TECH Tip: How to Verify Your Scope’s True Click Values
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.
Similar Posts:
- How to Check Your Scopes’ True Click Values
- Check Your Scope's Click Value–You May Be Surprised
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- How to Verify Your Scope’s True Click Values — Box Test
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Tags: Box Test, Click Test, Elevation, Mil, MOA, Optics, Scope, Test, Turret
Always a good idea to box the scope
Tend to find this is an exercise in futility for internet heroes seeking clickbait. There are far too many variables in this approach; changing heat during the test, vibration, material used for the platform, etc etc.
An industrial collimator is the only machine that gives accurate and repeatable readings.
Best way to learn your scope is to get out and shoot with it.
I agree with Richard. There are so many variables that affect shot precision. Trust the reputation of a good quality scope and then get out and shoot it under all conditions. My experience has been that the scope is right more often than me!
Editor: If you have never done a box test from a good benchrest set up you should. Bryan Litz also advocated this procedure. You may be surpised with what you find. If nothing else it can give you confidence in the optic — and you may also be able to confirm a problem when something has gone wrong. I have had two major brand scopes go bad, with inexplicable vertical shifts. The problems appeared in a match and were later confirmed with vertical click tests.
@ The Editor.
We are at an interesting point in human history and optical equipment where manufacturing techniques are such that the easy explanation of “scope failure” that we could use up to the first years of the 21st century no longer apply.
A well made scope from a number of named manufacturers are precision pieces. What they do show, more often than not, is an error in reloading, technique, set up that the shooter is not prepared to accept and therefore the scope is broken.
By all means do a box test if it makes you feel happy. But buy the best scope you can afford and concentrate more on reloading and shooting technique.
Richard: I think it’s incorrect to suggest that the latest generation scopes won’t fail. I have seen premium scopes from various makers “go south” or, not work to spec when new. I have seen a National record holder replace a $2800 scope in the middle of the Nationals because it failed.
With an accurate rifle a box text DOES reveal important facts. If you have a 2 MOA rifle, or are shooting from a wobbly rest, different story. But things do break or fail. Specific Example. My own “L-brand” 8-25X LRT. At a 600-yard match, we zeroed on steel, confirmed with sighters. Then went for record and put 3 shots inside two inches on paper. The final two shots went straight down to 6 o-clock, 18″ below the group. Vertical test performed after match showed erratic vertical of Multiple MOA. Scope shipped to Oregon. Returned 1 month later with a list of 15+ internal parts that were replaced by the manufacturer due to “internal components failure”.
But box testing is not just to confirm breakages. For long-range shooting it is vital to determine if your “1/4 MOA click” is actual 1.047″ at 100 yards/4 or something else. Some scope are closer to 1.000″. A click-by-click test can also reveal lash issues that also still affects some modern scopes.
Anyone denying that even the best/most expensive brands of scope don’t leave the factory with something other than the stated click value is living in a state of denial. Pure and simple. Even if the scope tracks perfectly for the first 20 moa, there is no guaranty that the next 10 will too. I am in the trust but verify camp. Would I send a 1/4 moa scope back that tracked perfectly, but at 1/4″. No. but at least I know how to adjust for the discrepancy. In the day of ethical 600+ yard shots on game, it would be unethical not to confirm what your scope really does. I have had to send Mark 4 Leupolds back because they didn’t track, and have friends that had to send Nightforce’s back. It happens. Thankfully not often, though.
A big factor also is the scopes manufacturers. Cheap glass aren’t reliable in adjustment increments. Stick with Leopold, Nightforce, Schmidt and Bender, Vortex, Sig Sauer and US Optics and Bushnell and Burris and EOTech. I’ve found over the years that you get what you pay for. Also depends on caliber and projectile weight. Using the 7.62×51 with 168gr out of a 20” tube is pretty much dead on with good glass in my experiences. My 6.5C is also really close also. Not enough deviation to effect combat or target accuracy. Semper Fi and lets stay a country of riflemen.
There is guessing/assuming, and there is knowing. One method worth considering is to build a bench scope mount so that the scope cannot move as adjustments are made, and to use piece of graph paper for a target at a carefully measured distance, close enough to see the details, and far enough for the scope to be focused , to check tracking. In the benchrest game the issue of holding a point of aim from shot to shot has been an issue, and relatively affordable means of testing are available.
That .047 of a inch might and only might be noticeable in that famed Houston Texas warehouse and with one of their better benchrest guns.
Care to calculate what 47 thou at 100 yds turns into at 1000 yds with a 308? It matters more than you think! 4.7% error on 337 inch drop means you’re off 16 inches!
The sighting variation of 0.047 inch at 100 yards becomes 0.47 inch at 1000 yards. One thousand yards is 10 times 100 yards so the error is multiplied by 10. The 337 inch drop you reference is caused by acceleration due to gravity. This does not change due to sighting error.