure in a CO2 gun will drop if a series of shots are fired in rapid succession. In practical testing, I've seen velocities decrease by more than 100 f.p.s. over a long string of shots. That will affect where the pellet strikes the target unless it's very close to the shooter. So, if you want to shoot accurately with a CO2 gun, do not shoot rapid-fire. With a target pistol, I like to allow at least 15 seconds between shots so the gun's temperature can cycle back to where it was before the shot. But, if you're just plinking, you can shoot faster than that.

Learn something new here at the PF every dang day!

 

[supak111]

Ok so any idea about the energy 1 cartridge holds? even a rough estimate would be great.

 

[d3mm]

As a very rough approximate I have a semi-auto .177 CO2 rifle (Crossman brand, model name unknown) with 12 round speed-loaders. It gets 4 full speed load clips on each 12gm CO2 cartridge before I start to notice a degradation in trajectory. The muzzle energy is 8 ft/lb @ 1.36 joules per ft/lb. This would give 8 x 1.36 x 48 = 522 joules until the pressure of the gas drops to the point where I change the cartridge.

However I suspect the true energy is higher as this rifle seems to waste a lot of gas. There is significant noticeable gas blow back and CO2 smell from the weapon, which does not happen with some other models.

BTW I we are not measuring the actual energy of the gas (that would require e=mc^2) but the usable energy from gas pressure.

 

[supak111]

Yes I was asking about usable energy from pressure

 

[Danger]

This isn't useful to the question, but perhaps of interest. I had a Crossman CO₂ pellet pistol, and so always had a few cylinders kicking about. One time at my friend's place, I wedged one into the latticework of a corncrib with the nipple pointed toward a protected position. From that position (behind a cast-iron cultivator), I proceeded to lay the crosshairs of a 4X scope on a .22 rifle upon said nipple and let loose. All that I saw at first was a massive cloud of fog and dry ice crystals. After a second or so of looking around, my buddy pointed upward, and there was this little silver flash departing the area at about a 60° angle, at least 100 metres in altitude and still climbing. We never figured out where it landed.
Needless to say, I don't recommend this as a home project.