TargetTalk

probably just a physics thing, but anyone else notice that their air pistols velocity fluctuates in temperatures below 40°F?
My home range is currently at 39°f and I two distinct groups 1in above the other....

Hello-

I generally keep my air pistol at 72f/22c degrees; house temperature. Zero is perfect and all is well. If I leave the pistol in the basement range overnight- where the temperature is generally 55f/13c degrees or so- point of aim is off at the start. It usually takes ten, to fifteen shots to warm the pistol up and correct the issue.

When going to a match I try to keep the pistol at 72f/22c degrees, to maintain point of aim. (Less warm up time.) There are some fluctuations with regard to high humidity, and time of year, as well (Ohio weather.)

Best regards!
Brad

Having stood in the driveway with snow falling on me, with an air pistol (and it's usually dark out), I'd recommend this is more a learned behavioral thing, than a "physics" type of problem.

Keep shooting friends . . . .

Not that the grouping changed from hight to low, but that it fluctuated. One shot up, next 2 down, next 2 up, 1 down...not something that I could count on a sight adjustment.. pustol is a 2018 K12.

You would have to put your pistol in a vise to test this. It may well be you that is too cold :)

I would definitely recommend some "anti-freeze."

This research was conducted in Taiwan to determine lethality; it addresses ambient temperature:

http://fsjournal.cpu.edu.tw/content/vol ... SJ12_5.pdf

Why does it have to be the cold and a quick run thru Boyles law.
Why couldn't it just as easily be the viscosity of the lubricants in the
Trigger System changing the stiction in the mating surfaces just enough that we introduce a previously unknown cause for vertical stringing. How we relate to the mechanics of the pistol is a feedback loop of which we have very little solid data to evaluate. The data we do have is normally in a temperature range outside this discussion........

My think on a temperature shift is that in a regulated airgun, temperature is invisable to group size. It the gun sees a change in POI due to temperature, the entire group moves, you dont get stringing. There has been a cause of variablity introduced and a variable process has changed. The gun is NOT variable, it actuates and follows its designed process repeatedly. It may adjust to local conditions, but that adjustment will have a very consistent outcome........

I really think its the shooter interfacing with a trigger with an ever so different feel and us not actuating it the same way shot to shot...... This sounds terribly familiar

Could it be that your trigger finger is too cold.
I personally give up shooting when the temp drops to the low 40s. Because at that point I lose fine control of my ungloved trigger finger.
Sometimes I can barely even feel the trigger, so I have little/no idea of how much pressure I am really putting on the trigger. So I really get the "surprise release." And I do not know how smoothly my trigger finger is working, and am I pulling straight back.
There are too many negative things happening, for me to shoot at that temperature. So I stop shooting about 45-48F.
The primary criteria is how my trigger finger feels; can it feel, and do I feel that I have good control of my trigger finger. If either is no, I stop shooting.

Not knowing your pistol, I can only mention that I found the striker "hammer" of an air rifle that I disassembled was coated in grease and slid in a well greased cylinder. If the grease was at the point of getting stiff from cold, it could be somewhat variable in it's resistance/drag on the hammer. This is a total WAG by me, since I have not done any testing to validate or disprove that thought.

I second Ramon's post on clamping the pistol and testing it.
There shouldn't be any significant vertical spread at 10m.

An other solution is to move somewhere warmer... (written with 30ºC outside... ;)

Hope this helps

Probably just your body not functioning well at 39 degrees F.

Probably... temp is up into the low 60s at night now...