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Jaxom · Senior Member

We've all discussed in here often how the cold affects air guns and their performance. I've had first hand expiernce with this, when attempting to take a squirrel in my back yard once the temps dropped below 40F. Granted I was inside and out of the wind. The rifle, (my 1077, Co2 charges) are stored in my bedroom. I thought I wouldn't have a problem, but when I went to take the shot, pellet basically went about two feet and dropped like a rock. Later I tested the whole thing in my basement where I was shooting indoors. Worked as usual.

So, okay I've reproved a point we've already discussed. Shooting a Co2 powered air gun doesn't work well in the cold.

Now, last night, I was in a chatroom. I've a lady friend that lives in central Ausstralia, whom is into target air pistol shooting. Now she's claiming that when the summer time tempuratures exceed 100F, that her air pistol doesn't shoot very well. I some how have a hard time believing this. It would seem to me the colder/denser Co2 would expand even more at higher tempuratures.

My theory would be, hotter air would be less dence. As the Co2 rapidly expanded the pellet would feel less resistance from that surrounding air. The only limiting factor would be humidity. Higher humidity, like that experinced just prior to a major weather front could possibly affect how the pellet travels negativly.

About the only other thing I can think of is the warmer tempuratures have cause parts inside the pistol not to correctly function, causing the poor performance.

I don't recall the brand or model pistol she had. She did say once that it cost her $1500 AU about 5 years ago, and that it was made in Germany.

So, what's your thoughts and or comments?

Jax

rsterne · Moderator

CO2 exists as some liquid and some gas at "normal" temperatures (below 88*F).... as the temperature increases, so does the vapour pressure of the gas in the cylinder.... cooling is the reserve....

If you are talking about a Springer, or a "Pump & Dump" pneumatic, then at higher temperatures the air is less dense, and in theory you might get poorer performance at higher temperatures.... I say in theory because I have never observed this....

If you are talking about a PCP, then it would depend whether it is a regulated design or not.... If non-regulated, then it would further depend on the temperature at which is was charged.... If charged at high temperature and allowed to cool, the pressure would drop.... if charged (very slowly) at low temperature and then warmed up before shooting, the pressure should increase.... I have observed a Retained-Air Pumper losing pressure (and velocity) when allowed to cool.... Please note I am NOT talking about it leaking, simply the temperature effect....

Bob

Alstone · Moderator & Site Supporter

I find that my Co2 Rohm when left in a hot conservatory 100 deg for a while, the valve locks up with the high pressure and as Bob says when the tempreture comes down below 88 deg things return to normal.

Al

AirGunEric · Site Admin

That is it- beyond a certain pressure point (let's use 88*F) the Co2 has expanded so much most valves in airguns designed for Co2 use can't operate properly- either the valve locks up or opens a lot slower.

Look at the calculator to see what sorts of pressures the Co2 is at at different temperatures:

http://www.airgunhome.com/pages/calculators.html

At 68* Co2 vapor pressure is at 833psi, at 87* it is at 1058psi, at 100* it is at over 1200psi which is also the point where most people consider a typical airgun Co2 valve to lock up.

fritz · Silver Status Member

Good reason to go HPA.

Jaxom · Senior Member

Thanks for the wonderful explaination Eric! That make perfect sense to me now as to why her pistol won't work in mid summer temps. But now, I've a few more question re bulking my 2300. Two different topics, I'll take those questions back over to that thread.

AirGunEric · Site Admin