How about CO2 in a PCP gun?

[tenex]

Everyone seems to be talking about pumping their CO2 guns up with air, how about the opposite? What if I put 40 grams of CO2 into a PCP air pistol cylinder? The regulator shouldn't mind (as long as liquid CO2 stays out of it), and most of the PCP guns are the same as their CO2 counterparts (my assumption).

According to my calculations, I should get the same useful number of shots from a 5 lb CO2 bottle as an 80 cu. ft. scuba tank filled to 200 bar and used down to 150 bar (to allow at least 100 shots per refill).

Just thinking out of the box. Any opinions?

Steve.

[Tycho]

One thing that comes to mind is the temperature - CO2 sealing rings have to resist cold, pressurizes air seals have to resist heat. I remember Hammerli having some problemes in that department with their earliest 480's and changing the material after that. And I'm not sure if the pressure of the CO2 would be high enough to open the valve into the reduction chamber. Otherwise, I'd guess that it's at least much less dangerous than filling CO2 pistols with air.

[David M]

No, it won't work.
Air pistols work with a tank pressure starting as high as 200 bar (3000 psi) [Note some up to 300 bar- chech your cylinder] and use a reducing valve to modulate the pressure to approx 80 bar (1100 psi) for each shot.
Co2 pistols work on the principle of converting a liquid to a gas at a constant pressure (Reid vapour Pressure) ie as you reduce the gas pressure the liquid boils to produce more gas. In your pistol this happens at about 70 bar (980 psi), hence the fill pressue is to just above the critical pressure of 73 bar.
It will not work for any lenght of time without the liquid CO2.

[tenex]

No, it won't work.
Air pistols work with a tank pressure starting as high as 200 bar (3000 psi) [Note some up to 300 bar- chech your cylinder] and use a reducing valve to modulate the pressure to approx 80 bar (1100 psi) for each shot.
Co2 pistols work on the principle of converting a liquid to a gas at a constant pressure (Reid vapour Pressure) ie as you reduce the gas pressure the liquid boils to produce more gas. In your pistol this happens at about 70 bar (980 psi), hence the fill pressue is to just above the critical pressure of 73 bar.
It will not work for any lenght of time without the liquid CO2.

I do want to put liquid CO2 in, just not so much that it runs into the regulator (like a conventional CO2 cylinder). I'm thinking that if I can get a conversion kit to run CO2, why not just fill the air tank and run it through the regulator. This does assume that all the conversion does is remove the regulator and swap the CO2 tank for the air tank.

Steve.

[Richard H]

One really important thing, you are dealing with pressure vessels, if you don't really understand how they work and from your post its pretty clear that you don't, I would not recommend screwing around with them, for fear of injuring yourself or someone else. If you want to shoot CO2 get a CO2 conversion kit or a pistol that comes prepared to shoot CO2.

[jipe]

One really important thing, you are dealing with pressure vessels, if you don't really understand how they work and from your post its pretty clear that you don't, I would not recommend screwing around with them, for fear of injuring yourself or someone else. If you want to shoot CO2 get a CO2 conversion kit or a pistol that comes prepared to shoot CO2.

Good to remember Richard: people should never forget that these thiny, colored cylinders of CO2 and PCP pistols are dangerous things that should be handled with care and according to the manual !

[David M]

Yeah, some day some idiot will blow themselves up by trying to fill an old CO2 cylinder with 200 bar air. Good thing that the fittings are different.

[Tycho]

That could ruin somebody's whole day... seen the impact crater in the roof where a Morini manometer blew out of a (very early series) pcp tank...

[tenex]

One really important thing, you are dealing with pressure vessels, if you don't really understand how they work and from your post its pretty clear that you don't, I would not recommend screwing around with them, for fear of injuring yourself or someone else. If you want to shoot CO2 get a CO2 conversion kit or a pistol that comes prepared to shoot CO2.

Gee that's a bit harsh, I guess I should try to get my money back for that engineering degree. FWIW, Benjamin is doing exactly this in their new Discovery rifle:
http://www.airgunsbbguns.com/Benjamin_D ... 1k77gp.htm

Does that make the question any less stupid?

That's the beauty of the internet, you can ask a question even if you're not actually going to do something.

Steve.

[Richard H]

One really important thing, you are dealing with pressure vessels, if you don't really understand how they work and from your post its pretty clear that you don't, I would not recommend screwing around with them, for fear of injuring yourself or someone else. If you want to shoot CO2 get a CO2 conversion kit or a pistol that comes prepared to shoot CO2.

Gee that's a bit harsh, I guess I should try to get my money back for that engineering degree. FWIW, Benjamin is doing exactly this in their new Discovery rifle:
http://www.airgunsbbguns.com/Benjamin_D ... 1k77gp.htm

Does that make the question any less stupid?

That's the beauty of the internet, you can ask a question even if you're not actually going to do something.

Steve.

Not really I looked at the that ad all it really talks about is using 2000 PSI

All but one match airgun uses 3000 PSI {200 BAR}(walther is the only one that uses 4350 PSI {300 BAR}).

The specs say PCP and CO2, but it really seems unclear if you use the PCP components or is there some adapter.

As for being an engineer, thats great but you're explanation above didn't give me any any confidence that you knew what your were talking about. Then there are lots of types of engineers, and every engineering degree doesn't make one an expert in every subject.

As for it being harsh, it might be, but look at it from this perspective; some idiot modifies his air gun and it fails and kills himself or worse some innocent person (maybe a kid), the next thing that we'll hear is the cry of banning air guns because they are dangerous. All this because someone doesn't want to pump up a cylinder, get a scuba tank or get a CO2 pistol.

[556]

If you want to shoot CO2 get a CO2 conversion kit or a pistol that comes prepared to shoot CO2.

I know conversion kits FROM CO2 TO PCP are available from Morini (and Steyr?)
But have never heard of any "retrofit" conversion FROM PCP TO CO2.
Is any such device available for modern PCP guns?

[pilkguns]

You could retrofit a pistol back to CO2 that was already upgraded to CA, by replacing hte regulator with the old cylinder mount, but you can't make CO2 work in a unmodifed CA gun because the pressure differential is too great.

The Crosman Discovery is an unregulated gun, and thus with some spring tweaking can be made to run on either. It is the basis for the BF-17 we are builiding.


Shrek, I modified your post to put the correct pressures in there.

[Richard H]

Thanks Scott, that's one reason I wouldn't screw around with it ;)