Heat Mirage At 2°

[SSL]

So - I decided to do some load testing shooting today since the wind was almost non-existent...a condition fairly rare around here. I got all set up and settled in behind one of my rifles, when I suddenly realized that the target was shimmering in my scope making it difficult to clearly see the bullseye.
What I hadn't taken into consideration was that my shooting setup had a little flaw. See - I have a shooting bench set up in my gun room. One of my backstops is 100 yards back from one of the windows in that room. Staying nice and comfy in summer and winter both, it is pretty convenient for moving back and forth between loading bench and shooting bench when working on loads.
Normally this is great, but with the outside temperature at 2 degrees Fahrenheit , the inside temperature at 72 degrees and a baseboard heater pouring heat into the room directly under the window, I had a heck of a heat/cold -induced shimmer where the inside air meets the outside air. I finally figured how to reduce it by putting a sheet of cardboard on top of the bench and extended out the window. That at least calmed the shimmer down somewhat. Still not perfect but I was stubbornly determined to shoot today!
What we go through to work with our hobby!

 

[Walt Krafft]

Long cardboard tube attached to the scope should work.

 

[ricco1949]

We had an evening winter 10-22 Group BR league back in 90's. Shot from inside the club house through designed ports.

Had 16"x16"x8' long plywood waffle carpeted tubes to silence the muzzle reports for the adjacent neighborhood. Many guys shot sub sonic so it was very quiet.

Best remedy for the barrel heat mirage in the tubes was to put a fan in an opposite window facing out. It drew the cold outside air through the tubes eliminating the mirage.

 

[Trigger Puller]

I think his problem was the warm 72 degree room air going out the window into the 2 degree outside environment and causing a heat mirage not the barrel.

 

[JRanum]

Yes, what you are experiencing is the only downside to your set up which what I found when I built my enclosed shooting house. It was -14 yesterday and 70s inside and even with iron sights I get some shimmer. There was a guy on here a few years ago making adapters for Leupold scopes that had mirage tubes attached. He was having the same issues and designed a fix.

 

[JMayo]

I've always called it heat monkeys.... Idk where i got that as a kid. Probably my Pop.