Over the past few years I’ve received this request a few times, the gist of which is the following.
“I’ve been shooting 100 yards and I wanted to try 500 yards. I looked up the (whichever-manual) drift and drop charts for my load and bullet and saw that there was an X-inch drop from 100 to 500. I adjusted for that and I am way over the top of the target. What am I doing wrong?”
You need to think MOA (Minutes of Angle) and not inches. MOA is an angular measurement. It’s 1/60th of 1 degree (360 degrees in a circle). Thus, 1 MOA spreads about 1 inch per 100 yards (it’s precisely 1.047 inches. Since it’s an angular measurement and not an empirical one, 1 MOA is a different size at different distances. Multiply or divide to get the right answer for your distance.
For example, 1 MOA at 100 yards is 1 inch, so at 400 yards 1 MOA is 4 inches. What matters is getting the come-ups (elevation adjustment from one distance to another) in MOA. Or, if the chart is in inches, then divide by the distance multiple and apply that to the sight. If there is a 20-inch drop from 100 to 400, the 400 distance multiple is 4 so divide the 20 inches by 4, get 5, and that’s how many minutes of adjustment to put on the sight—and then put on the elevation in MOA. If it’s a “quarter-minute” sight (4 clicks per 1 MOA movement) then it’s 20 clicks. That also means using the same 400-yard point, one click on the sight at the firing line results in 1 inches movement on target. So, divide or multiply by the distance multiple depending on what you’re needing to know.
Read more: Making Sense Of MOA