TargetTalk

Last weekend during the indoor District championship smallbore in the Netherlands the following occured.
After aprox 40 match shots, the POI lowered about 1 scoringring width (5 clicks). First I thought my (prone) position had changed, so I checked but everything was in order. Afterwords I talked to other shooters who were shooting left and right of me. They to experienced the same thing.
During the day, several periods of snow fell occured. Also the air refreshing system blows the outside air straight into the indoor shooting range without pre-heating it.
My question: is it possible that during a period of snowfall the outside air temperature suddenly dropped enough to cause a big enough temperature drop on the indoor shooting range to change the refraction of light, causing an inverse mirage?
(by inviremental law the entire air volume of the range must be refreshed 10 times per hour at an airspeed of max. 2m/s).

Your comments greatly apreciated,
thanks.

Albert B
(The Netherlands)

In my opinion, no way.

Albert,
What distance were you shooting? Cooler air is more dense and will have an affect if you were shooting the less common indoor 50m. distance.

Do the fans run constantly?
If they go on or off the indoor "wind" could have that affect.

I'm grasping at straws.
Ben

I have the same type of ventilation issues at my county range. I am one of only a few who can say they shot an air rifle match indoors at a temperature of 26 degrees.

However, short of a 30-40 degree drop in temperature, I really doubt the cold was the reason for your impact drop. Now it could be explained by your gun warming up. You shooting could have caused a significant temperature change in your barrel that might account for this. But I find it strange that both the fellas to your left and right experienced it the same as you (probably a coincidence). I don't know of too many guns that warm up the exact same way.

I once read an article about inverted mirage. If I remeber it correct, it may occur on a sunny, very cold day with lots of snow, shooting outdoors at long ranges.
In your case, my guess would be that perhaps a spotlight/light bulb above your targets went out, causing a slight darker target and lower impact?