What are the cons to using 100% CO2 in a pcp? It's an nonflammable gas, but how does it perform compared to regular air? Asking because I have access to it and an curious.
Pure CO2?
- Thread starter BeeGee11
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Co2 will only give a maximum pressure as it evaporates of approx. 800 psi. At temperatures lower than 70 deg F. the pressures are even less so you don't get a very powerful shot capability. If you are looking to hunt or shoot at distances over about 30 yds. you will be woefully underpowered. There are a lot of members here that shoot with co2 and maybe they will have more helpful input than I.
Bruce
Bruce
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Well considering a PCP valve isn't designed to handle a tank full of liquid I'd say your first issue will be liquid CO2 spraying out your barrel when you fire it.
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It won’t spray liquid CO2...the Benjamin Discovery has a conventional PCP valve and overall design, and was marketed as a “dual-fuel” airgun to work with either air or CO2. However I suppose that would be possible if you turned it upside down.
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Atomic weight of nitrogen (78 % of "air") =7
Atomic weight if CO2 = 20
CO2 molecules are huge compared to compressed atmosphere "air". They will move through the valve much slower than pressed air. Helium is way smaller and faster than compressed atmosphere.
CO2 turns to a liquid at very low pressure, limiting how much pressure can CO2 be stored under. Liquids are not compressible. Once it is liquid, you cannot gain any more compression.
Atomic weight if CO2 = 20
CO2 molecules are huge compared to compressed atmosphere "air". They will move through the valve much slower than pressed air. Helium is way smaller and faster than compressed atmosphere.
CO2 turns to a liquid at very low pressure, limiting how much pressure can CO2 be stored under. Liquids are not compressible. Once it is liquid, you cannot gain any more compression.
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Regarding performance, if you compare CO2 and air at equivalent pressure, the CO2 will not produce as much energy. It will be more like 60 – 70% that of air. And like Bruce said, its pressure varies with temperature quite a bit so it’s not the best choice if you need consistent performance over a wide temperature range. Its main strength is getting a lot of shots at fairly low energy which means it’s best suited for long plinking sessions and punching paper. And because of the aforementioned limitations, chiefly at modest distances. Most examples of nice groups you will see on the forums will be at 25 yards or so…very seldom at 50 yards or more.
That all probably sounds like I don’t care much for CO2 but that’s not the case. I enjoy it for recreational shooting in the back yard during warm weather months. Even as someone who doesn’t mind using a hand pump to charge my PCPs, it’s nice to just pop in a cartridge and go, or take a big cylinder and be set for all day fun.
That all probably sounds like I don’t care much for CO2 but that’s not the case. I enjoy it for recreational shooting in the back yard during warm weather months. Even as someone who doesn’t mind using a hand pump to charge my PCPs, it’s nice to just pop in a cartridge and go, or take a big cylinder and be set for all day fun.
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Once upon a time the only reason not to do this was the material of the o-rings. Worst case you will need to upgarde those, then again o-rings are better than they used to be in ost rigs.
And lower power.
John
And lower power.
John
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I am not sure it is a matter of O-rings "are better than they use to ", but that O-rings are made in a number of different materials, designed for the chemicals that will be encountered in the environment that they are being used in. Go down a little on this webpage and see all the different materials O-rings can be made from.
https://www.aceseal.com/o-ring-materials#:~:text=O%2Drings%20are%20mechanical%20gaskets,Rubber%20and%20Fluorocarbon%20(Viton).
You cannot just pull an O-ring out of a hardware plumbing shelf and hope that it will work in all applications. Viton O-rings are probably the most universal material and work with both AIR and CO2.
"RUBBER" O-rings (plumbing) probably deteriorate faster that synthetic.
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Both Viton and Buna-N will swell like mad when exposed to CO2, however I will say from experience that the actual rate of permeation (i.e. loss of CO2) for Buna-N is so low as to be negligible. For example, several times I’ve left a partial 12gr cartridge in over the winter months and pulled it back out in the spring and the POI was still spot on. I don’t know about Viton but on paper it’s supposed to be fine as well. That means they will do fine for static O-rings but you’ll have to make other plans if you have a removable end cap with an O-ring. It will be swollen so you’d want to either use a polyurethane there, or have a spare Buna-N or Viton to swap out (set the original aside for a few hours and it will return to normal size where you can use it again).
BTW a higher durometer reduces permeability, whatever the material, so go with 90 durometer for CO2 when possible.
My personal preference for my mixed stable having several of both air (PCP) and CO2, is to keep Buna-N on hand. Viton swells in the presence of air as well whereas Buna-N does not so that removes one inconvenience. Buna-N also withstands abrasion better for things like bolt O-rings or pump rods. Lastly, Buna-N can be found in almost any conceivable size (inch or metric) and durometer, available from more sources, and costs less. FWIW, I used to favor Viton on account of its shelf life rating but eventually I began noticing that they didn’t tend to last noticeably longer in practice. Your mileage may vary.
BTW a higher durometer reduces permeability, whatever the material, so go with 90 durometer for CO2 when possible.
My personal preference for my mixed stable having several of both air (PCP) and CO2, is to keep Buna-N on hand. Viton swells in the presence of air as well whereas Buna-N does not so that removes one inconvenience. Buna-N also withstands abrasion better for things like bolt O-rings or pump rods. Lastly, Buna-N can be found in almost any conceivable size (inch or metric) and durometer, available from more sources, and costs less. FWIW, I used to favor Viton on account of its shelf life rating but eventually I began noticing that they didn’t tend to last noticeably longer in practice. Your mileage may vary.
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If you have access to lots of co2 why not just buy a co2 gun and be done with it and enjoy it.
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