Ballistic Reticle Analysis

 

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.

 

Vertical Sight Reference

Sight In Distance

+/- 4-inch Range


Sight-in (Main Cross-Hair)

135 Yards

0 to 241 Yards

Bar Number 1 (1.54-inches hold-over at 100 Yards

235 Yards

0 to 303 Yards

Bar Number 2 (4.51-inches hold-over at 100 Yards

378 Yards

322 to 419 Yards

Bar Number 3 (7.52-inches hold-over at 100 yards)

500 Yards

467 to 528 Yards

Bar Number 4 (11.06-inches hold-over at 100 yards)

624 yards

602 to 644 Yards

 

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.

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.

 

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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