Friend had a Wideview on a 8mm Magnum Mauser and his buddy was using it deer hunting. It was sitting across his lap, cool morning, sun came up and when he saw a deer looked into it and the range scale had melted.

Scopes can get hot internally. The issue is who would deliberately allow it to happen if you know it is a problem? Not to forget nobody sights directly at the sun.

Goes to the comment that thermal expansion of the scope from cold to hot - a range of 50F would be typical - and then we take into consideration the tube, lens, erector etc all get larger. Scopes have to have calculated "clearance" to handle it, or parts won't move when it's cold - they will lock into place. There has to be space between components. "Tight tolerances" are not clearances, they are the allowable amount of deviation from a specified blueprint size, because the factory cannot and will not make things exactly. It would cause a much larger number of discards and costs would skyrocket. Take for example, the AR15 - in military form the typical tolerance is =/- .015. I can imagine scope parts being smaller but "tight tolerances" only means smaller allowable variance. Not zero variance - and parts still need to move, there is always clearance or they won't.

If there is a worry about temperature change it's simple to test. Acclimate a scope at 32 degrees at a range, then shoot groups as it warms up. A water bottle, or 12V seat heater, and thermometer/temp gun could do. Test every ten degrees. Watch and see if that particular scope moves which way and how much.

Of course, it needs to be so accurate you can measure to ?? .01 MOA? I would suggest a target at 100m would be necessary, too. Then as the test goes on, the gun needs to continue to keep that accuracy at each temp - if the group gets larger, the scope's drift is lost in the larger change.

This example is likely why we don't see many drift articles or much over it in the shooting press. It's gonna be real tough to document.