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Sighting in a firearm with a telescopic sight

The adjustment controls of a telescopic sight with an elevation adjustment knob featuring a zero-stop and second revolution indicator.
The adjustment controls of a telescopic sight with an elevation adjustment knob featuring a zero-stop and second revolution indicator.

When sighting in a rifle equipped with a telescopic sight, make sure you are familiar with the scope’s adjustments. The two primary adjustments are the elevation adjustment knob on the top of the scope’s tube, and the windage adjustment knob which is usually situated ninety degrees to the right of the elevation knob. These knobs are typically protected by screw on covers that have to be removed before the scope can be adjusted.
Most scopes have click adjustments, each click of the adjustment representing a certain amount of change on a bullet’s point of impact. The most popular amount of adjustment on hunting scopes are  quarter inch clicks. That means that each click represents a quarter inch of bullet impact change at one hundred yards, four clicks equaling one inch at one hundred yards. At fifty yards, because you are closer, four clicks would move the bullets impact only one-half an inch, equaling one eighth of an inch click adjustments, and, conversely, at two hundred yards the same four click adjustments will move bullet impact two inches. Varmint and target scopes, utilized at long ranges and/or small targets, commonly have one eighth inch adjustments. Some low power scopes, utilized on rifles for large, dangerous game at close range, sometimes have half inch clicks on their adjustments. One-quarter inch adjustments are, however, the standard for the majority of telescopic sights.
Move the adjustment the direction you want the bullet to move, for example, after you initially bore site your firearm and fire it at a target at 100 yards, you find the bullet impact is three inches right of the bull and three and a half inches high. Look at one of your adjustment knobs on your scope, in this case you decide to correct elevation first. One of the adjustments is always marked, in this case an UP is marked just off the adjustment knob with a line pointed counter clockwise around the adjustment knob. However, you want to lower the bullets impact on target by three and a half inches, obviously you have to move the adjustments clockwise, the opposite of the scopes counterclockwise UP position, but how many clicks on the adjustment knob? The gun is three and a half inches high and the scope has the standard quarter inch click adjustments at one hundred yards. Four clicks equal one inch at one hundred yards, but you want three and a half inches of bullet movement, not one inch. Three inches times four quarter inch clicks plus one half inch, equaling two quarter inch clicks gives you a total of fourteen clicks down, in this case fourteen clicks clockwise. Same thing for the windage adjustment, the rifle is shooting three inches right, bullet impact has to come left, click the windage knob twelve clicks left (4 clicks per inch times 3 inches=12 clicks). These adjustments will bring the bullets impact to the center of your target; it will be right on at one hundred yards, a good sighting in range for the 30/30. Remember, however, if you change brands and/or bullet weight of ammunition you most likely will have to re-sight your rifle because of the change in the barrel harmonics.
Happy hunting.