Fascinating video! Great series Philip! Lot's to think about and experiment with.

Aluminum is a very good transferor of temperature. Heat and cold will pass through it and radiate onto the surface of any metal surface within the scope very quickly. The nitrogen will help to reduce the effect better than any other material that is currently available. However most scopes are also black or darker colors which also absorbs the heat faster than light colors. As far as the rifle goes it can also cause some problems with temperature transfer into the internal environment of the weapon. Such as lubricants and seals which will thin out or become softened with heat or the opposite during colder periods. On a piston driven rifle these differences although miniscul can be enough to cause the weapon to shoot different during a series of fireing cycles. It just depends on your individual weapon and how much time you spend on testing. Just my thoughts on it.

i set my Daystate Wolverine .177 HFT rig up with Sightron S-Tac 4-20x50 ffp up in 68 degree weather in my heated and cooled garage. When i shot at Baton Rouge temp was 38 degrees when we started... everything was off until the temp rose to about 46 degrees. @Brian V - thanks for that jewel about the across the board affect being the gun rather than the scope.... totally makes sense now! Shift happens. It is interesting that the major manufacturers of scopes haven't put this kind of info/data out for people using their products... rain like you operate, operate like you train. Ideally with a mag wheel you could have three or four different wheels set up in the different temp ranges, 45-55, 56-65, 66-76 and 77-95? Or 3D printed rings that clip over the wheel that were pre-marked for different temp ranges. Question - I experience 2-3 temp shifts that are scope related - what about others?

In the UK I use a March Majesta and once it got down to 4 degrees n below 6 clicks were needed at anything over 25 yds. And the same over 28 degrees.

Great topic, interesting discussion on whether power of scope makes a difference. My uncle uses a Smidt and Bender variable to 80x. and has a 7" range finder wheel. He has 3 different interchangeable range tapes for various temperatures. If I remember correctly, he said the deviation was constant between yardages at the temperatures the tapes are calibrated for, just a different offset for the zero point. Higher power scopes, I suppose, would have thicker lenses with more curvature. Am curious how that might affect the focal point when range finding. The coefficient of thermal expansion for aluminum and glass can differ slightly according to their alloys and type of glass. Thicker, high power lenses might take longer to acclimate to external temp changes.

excellent video. One question, do you use shooting glasses? Why? Thanks