Does temp really matter?

[dwilson050]

Hi all,

Looking to start a little discussion on temperature...

I live in Oregon where it's beautiful in the summer and down right cold in the winter months. My airguns live a cozy life in my garage safe. Because my garage is uninsulated, my safe temperature fluctuates from the mid 50s to the mid 70s with the humidity always below 40.

So here's my question... I'm going shooting on Sunday where the temperature is supposed to be in the high 20s, low 30s. Is it better to 1) just take it out of the warm safe and start shooting OR 2) let it acclimate for a bit out on the range OR 3) maybe take it out of the safe the night before and leave it in the garage to start to acclimate? Maybe there is a fourth option?

Thanks in advance for the knowledge! -Dave

 

[mcoulter]

I do a fair amount of shooting in the winter (both springer and pcp) and whenever possible I do like to let the gun normalize to the outdoor temperature. Given that most of my shooting is casual target shooting, sometimes I do, sometimes I go right out and shoot. 

One thing I would not do is to leave my gun in the garage. Here in the winter time my garage's humidity goes way up as our snow (and salt) covered cars come in and defrost and drip puddles of water all over the place...

Some fun winter pics.

 

 

[nervoustrig]

Assuming you’ve zeroed it at a warmer temperature, you will likely notice a change in the POI at colder temperatures due to the way it influences parts of the airgun as well as the density of the air. If you’re heading out for practice, you can just dial things in on the fly. In which case I’d say do whatever you are most comfortable with. 

However if you were going on a hunt, you would want to characterize it in the cold in advance and then let it acclimate to the temperature the morning before you go out. That way you can be confident of its first shot behavior. At modest ranges (inside of 50 yards) these differences may prove inconsequential but the only way to know is to test.

 

[dwilson050]

Thanks guys. @mcoulter... nice setup you have! Shooting from indoors, I like it! -Dave

 

[Crusher]

I know for certain that when the temps go down, my guns shoot slower and give a poi shift. I see that the pressure has dropped in the bottle and I usually need to bring the elevation up to compensate. Some of that change may be scope and rings related.

So to answer your question, I might put my guns in the trunk of the car overnight. They will be at least close to the temp you are going to shoot.



Crusher

 

[dwilson050]

Thanks Bill, good advice. -Dave

 

[Airgun-hobbyist]

When shooting in the winter I let the gun acclimate before shooting it. It doesn't take long. As far as point of impact changes go, I tune them for the temperature I am shooting in so I don't notice a shift in POI. But as stated by other's above, the pressure will drop in the plenum going into the cold and rise when bringing them back inside after shooting, so you may notice changes in POI on an unregulated pcp.

I get a lot of condensate and even frosting on the barrel and air stripper from the change in temperature of the HPA leaving the barrel, even after being acclimated. So after the shooting sessions I will put the rifle and case opened in front of a fan to evaporate the condensate quickly rather than leaving them in an enclosed environment to stew in their juices and rust. A quick silicone patch down the barrel is also done to prevent unnecessary rusting in there as well. 

 

[qball]

When it’s cold the air is denser and depends on how far the target is the difference could be couple of inches or more lower. 

 

[dwilson050]

Thanks all! -Dave

 

[Jayson]

I roughly factor 1-.5 FPS per deg Fahrenheit. Seems to be close in my chronographs. Just what works for me,

 

[lloydf]

Shot this morning in relative cool conditions, gun came from warm house and I noticed a pretty good POI change. Throw in VERY thick smoke from the Cali fires and I found the air to be very thick and what would be called "heavy". I have never shot in thick smoke before but in my opinion it sure raises hell with everything. We aren't going to die from covid here, it's going to be lung cancer from the daily smoke for the last month!

 

[Smitty8141]

I notice, like Jayson, about 1 fps slower per degree of temperature drop If you have sighted in the gun during summer, you will notice a fair drop in colder temperatures. It is more noticeable the far the shooting distance. 

 

[Blackpaw]

Yes, one thing we can’t get around is the laws of thermodynamics! Aka Mother Nature’s influence on our lives and our toys/tools/whatever you want to call it!

I would say the two biggest things that influence your POI is altitude (pressure) and temperature, and less humidity, and the further distance you shoot the more likely you’ll notice the change in POI. I look at it this way, your car/truck tires require a certain amount of recommended pressure (PSI/BAR) to work correctly, when it is winter (5 C/40C) more air is needed to get the same pressure fill than when it is 35C/90F out.

Personally, I would think your efficiency (use of air / shot) goes down in the winter due vs summer months vs “ideal conditions” where I feel most companies do their testing data.

If possible I would love a company to do a winter vs summer shot count figures, but I doubt that will ever happen, and I mean places that have real winters where it snows half the year

 

[nced]

Personal opinion based on HW95 & Beeman R9 break barrel spring piston airguns used during field target matches but I have no first hand idea about PCPs, however I'm assuming that even atmospheric conditions will affect pellet flight. I know some field traget shooters that even had "tape aquarium thermometers" attached to their SCOPES and had different numbers on their dope sheet based on the temperature because they claimed that temperature variations affected the SCOPE itself and it's range finding abilities and the poa.

For my spring piston airguns, temperature does make a difference, and how much difference has a lot to do with the piston sealing and lubing. Decades ago my brother and I were squadded together for an early spring field target match neas Harrisonburg, VA and our sight-in was done during snow flurries. About 3/4 way through the match the temps rose from the low 30s to the mid 50s and during that shift both my brother and I were getting a lot of unexplained misses. Out of curiosity we both shot at a "ground level leaf" about 20 yards away and found that our poi had shifted 2" at only 20 yards.

After the match and returning home I disassembled my R9, stripped all existing internal lube (spring tar on the spring, molly paste for the piston seal) and then relubed with a very thin coating of only molly paste. This didn't completely address that temp related poi shift but it was reduced considerably. Thinking that the "poi shifting issue" might be the changing durometer of the "rubber" piston seal and the viscosity of the internal lubes (especially the spring tar) due to the temp. Well, I went to an Ace home center and bought a couple 1" nitrile orings, cut a piston cap from some 6061 T6 aluminium rod, cut an oring groove in the cap and fitted the oring. LOL......this mod increased my velocity 40fps with the same internals and I noticed that it only took a couple shots to "settle the zero" instead of about a dozen shots required for stabilisation with the factory seal.

Anywhoo.........."atmospheric related poi shifting" can only be compensated for, however the degree of "mechanical related" poi shifting MIGHT be reduced.

 

[nicecue]

Very interesting discussion, my first winter shooting in WI. I'll have to check it out.

 

[tsmith]

i notice more poi shift in the heat. my poi is way high when the sun heats up my gun. frustrating.