TargetTalk

This is clearly not a competition gun, but should provide greater accuracy for 10 meter shooting than my spring-air rws 34. Anyone own one?

Also, this precharged gun is "dual fuel" co2 or ca. I am curious about the pros and cons of ca and co2. The idea of filling from a 20 oz paint ball tank seems to be logistically easier.

Also, why would one of the 2000 psi dual fuel guns get many more shots for a filled reservoir of co2 than ca? I realize the velocity would be lower on co2, but this is not a concern for my indoor shooting.

Thanks for any comments.

you get more shots per fill of CO2 vs CA due to the fact that the CO2 in the reservoir is in liquid form. You store more energy per liquid measure of CO2 than gas measure of high pressure air.

The CO2 guns would rely on the fact that below a certain temperature the CO2 would be part liquid and part gas. In Thermodynamics of Materials there is something called a critical temperature above which a material cannot exist as a liquid. For CO2 this is somewhere in the high 80s Fahrenheit. While on a cool day you could use the temperature of the CO2 as a natural pressure regulator as things warmed up the pressure would increase or if you passed the critical temperature the pressure would go unregulated (and the gun would often just go whacky). For precision shooting, CA offers much better pressure control.

'Dude

Interesting. What temp range is suitable to use co2 guns? Appears that 85 degrees far. is the upper temp?

Lammy,

It is tough to put an exact upper limit on the operating temperature of a CO2 gun. First, the critical temperature is 87.76F so clearly, without a pretty fancy regulator (fancier than those used for the PCP guns) above the critical temperature, things are not going to go well for a CO2 gun.

First thing to consider, when I say liquid CO2 and gas CO2 most people think of the difference between water in a glass and the air around it. This is a clear sharp difference, water is about 1000 more dense than air so the two separate quickly and the line between them is clear.

Now CO2 is a very different beast. at 75 degrees F, a vessel with CO2 in it, the liquid is only 3.1 times denser than the gas. If you watched the liquid "sloshing" around it would be like the old "wave" toys with two slightly different oils in the clear container, everything happens in slow motion. Without the sharp density difference it is easier for liquid to flow into places where liquid should not be.

Now at 80F this density ratio is about 2.5 and at 85F it is 1.7. This ratio decreases to exactly 1.0 at the critical temperature where I can no longer tell the difference bewteen the gas and the liquid.

Next, different guns are going to show different sensitivities to the fluid phenomenon of CO2. Frankly, for precision work I would not want to shoot CO2 much past 68F (liquid to gas density ratio about 4) for just messing around 80F might be the limit of reliability.

Another thing to be aware of is the rising pressure. As I noted in my first answer the liquid/gas interface of the CO2 created a natural pressure regulator. Great, this regulator changes setpoint with temperature:

68F = 831PSI
75F = 912PSI
80F = 970PSI
86F =1046PSI

Overall, precision CO2 guns are an interesting and practical idea but best suited for cooler climates and more recreational instruments. (I started to study this problem after a Feinwerkbau Mod 2 CO2 air pistol went nuts on me, in a match, while I was living in southern Texas) I was also verbally abused at one point in the late 80s (the zenith of the CO2 powered precision guns) when I was discussing this problem and some father in earshot thought I was diss'ing his daughters and their new FWB C60s.

Probably more than you wanted to know but hey... you asked. : )

Cheers,
'Dude