Compressed air vs. CO2 for use in AP

[Roly]

I did "Search" the subject and though I found many discussions they didn't address my curiousity. When I got into AP, shooters were moving away from compressed air and switching to CO2, now the pendulum has swung the other way. In fact, when I had my pistol (an LP-10) checked at the CAGP the inspector told me I was the first CO2 pistol "so far" at the match.

I use CO2 in my business and have had a large cylinder in my cellar (a lifetime supply) for a decade. I understand that in some environments CO2 will cause inaccuracies if the pistol gets too cold.

Other than the cost of CO2, and the possible excessive cooling of the mechanism, is there any other reason not to use CO2? Let's overlook the 'greenhouse gas' aspect for a minute because I offset my Steyr's carbon footprint by rarely indulging in carbonated beverages. And when I do I refrain from burping.

[Rover]

"And when I do I refrain from burping."

An Alaskan fishermans daughter once told me; "Always drink beer. That way you get more power behind it when you heave."

Anyway, Pilk has a lot to say on the subject (and he sells the guns). If you have a CO2 gun, you're golden. Don't bother to pursue it further.

[Richard H]

Simple answer is no, unless you shoot in places that have wild temp swings or shoot in extremes of temp.

So enjoy your CO2 there is absolutely nothing wrong with it.

(For the record I own 4 Steyr PCP guns)

[Bugslugger]

Other than the cost of CO2, and the possible excessive cooling of the mechanism, is there any other reason not to use CO2?


I have both a CO2 and a CA pistol. The CO2 pistol hates to be hot. The range where we shoot will sometimes be above 90 degrees F in the summer. The pellet velocity from the CO2 gun will drop to almost nothing but the CA gun doesn't care. I like them both but compete with the compressed air pistol.

[paw080]

Other than the cost of CO2, and the possible excessive cooling of the mechanism, is there any other reason not to use CO2?


I have both a CO2 and a CA pistol. The CO2 pistol hates to be hot. The range where we shoot will sometimes be above 90 degrees F in the summer. The pellet velocity from the CO2 gun will drop to almost nothing but the CA gun doesn't care. I like them both but compete with the compressed air pistol.

Hi Bug, you just need to get the right CO2 pistol! My LP1-C does just great in low 50's to 102 degrees F. I don't particularly like to shoot in
100+ weather but the LP1 doesn't seem to mind at all. I dislike shooting
in the lower temps more than the higher temps.

Tony

[paw080]

dupe...

[peterz]

I've changed to CA from CO2; as far as the propellant is concerned, at any temperature at which I want to shoot, I can't tell the difference. The real reason to change is that more modern CA pistols are far lighter (aluminium tanks vs steel, for example), and the recoil absorption is better. And the grip adjustments are more flexible.

It's the effect of almost 20 years worth of technical improvements in the pistol, not the change of propellant. If you can lift a CO2 pistol comfortably, there's no real reason to change. That said, in 3 months with the LP-10 my score is up 5-6 points on a 10 shot string. But I'm sure it's not the change in gas that's responsible.

[tm255]

i've been told that the CO2 pistols are quieter than CA, sometimes much quieter.

any truth to that?

[deadeyedick]

After owning both co2 and pcp, the only reason I prefer pcp is the easier charging of the cylinder via a scuba tank versus how its achieved with co2.

[jipe]

i've been told that the CO2 pistols are quieter than CA, sometimes much quieter.

any truth to that?

I have the opposite experience when comparing the FWB C25 with the LP10 or K2s or LP300. The FWB makes much more noise than the three CA. The LP300 seems the quieter of the three CA.

Indeed, charging a PCP pistol cylinder is much more easy than a CO2 (no need to cool, to use a scale to measure the cylinder weigth to know if it is really full...) and with modern PCP cylinders with a manometer, you can check whenever you want how much remains in the cylinder while with CO2 you need a scale to measure the weigth of the cylinder. With CA you can also refill with a hand pump, the only solution if you travel by plane and has no access to a big tank after the flight.

But CO2 has the advantage that you can do much more refill with a big tank than with CA and your cylinder can always be completly filled even when the big tank is not full while with CA, the pressure of the big tank drop slowily and the number of possible shots per cylinder also drops. Therefore you need a big enough tank: 5/6l is too small, pressure drops too fast, must be refilled too often. 10l is a minimum, 20l is much better but bulky and heavy.

So, both technologies have pro's and con's.

[deadeyedick]

while with CA, the pressure of the big tank drop slowily and the number of possible shots per cylinder also drops.

This is a little misleading Jipe. Scuba tanks come in many sizes, but 12. litre ..100 cubic feet, is the average and can be filled to approximately 230 bar safely.
The screw on cylinder of a pcp holds 200 bar but the chamber within a pcp air pistol only holds 70 to 80 bar. .
Most people don't realise that the internal chamber of the pistol does not receive 200 bar,and the propellant force is from this reduced internal chamber pressure. I have found the need to top up my scuba tank only once, or possibly twice annually if constantly using the pistol......and that costs me $5 for the top up.
Now, if you buy a 300 bar scuba tank, your differential is even greater, and the number of shots available before top up is staggering.
The chain is...scuba 230 bar slowly reducing ,..AP cylinder 200 bar, on average allowing 160 -180- shots before it reduces to the required 70 odd bar threshold, and Air pistol internal chamber that holds 70-80 bar, and draws from the pistol external cylinder as required.

p.s. I have ransom rest tested my LP10, and found no change in POI until the manometer fell to the lower end of the red, which was exactly what the owners manual said it was capable of. Until that test, I was recharging my cylinder when it approached the yellow.

[jipe]

while with CA, the pressure of the big tank drop slowily and the number of possible shots per cylinder also drops.

This is a little misleading Jipe. Scuba tanks come in many sizes, but 12. litre ..100 cubic feet, is the average and can be filled to approximately 230 bar safely.
The screw on cylinder of a pcp holds 200 bar but the chamber within a pcp air pistol only holds 70 to 80 bar. .
Most people don't realise that the internal chamber of the pistol does not receive 200 bar,and the propellant force is from this reduced internal chamber pressure. I have found the need to top up my scuba tank only once, or possibly twice annually if constantly using the pistol......and that costs me $5 for the top up.
Now, if you buy a 300 bar scuba tank, your differential is even greater, and the number of shots available before top up is staggering.
The chain is...scuba 230 bar slowly reducing ,..AP cylinder 200 bar, on average allowing 160 -180- shots before it reduces to the required 70 odd bar threshold, and Air pistol internal chamber that holds 70-80 bar, and draws from the pistol external cylinder as required.

p.s. I have ransom rest tested my LP10, and found no change in POI until the manometer fell to the lower end of the red, which was exactly what the owners manual said it was capable of. Until that test, I was recharging my cylinder when it approached the yellow.

What I wrote seems to me clear, I didn't say that the POI or velocity changes but well that the amount of shots possible per cylinder refill drops when the pressure drops below the maximum allowed 200bar (or 300bar for the few that allow 300bar). This doesn't happen with CO2 tank that you can use till they are almost empty and always have a completely filled cylinder (at least if you follow the good refill process !).

The amount of time/year you need to refill your scuba tank depends of how much pellet you shoot/year. Note also that many shooting clubs use a scuba (in my opinion much better option than a compressor, less expensive, no maintenance, more reliable) and these should defintely go for a big tank. Note also that besides the scuba tanks, there are also compressed air tanks (there are big models of these, 20l and above, they are cheaper than scuba tanks and are equipped with a DIN thread):

[deadeyedick]

My only reference to POI was to enlighten owners that the yellow, and even red zones on a manometer are still within the 70-80 bar region, and allow complete 100% functionality and performance.
The first point I was making in essence, is that its common knowledge that air pressure in the scuba reduces slightly with every charge of the pistol cylinder, but because of lesser pressures required by the pistol, the reducing amount in the scuba has NO effect on performance until your scuba drops below 70 bar....and that is a LOT of pistol shooting.
The point I felt may be misleading to some is they might beleive the performance of the pistol may be gradually dropping with every shot, and of course that is not the truth, as I have explained.
Personally, I found co2 to work just fine, except in hot weather [ as we have in the Australian summer ] but the convenience in re charging provided by pcp made it a no brainer for me. Having said that, if you are constrained by budget, then the co2 will be as accurate in constant temperatures. But some consideration will have to be paid to POI in extremes of temperature.
In conclusion, I am definately NOT anti co2, but I see a resemblance to drum brakes, and disc brakes. They both work, but engineering improvements has allowed one to work better, and has been adopted as the industry standard.

[toz35]

The only problem I ever had shooting CO2 is when shooting in high temperatures. If the liquid CO2 gets above 87.8 degrees (critical point) it no longer acts as a constant vapor pressure above a liquid and cylinder pressure increases. When the pressure increases the gun usually fails to fire. The mechanisms are not made to function at the pressures found in the cylinder.

This always happened to people who left their guns in the trunk of a car in the sun, sometimes when the outside temperature was only in the high 70's or low 80's. Most of the time if we kept the gun in a gun box out of the sun or a hot car the foam insulated well enough that the temp was not a problem.

All you have to do is bleed a little CO2 which cool the cylinder and remaining CO2 and it will go back to the liquid state and pressure returns to normal. The rate at which you shoot for a match consumes CO2 fast enough to keep the CO2 in the cylinder in the liquid state and the pressures normal.

david