Generating multiple bc from actual elevations

You need version 7.8.6 and newer

Problem Description

At supersonic speeds, the currently used G7 drag model works well. And this (using the 308 Winchester caliber as an example) is at distances of 800-900 meters (depending on the bullet weight).

At longer distances, the calculated elevations often cease to coincide with reality. These differences can be different and depend on the shape of the bullet.

Problem Solution

For the transonic and subsonic parts of the trajectory, use a different ballistic coefficient. That is, two ballistic coefficients.

Practice

1. Let's take the Sierra MatchKing 175 bullet as an example. Select this bullet in the G7 bullet database. Measure and enter into the calculator the initial velocity of 776 meters per second and the temperature at which it was measured.

2. Let's define the distance for our ammunition where the transonic and subsonic zones begin. In the table of corrections, these distances are highlighted in yellow.

3. Let's assign two distances. One should be where the bullet still has supersonic speed. For example, 809 meters. The second - at subsonic. For example, 1230 meters. The speed of sound depends on atmospheric conditions and is approximately 341 m/sec

4. Set the current atmospheric conditions in the calculator

5. Shoot at these distances and get elevations of 9.1 MRAD for a distance of 809 meters and 21.4 MRAD - for a distance of 1230 meters.

6. If for a distance of 809 meters the calculator (BC=0.25(G7)) shows the correct elevation of 9.1 MRAD, then for a distance of 1230 meters - 20.6 MRAD, which does not coincide with the actual elevation at this distance (21.4 MRAD)

7. Let's move on to calculations. Press the "MultiBC" button on the "Cartridge" screen. Now there is only one ballistic coefficient

8. Click the "Create multiple BC" button and enter two distances with the actual elevations.

9. Click the "Calculate" button. We get two ballistic coefficients.

10. Click the "Use these values" button. Ballistic coefficients are entered into the current cartridge.

11. Go to the main screen and make a calculation on the second distance of 1230 meters, where the calculation did not match the actual correction. We see the result. It matches.

Important! Since the actual elevations were measured by scope clicks, it should be borne in mind that the scope clicks may not correspond to the declared ones. For example: click value can be equal to 0.101 MRAD instead of the declared 0.1 MRAD. What can this lead to? To the fact that the calculated multiple ballistic coefficient will work only with this scope! For another scope, it will be necessary to recalculate.