Re: mirage vs light breeze ?
a light breeze will not take the mirage away. I think I know what we are talking about though. You are referring to a no breeze situation where you see mirage with no direction to it. Thats a boil. I can make the target appear to dance in circles. When the wind picks up the mirage lays over or "flows" With that you can see how the wind changes speeds. The only thing is that while you shoot in mirage conditions its causing a light refraction. IE you are shooting at what is not there. If you were zero'd in mirage that was flowing and a cloud blocks the sun out and the mirage " dissappears" you are back to aiming at the actual target. Hence a coming horizontal displacement miss. Its like the pencil in the glass of water thing. Direction of light can also change the optical appearance of paper targets as much as mirage when using iron sights.(I am fairly sure this won't happen with optical sights though I shoot mostly irons in competition)
Now depending on accuracy requirements a boil indicates that you do not have to worry about wind because there is either non or its a small elevation issue as its up or down range in a boil. I'll shoot competition in a boil all day with iron sights and hold a 6 inch or less group at 600 out of a sling.
Personally I like to see the mirage because it gives me an idea of whats going on. And the times I use a scope to shoot with its really simple to see where to hold due to the conditions.
How does it change my impacts? I have not done much work past 300 just to see differences. But testing my best ammo at 300 yards in mirage vs no mirage, 10 shot groups that average around 1-1.5 inches in my service rifle, will expand by close to an inch in heavy mirage.
I would technically prefer a very light mirage(not hot and thick) to shoot at all times. I've been burned badly enough when no mirage is present since you cannot see the changes coming and watch for them. Both in hunting and target work.
Hope some of this makes sense. I feel your pain but, for me, there is no totally perfect answer(other than an overcast, cool day with zero wind and a super rangefinder and accurate rifle)
Get as close as you can, but utilize your skills as needed.