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What is “Mirage”, what effect does it have on Long Range shooting, and how do we
deal with it?
Mirage can be defined as “heat waves coming from a source of heat, most likely
the sun-heated ground”. We have all seen mirage while driving on a hot day in the
form of the heat waves coming off of a “black-topped road”. Wind moves these
waves — the harder the wind is blowing the faster the waves (mirage) will move.
As such, mirage is also an indicator of wind conditions. However, there are situations
that may prevent you from being able to read mirage (i.e. overcast days, high winds,
etc...). At times like these, the shooter must improvise and use other indicators of wind
condition, (i.e. the movement of tall grass, smoke, or dust, as well as the comments
of other shooter’s spotters).
Mirage can also distort your view of the target. Sometimes changing your front
sight insert will help overcome this and enable you to stay on target. I
would suggest purchasing a copy of “Reading The Wind and Coaching Techniques” by M/SGT James R. Owens USMC (retired) for more information.
It is important to the BPCR shooter that we set our spotting scope to read these
mirage heat waves by focusing on the target and backing off 1/8 to 1/4 of a
turn, counter-clockwise, so we are slightly out of focus with the target but can
still clearly see the mirage heat waves that are present. Ideally the best place
to read mirage would be 1/2 to 2/3 of the distance to the target.
If the heat waves are rising straight up, we say the mirage is “boiling” and the
wind is either not blowing at all or is blowing straight at the spotting scope (head
winds from 12 o’clock or tail winds from 6 o’clock). If the wind starts to
increase while the mirage is in a “boil”, the mirage will change from a boil to
a ragged set of heat waves that will bend or lean, appearing as if the wind is
blowing them away from their source of heat.
If the wind increases in intensity, the waves will become flatter and closer
together until you will not be able to be read them (they tend to flatten out
above 12 m.p.h.). In addition, as the intensity of the wind decreases, the
mirage will slow down and the waves will become lazier and spread farther apart.
These observation examples are assuming that the wind is coming from either a 9
o’clock or 3 o’clock direction. Mirage always appears to travel in the same
direction that the wind is traveling.
Remember that mirage will usually “shimmy” just before it is about to
change. If your spotter sees this condition, he should have you “Hold Off” until
the change takes place or until the mirage returns to the form it had prior to the
shimmy.
Practice reading mirage and range flags together. It will help you make
intelligent decisions about whether to send the bullet on its way to the target
or to hold off and wait for better conditions.
By George Liotta
Copyright© 2010 All Rights Reserved.
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