How To Change a Gun's Sight Adjustment
Many ballistic problems require you to change your gun's sight adjustment to another value. To change the sight adjustment to another value, you need to know what direction to turn the scope's elevation knob and how far to turn it.
Direction: If the sight adjustment value is smaller for the range you want to go to, the elevation knob must be turned in the DOWN (-) direction. If the sight adjustment value is larger for the range you want to go to, the elevation knob must be turned in the UP (+) direction.
How far: To determine how far to turn the elevation knob, subtract the smaller sight adjustment value from the larger sight adjustment value. The difference is the number of MOA the scope's elevation knob must be turned through. The actual number of clicks depends on how many clicks per MOA your scope has. If the difference is 2 MOA and your scope has 4 clicks per MOA, turn the knob 8 clicks (8 = 2 x 4).
Example: For a given load the settings at 100 and 250 yards are 4.3 and 8.4 MOA, respectively. The difference between these two settings is 4.1 MOA. If the scope has 4 clicks per MOA, the elevation knob would have to be turned 16 (16 = 4.1 x 4) clicks in the UP direction to change the zero range from 100 to 250 yards. Once you've adjusted the elevation knob, you should test fire the gun to verify that the bullet is zeroing at the correct range.
If the zero range is too large for the range facilities you're using, test fire at a shorter range, like 100 yards. Aim for the bull's-eye and fire a group of five shots. Compare the actual height (above the bull's-eye) of the group's center with the value predicted by the program. Adjust the elevation knob to move the group's center to the predicted height. Fire five more shots to verify that the center of the group is at the predicted height above the bull's-eye. This is the same method that's used to zero a gun at a particular range, except, you want to center the group at the predicted height rather than at the bull's-eye. Zeroing to a predicted height is not as accurate as zeroing to the actual range, but it's far better than not test firing at all.
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