If you shoot a rifle match with a long string of fire, you’ve most likely encountered a mirage caused by a hot barrel. At best, it makes shooting more difficult requiring the scope’s magnification to be decreased, at worst, it can obscure your sight picture to the point of costing you points.
My buddy showed up to a match with his 223 rifle and an improvised mirage band. I couldn’t help but laugh. A little electrical tape and some cardboard and he had a workable solution. It might not look great, but it worked!