Friend of mine left his 320 Legion lower, GGI Lockwood upper with a direct milled Romeo 3XL in his trunk in Phoenix for about ten days. Guessing, but temps in the trunk had to be quite a bit higher than the ridiculously hot ambient.
In any event, his zero moved nearly eight inches at 25 yards, both windage and elevation, from his spot on zero that he had at Nationals. While theoretically there could be another explanation, the extreme heat is at the top of the list.
I am wondering what experiences others have had with extreme heat and pistol optic zeroes?