ORIGINAL: Underclocked
Tie a helium ballon centered over the bull at the right height to allow for drop. Be a good wind gauge as well.
Not a bad idea. I actually have some helium in the garage.
I'm going to check the scope travel tonight. I recently purchased a good Nikon spotter for my upcoming elk trip that should be able to spot holes from at least 300 yards, so that will save me from heat stroke checking targets....