Storing PCP air rifles

I think what is important about where you store you rifle is more around the humidity than the temperature. If the room is dry, I don't see any problem with storing the rifle in 35 - 40 degree temperature. 

I would imagine (can't say why. Other may know.) that one would get fewer shots per fill in the colder weather. 15-18 compared to 25-28 seems like a big difference. Perhaps others can chime in around if that difference is normal or not. 

Chas

I don't know why, but I get fewer shots per fill in the cold. I've not kept track, but this time of year when it's between 0 and 25*F, my shot count is lower.

Gas pressure is a product of temperature and is explained by Boyle's law and Charles' law:

https://en.wikipedia.org/wiki/Boyle%27s_law

https://en.wikipedia.org/wiki/Charles%27s_law

https://www.grc.nasa.gov/www/k-12/airplane/boyle.html

https://www.grc.nasa.gov/www/k-12/airplane/glussac.html

When the ambient temperature is lower in the winter the pressure exerted on the gas cylinder is less. This correlates to less shots than in warmer weather as a result of the reduced pressure by volume.

Storing a rifle with a wood stock in unconditioned space, when cold, can result in a reduction of humidity available in the ambient air. This can result in a cracked wood stock as the wood contracts due to humidity loss.

Cold air is more dense than warm air. I suspect that when pressure is equal whether 90 degrees or 20, the density is different, and this has something to do with the shot count difference. Altitude will also factor into the equation, as altitude goes up, density goes down. So don't forget to correct for altitude difference between examples being compared.

Don't know about the temperature issue. But, (and you probably know this), it should be stored with pressure, but not full pressure. I asked the storage question to an air rifle maker, and he said, if regulated, the rifle should be stored with the pressure below the regulated pressure. Don't know how that translates to a non-regulated rifle, but I guess 100 bar or so might be prudent. 

elh0102, " I asked the storage question to an air rifle maker, and he said, if regulated, the rifle should be stored with the pressure below the regulated pressure. "

Get with some other experienced air gunners and get the correct information. And ask you friend just how you would store your regulated rifle which looses warranty if shot below reg pressure and think about there answer.



Once upon a time the general advise was store anyway you like ( including full) but not dead empty. Most stored full so it's ready to go. Never any issue for decades. A bad batch of Sumatra valves hits the U.S. and one dealer who got hit hard stated NOT full leave them full at all as THIS was what ruined the valve ( not defective material which WAS the problem) and a new rumor was started and taken as fact dispute history.

Good thing it all just for fun eh?



John



John

The reason for storing the rifle at a pressure below the regulator engagement pressure is to avoid prolonged compression of the regulator spring.

The reason for storing the rifle at a pressure below the regulator engagement pressure is to avoid prolonged compression of the regulator spring.

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Hmm, I see your point. But the counter argument to storing a regulated PCP at slightly higher pressure than its regulated pressure is that one should treat the regulator as a "seal" between the bottle pressure vs the regulated plenum pressure. During storage, you want the bottle pressure to be higher so as to create a pressure differential at the regulator "seal", just like how all PCPs should be stored under pressure so as to keep the "seals" pressurized and working. Point here is, you want the regulator to continue "sealing" between the bottle and plenum during storage.

Hence, I keep all my regulated PCPs a couple hundred psi above the regulated pressure.

elh0102, " I asked the storage question to an air rifle maker, and he said, if regulated, the rifle should be stored with the pressure below the regulated pressure. "

Get with some other experienced air gunners and get the correct information. And ask you friend just how you would store your regulated rifle which looses warranty if shot below reg pressure and think about there answer.

John

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John, this was not an air gunner, but a maker of high end precision rifles. Which makers will void the warranty if shot below the regulated pressure? Obviously, you don't want to shoot it empty or near empty, but I don't understand the risk in shooting down to, say 125 bar in a rifle regulated at 135. 

Thank you for your explanation and reply frank320. I respectfully disagree for the reason stated initially but I appreciate you taking the time to explain the counterpoint as well as offer it. I would believe a pressure less than the activation pressure of the regulator would still supply necessary pressure at the regulator and subsequent seals to not fatigue the springs during prolonged compression and thermal changes to the ambient air.

Thank you for your explanation and reply frank320. I respectfully disagree for the reason stated initially but I appreciate you taking the time to explain the counterpoint as well as offer it. I would believe a pressure less than the activation pressure of the regulator would still supply necessary pressure at the regulator and subsequent seals to not fatigue the springs during prolonged compression and thermal changes to the ambient air.

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This is essentially the builder's response to which I referred, "shouldn't make any difference" was his comment.