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A tool that is becoming popular for long range
shooters is the "ballistic reticle". It consists of
the normal vertical and horizontal crosshairs plus a series of
horizontal reference bars. In the figure below, a ballistic
reticle with four horizontal reference bars is shown.
Each of the horizontal reference bars can be used for sighting at
different target distances. To illustrate this concept the
following table shows how the Ballistic Plex reticle performs with a
7mm Rem Mag, 140 gr Nosler Ballistic Tip, at 3200 fps.
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Vertical Sight Reference
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Sight In Distance
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+/- 4-inch Range
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Sight-in (Main Cross-Hair)
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135 Yards
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0 to 241 Yards
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Bar Number 1 (1.54-inches
hold-over at 100 Yards
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235 Yards
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0 to 303 Yards
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Bar Number 2 (4.51-inches
hold-over at 100 Yards
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378 Yards
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322 to 419 Yards
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Bar Number 3 (7.52-inches
hold-over at 100 yards)
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500 Yards
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467 to 528 Yards
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Bar Number 4 (11.06-inches
hold-over at 100 yards)
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624 yards
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602 to 644 Yards
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The
Sight In distance in the table above is the exact distance at which the
bullet will strike exactly at the point of aim using the corresponding
reference bar. The data shown in this example was determined by
computing the optimum sight in distance so that Bar # 3 will be right on
at 500 yards. Notice that Bar # 2 is very close to being on at 400
yards, and Bar # 4 is very close to being on at 600 yards. This example
is a very practical configuration for the long range hunter.
At longer distances (Bars # 2, 3, and 4) the accuracy of the sight
reference bar is very important. Bar # 2 will be on at 378 yards, 4
inches high at 322 yards, and 4 inches low at 419 yards. Likewise Bar # 3
will be on at 500 yards with a +/- 4 inch range of 467 to 528 yards. Bar
# 4 will be on at 624 yards with a +/- 4 inch range of 602 to 644 yards.
At shorter distances, the main cross hair can be used to 241 yards where
it will be 4 inches low. Bar # 1 can be used to 303 yards where it will
be 4 inches low.
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The above discussion outlines an optimum sight
in strategy. This coupled with practice to identify target
distances and how to hold between reference bars will lead to a very
useful way for a shooter to adapt to targets at extended
distances. Once mastered, this technique is much faster than
making external scope adjustments.
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Exbal
Ballistic Reticle Analysis quickly performs the calculations that will
help you understand your ballistic reticle and to optimize its
performance. This option has preprogrammed setups for the Ballistic
Plex (Burris), the NP-R2 (Nightforce), and standard mil dot
reticles. Other reticle continue to be added and custom configurations
can easily be specified by the user.
It should be noted that the column entitled +/- 4 inch range
was determined using the Output to Excel feature once an optimum sight in
distance was determined.
The
basic concept is that the program will use the "holdover" value
associated with each reference bar to calculate the distances at which
the bullet will strike a "point blank range" target. The point
blank target is defined by a circle whose diameter is specified by the
user. There is the Zero range at which the bullet would strike the center
of the target. Secondly there is the "MIN" range at which the
bullet would strike at the top of the circle. And finally there is a
"MAX" range at which the bullet would strike at the bottom of
the circle.
The reticle specifications for four different reticles are pre-defined.
The user has the option of specifying any other reticle
configuration. These
specifications consist of holdover values for each bar or dot along the
verticle axis and a units of measure - Minutes of Angle (MOA), Inches per
hundred yards (IPHY), of Mil Radians (MILS).
Finally there are specifications to define the scope being used. They
consist of the maximum power and the reticle location. A reticle located in the first focal plane grows or
shrinks along with image size when the power is changed. This is common
in the Eurpoean scopes. A reticle
located in the second focal plane
stays the same size as the power and image size changes. This is common
in American scopes.
When the second focal plane location is specified, Exbal calculates the
actual holdover values that correspond to the actual (operating) power setting. A power factor is also shown, it is the
ratio of the operating power to the maximum power. (Note: The power
factor can be used to adjust "come ups" computed for the main
cross hair when the scope is not at full power setting.)
There are two optimize functions. The first determines the sight in
distance (main cross hair) so that that a specified reference bar or dot
will strike the center of the circle at a distance specified by the user.
For scopes with reticles located in the second focal plane there is an
additional option to determine the power setting needed so that a
specified reference bar or dot will strike the center of the circle at a
distance specified by the user.
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