Mirage, wind, barometric pressure, and temperature will mess with your mind. /ubbthreads/images/graemlins/wink.gif
This is where the bench boys earn the big bucks.
I can't give you any kind of formula that would do you any good. Too many variables, including altitude.
There have been a few times I have wanted to wrap a 3000.00 rifle around a steel pole for shooting only a half inch group.... /ubbthreads/images/graemlins/laugh.gif
As was stated above, this is where you keep a log, or make a mental note. If you are shooting at the same place every year, keeping a log that includes the temperatures would help you big time.
Bench guys do not care if they are on target necessarily, they are looking to repeat everything they do with each shot exactly, including paying attention to pressure points, and where their rifle sits in the bags. This will give them the tightest groups. They are not really interested on where the bullets impact on the target as long as all shots stay in one ragged hole.
I would suggest going out to somewhere close to where this balloon shoot is held. Bring a laser rangefinder to verify the ranges and temperatures.
You will learn when to adjust your elevation knob. Heat can play a big factor even if you are keeping things in the shade.
Hope this helps some... -MP
