CO2 v Compressed Air

[BobSki]

I apologise if this is a very silly question, but why do pistols use CO2 or "soda-syphon" 12g cartidges instead of compressed air?

My line of thought has been prompted by stumbling across Steve's article on how to make re-fillable 12g CO2 cartridges. I do not have access to the necessary lathes etc he used in his article, so I doubt very much that I would be in a position to avail myself of the advantages he so abley demonstrates.

However, taking his process as an example, why could those same refillable cartridges not be filled with compressed air via a hills/FX stirrup pump or even a divers bottle. Does the CO2 contain properties that make it so much better than compressed air when used in a pistol?

Kind Regards
Bob

[Jerry Cornelius]

CO2 liquifies at moderate pressures at room temperature. Your 12 gram capsule is largely liquid. That means the gas above it will be at a constant pressure for given pressure.

This gives more shots at a consistent and moderate pressure than you can get with air. No pressure curve.

Or that's what I understood. The downside is greater temperature sensitivity, the pressures attainable are not terribly high (and cannot be increased unless you raise the temprature), and I believe the seals are harder to make, as CO2 diffused into many seal materials.

[Linnet67]

CO2 only gives constant pressure for the first 50-60 shots (depending on the gun) from the 12g cartridges and then drops off.

PCP is considered more consistent and is the 'norm' for competitive 10M pistol shooting these days, as you get far more shots from your standard PCP cannister ie plenty to shoot a whole competition.

ATVB
Linnet

[Jerry Cornelius]

PCP is considered more consistent and is the 'norm' for competitive 10M pistol shooting these days, as you get far more shots from your standard PCP cannister ie plenty to shoot a whole competition.

I know that all the top pistols are air now, but I've assumed that is because a bigger cannister and no doubt clever internals overcome the power curve of air?

My PCP rifle will give about 60 shots at good consistency, which makes consistent 60 shots from a little 12g cartridge look pretty good!

I suspect that the real answer to rattycatcher's question is "just because" . When the likes of crosman and co were starting out, I guess it was just easier to produce CO2 cartridges. Now we have dive shops and pumps its easy to get air compressed to pretty high pressures, but by now the 12g CO2 cartridge is a fact of life.

Plus I'm a lot less scared by CO2 at room temperature than I am by air at 200 Bar !

[gingernut]

Brocock made an air cartridge that looks like a co2 capsule. You use an air tank to put 240 pressure into it. You then get 25 higher pressure shots out of your umarex, Works well cost about £25. Must dig mine out and use it more. You do need an adaptor but eventually I suppose you might start saving money!
They may still have them at Brocock.

[gingernut]

PS. you can put air in a co2 gun.You cannot put co2 in an air gun it will wreck it and maybe you too.