Say you have a new scope and the specs indicate that it is calibrated in quarter-MOA increments. You know that one MOA is equal to 1.047″ inches at 100 yards. So you think four clicks will move your point of impact. Unfortunately, you could be wrong. You shouldn’t always rely on the manufacturer. Due to the production tolerances, you should test your scope in order to determine how much movement is actually delivered with each click of turret. It could move a quarter MOA, a quarter inch, or something else. (Similarly, scopes that advertise 1/8-MOA clickings may deliver more than 1 MOA for eight clicks.
Lindy, a reader, explains how to check the clicks. “First of all, make sure that the rifle is unloaded. Use a 40” or larger carpenter’s rule and mark a visible mark (such the center of an orange Shoot’N’C Dot) at 37.7″. On mine, I placed 2 dots side by side at every 5 inches so I could count the dots quickly. Mount the ruler vertically with zero at the top, and carefully measure 100 yards.
Place the rifle on sandbags, or another rest. With the rifle’s hundred-yard zero, use maximum magnification to aim the center crosshairs carefully at the top of your ruler (zero-end-point). Assist the assistant to turn the knob on 36 (indicated MOA) (i.e. Be careful not to move your rifle when you click 144 times. You will need help, as it is difficult to keep the gun still if you turn the knobs by yourself. Each click will move the reticle a little bit toward the bottom. When your assistant is finished clicking, note where the crosshairs are located in the center. If the scope has been calibrated correctly, it should be at that 37.7-inch mark. If not, note where 144 clicks places you on the ruler to determine your actual click value. Repeat this as many times as you need to in order to get a repeatable, “rock-solid” value. You know now, for that scope how much each click moves the reticle when you are at 100 yards. This will scale proportionally to longer distances. This optical method is superior to shooting because it eliminates the uncertainty associated with determining group center.
Using this method, i discovered that my Leupold 6.5-20X50M1 had click values calibrated in what i called ‘Shooter MOA’ rather than true MOA. This means that 4 clicks moved the POI 1.000″‘ instead of 1.047″‘ (true MoA). This is about a 5% mistake.
I’ve tested a lot of scopes and found that many have click values that are significantly different from what the manufacturer advertised. You can’t rely solely on printed specifications, as each scope is unique. You can’t tell how much your scope moves until you test it.
I’ve found that the true click value can vary not only by manufacturer but also by model and unit. My Leupold M3LR 3.5-10 was perfect. My U.S.O. was also dead on. SN-3 with H25 reticle. But other SN-3s are off, as is my Leupold 6.5-20X50M1. “My policy is to check them all.”
From the Expert: “…Very important article, particularly from a ballistics perspective. If, for example, a ballistics software predicts a 30 MOA drop at 1000 yards, but you dial in 30 MOA to your scope and hit either high or low, then it’s easy to start questioning BCs, MOAs, and other things. In my experience, I’ve found that more than half of the time error for trajectory prediction at a long range is due to scope adjustment error. The test described in this piece is a must for serious long-range shooting.” — Bryan Litz of Applied Ballistics LLC.
Bryan uses a Tall Target Test as well to determine the true click values. CLICK HERE to view a detailed article explaining Litz’s Tall Target Test.
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