Verifying the True Value of Your Scope Clicks
Let’s say you’ve purchased a new scope, and the spec-sheet indicates it is calibrated for quarter-MOA clicks. One MOA is 1.047″ inches at 100 yards, so you figure that’s how far your point of impact (POI) will move with four clicks. Well, unfortunately, you may be wrong. You can’t necessarily rely on what the manufacturer says. Production tolerances being what they are, you should test your scope to determine how much movement it actually delivers with each click of the turret. It may move a quarter-MOA, or maybe a quarter-inch, or maybe something else entirely. (Likewise scopes advertised as having 1/8-MOA clicks may deliver more or less than 1 actual MOA for 8 clicks.)
Reader Lindy explains how to check your clicks: “First, make sure the rifle is not loaded. Take a 40″ or longer carpenter’s ruler, and put a very visible mark (such as the center of an orange Shoot’N’C dot), at 37.7 inches. (On mine, I placed two dots side by side every 5 inches, so I could quickly count the dots.) Mount the ruler vertically (zero at top) exactly 100 yards away, carefully measured.
Place the rifle in a good hold on sandbags or other rest. With your hundred-yard zero on the rifle, using max magnification, carefully aim your center crosshairs at the top of the ruler (zero end-point). Have an assistant crank on 36 (indicated) MOA (i.e. 144 clicks), being careful not to move the rifle. (You really do need a helper, it’s very difficult to keep the rifle motionless if you crank the knobs yourself.) With each click, the reticle will move a bit down toward the bottom of the ruler. Note where the center crosshairs rest when your helper is done clicking. If the scope is accurately calibrated, it should be right at that 37.7 inch mark. If not, record where 144 clicks puts you on the ruler, to figure out what your actual click value is. (Repeat this several times as necessary, to get a “rock-solid”, repeatable value.) You now know, for that scope, how much each click actually moves the reticle at 100 yards–and, of course, that will scale proportionally at longer distances. This optical method is better than shooting, because you don’t have the uncertainly associated with determining a group center.
Using this method, I discovered that my Leupold 6.5-20X50 M1 has click values that are calibrated in what I called ‘Shooter’s MOA’, rather than true MOA. That is to say, 4 clicks moved POI 1.000″, rather than 1.047″ (true MOA). That’s about a 5% error.
I’ve tested bunches of scopes, and lots have click values which are significantly off what the manufacturer has advertised. You can’t rely on printed specifications–each scope is different. Until you check your particular scope, you can’t be sure how much it really moves with each click.
I’ve found the true click value varies not only by manufacturer, but by model and individual unit. My Leupold 3.5-10 M3LR was dead on. So was my U.S.O. SN-3 with an H25 reticle, but other SN-3s have been off, and so is my Leupold 6.5-20X50M1. So, check ‘em all, is my policy.”
From the Expert: “…Very good and important article, especially from a ballistics point of view. If a ballistics program predicts 30 MOA of drop at 1000 yards for example, and you dial 30 MOA on your scope and hit high or low, it’s easy to begin questioning BCs, MVs, and everything else under the sun. In my experience, more than 50% of the time error in trajectory prediction at long range is actually scope adjustment error. For serious long range shooting, the test described in this article is a MUST!” — Bryan Litz, Applied Ballistics for Long-Range Shooting.
the H25 reticle is in mils…
is the test different?
Very good and important article, especially from a ballistics point of view. If a ballistics program predicts 30 MOA of drop at 1000 yards for example, and you dial 30 MOA on your scope and hit high or low, it’s easy to begin questioning BC’s, MV’s, and everything else under the sun. In my experience, more than 50% of the time error in trajectory prediction at long range is actually scope adjustment error. For serious long range shooting, the test described in this article is a MUST!
Very interesting, but you must make sure that your barrel is at 100 yards, couse few centimeters more or less than 100 yards can make different data.
Gary Meyer: One mil equals 3.6 inches at 100 yards, so 10 mils (worth of clicks) at 100 yards should be 36 inches. Using these figures you should be able to determine check the accuracy of a scope having mil adjustments, rather than MOA adjustments.
I don’t want to sound picky, but an engineer’s tape would give you a true 37.7 inch measure. I don’t know of any “carpenter’s rule” that is in tenths or hundredths of an inch.
This is nice for MOA adjustments then you have Mil dot variations from NATO milradian(1 NATO MRAD = 3.375″ @100 Y) to Russian milRadians (1 Russian MRAD = 3.6″ @100 Y) and Swedish Milradians (1 Swedish MRAD = 3.428″ @100)
Why does this have to so convoluted and shitty.
The real question is why do scope makers either not know what their scopes adjust at, or why are they lying to everyone?
I suspect most(even high end) makers generalize MOA as ROUGHLY 1 IPHY.
Most Leupolds adjust in IPHY, but their Mk4s are true MOA. A Nightforce NXS I tested produced 1.09 IPHY per ‘MOA’ of adjustment, and this validated other reported results.
Your ballistic software needs to allow input for actual adjustment value per click. Mine does & with this I use ‘click cards’ in the field which define adjustments in clicks rather than MOA.
It’s been suggested that MOA is easier than clicks to lookup & set in the field, but no it is not, -especially when your scope doesn’t actually adjust in true MOA.
Other elements that need to be taken into account once ranges exceed approximately 300 meters include wind direction, air pressure and density, humidity, temperature and elevation. For very long range shooting, over 1,000 meters the Coriolis effect also must be considered in some instance. Cartridge and projectile performance data must also be included. Whatever the perceived strengths and weaknesses that scope adjustments indicate (there is a very strong case for adoption of industry universal standards regarding scope adjustments and repeat ability), it is advisable to tailor a range card based on the adjustment parameters of the scope being used and the performance characteristics of the cartridge in use at the time. If adjustment repeat ability of a particular brand of scope is assured through observation, that is what one needs to work with for consistent performance. The discussion on scope manufacturer dialing standards has been going on for decades and still has not been satisfactorily addressed in general, especially at the lower price range of scopes. A computer calculation of a trajectory, as helpful as it, is only a model of an ideal simulation. In a real world scenario, slight adjustments will always need to be made – very carefully. Hence the need for a range card tailored for the one scope and load data in use at the time.