Tactical Scopes: Mechanical Performance Summary

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A great scope is more than just sharp glass. I surveyed 700+ shooters, and mechanical performance was rated as the most important feature of a scope. In fact, mechanical performance received 30% more votes than optical performance. A scope that doesn’t track, or doesn’t have repeatable adjustments seems to be viewed as the biggest flaw a scope could have.

Mechanical performance is a critically important topic, but has been largely neglected in the shooting press. Here is what Dennis Sammut, Founder/President of Horus Vision, has to say on the subject:

“Yearly, a virtual mountain of written information is spewed forth from the word processor of gun writers. … When the subject is “riflescopes,” the writer’s primary focus is on external looks, dimensions, weight, reticle, image resolution, power range, and similar physical characteristics. It is impossible to find an article that evaluates a particular riflescope or runs a test on a group of a riflescope’s ability to accurately respond to elevation and windage knob adjustments.”

That was true until now. I conducted several objective tests focused specifically on mechanical performance. This post provides the overall summary and scores for each scope related to mechanical performance, and explains what those scores are based on. Mechanical Performance Part 1 reviewed the test and results that evaluated how precisely calibrated the mechanical clicks were on each scope. Part 2 reviewed several other tests related to mechanical performance, including return to zero, reticle cant, reticle calibration, elevation adjustment range, elevation travel per revolution, windage adjustment, and the live-fire, magnum box test.

Before anyone throws a fit about this not being the “right” breakdown … remember, I’ve published the details for every single piece of data this is based on, so feel free to calculate your own score based on whatever factors you’d like. I believe this is a good general breakdown, so I wanted to accommodate the guys that just want a higher-level overview without having to read the details of every test.

Here is a breakdown of what all played into the overall mechanical performance score:

Overall Mechanical Performance Score

• 50% Precisely Calibrated Clicks – This score indicates how well the advertised click adjustments matched the actual measured adjustment. For example, when you dial for 10.0 mils of adjustment, does that equate to exactly 10.0 mils … or is it 9.9 mils or 10.1 mils? Most turrets don’t track perfectly, even on these high-end scopes. In fact, I only found 4 of these scopes that tracked perfectly all the way to 20 mils of adjustment. I provide a detailed breakdown of how this element was calculated later in this post.
• 25% Return To Zero – This indicates the scopes ability to repeatedly return to zero through multiple elevation adjustments. All scopes in this test were able to do this perfectly. However, I’m trying to establish a benchmark scoring system, because I may test mid-priced scopes in the future. This is an important element that not all scopes will be able to handle as well as these did, so I wanted to keep it as part of the mechanical score, even though all of these scopes received full credit. (Read how I tested this)
• 15% Max Elevation Adjustment Range – This is also referred to as a scope’s “Internal Adjustment Range” or “Overall Elevation Travel.” It’s simply the maximum amount of much elevation adjustment the scope allows. I measured this directly. For long-range shooters, more is better. It’s frustrating to be limited by the travel built into your scope. For this score, a scope with 40 mils of adjustment or more received full credit, because that should be more than enough for 99.9% of shooters out there (it is enough adjustment for a 338 Lapua to reach beyond 2500 yards). A scope with 10 mils or adjustment or less received no credit. (Read how I measured this)
  
• 10% Reticle Cant – Some of these scopes had a measurable amount of cant in their reticle, which is when the crosshairs don’t perfectly align with the directions of the elevation and windage adjustments. I explain this more in Part 2, and include diagrams to help you visualize what I mean. In that post, I also look at what that means to your trajectory at long range, and that’s how I landed on the scoring where 2% or more reticle cant was unacceptable and the scope would receive no credit at that point. Obviously, if there was no measurable cant, the scope received full credit. (Read how I measured this)
  

So without further ado, here are the results for the overall mechanical performance score, weighted as described above:

I realize these results may not align with popular opinion within the shooting community, but I’d highly encourage you to go read how I conducted the tests and collected the data before you dismiss this. And, it may be fitting to repeat the disclaimer that I’m not affiliated with or sponsored by any of these manufacturers. Although a few have offered to pay to sponsor this website, I’ve declined every offer to date so that I can remain independent and don’t have to feel like I have to pull punches if I discover flaws in their products. I’ve definitely put a ton of effort into evaluating and presenting this information the most honest and unbiased way possible.

While several scopes performed very well, only 4 scopes were PERFECTLY calibrated all the way through 20 mils of adjustment:

• Hensoldt ZF 3.5-26×56
• Kahles K 6-24×56
• US Optics ER25 5-25×58
• Valdada IOR RECON Tactical 4-28×50

Since that was such a big part of the score, you can see that all of those scopes ended up towards the top of the list. The Nightforce ATACR 5-25×56 and Nightforce BEAST 5-25×56 were also notable finishers in terms of mechanical performance, and their extremely generous elevation travel allowed them to end up among the other 4 scopes I itemized above. The Leupold Mark 6 3-18×44 and Leupold Mark 8 3.5-25×56 scopes also performed very well, with both finishing in the top half.

You might notice that the Leupold Mark 6, and Nightforce ATACR both have “2nd scope” by their label, and the March Tactical 3-24×42 FFP scope has “Average of 2 scopes.” The first time I ran through the mechanical tests, those 3 test scopes showed more error than others in the test. I thought the results might be a result of a defective unit, so I contacted each manufacturer. First, I completely understand that it is impossible (and impractical) for every scope to be perfect, so I always want to give a manufacturer a chance to fix something like that before I publish results that may not be representative of the typical unit. At the same time, I’m committed to being completely transparent and honest with my readers. So if I run into something like this, I give the manufacturer a shot at fixing it, and then in the article I mention the issues I ran into and how it worked out in the end. That seems like the most respectful and fair approach for both the manufacturers and readers.

So Leupold, March, and Nightforce were all kind enough to send me another test scope (I didn’t have time to wait on the units I had to be repaired, since this project was already running behind schedule). When I retested the new Leupold Mark 6 and the Nightforce ATACR scopes, they both performed considerably better than the original scopes. The first Leupold Mark 6 had an average of 3.7% of error in the elevation adjustment through 20 mils, while the replacement performed stunningly with an average of just 0.1% of error. The Nightforce ATACR followed suit with the original coming in with an average of 1.8% of error in the elevation adjustment through 20 mils, and the replacement coming in with 0.4% of error. In both of those cases, I feel like it was an issue with the particular scope and the original results were not indicative of what you can reasonably expect from Leupold or Nightforce. Either of those companies would quickly repair any scopes that performed like the original set of scopes I tested. So in both cases, I’ve only included how the second scope performed in the charts and scoring.

However, the replacement March scope that Kelbly.com sent unfortunately didn’t follow that same pattern. While the 2nd March scope performed similar to the original, it was actually slightly worse overall. The original scope had an average of 2.2% of error in the elevation adjustment through 20 mils, and the replacement had an average of 2.7% of error. I really didn’t know exactly what to do with those results, because with similar results this didn’t seem to simply be due to a defective unit like the Leupold and Nightforce scopes. I decided the best approach was to simply average the results from both scopes and publish that as my results for the March scope.

Scoring for Precisely Calibrated Clicks

I went into exhaustive detail regarding how I performed these tests, and the data I collected in Part 1 of the mechanical performance, so I won’t repeat that info here. I essentially tested how well the elevation turret adjustment aligned with what was advertised and indexed on the scope. I used Horus calibration targets and Spuhr scope mounts, and was extremely careful about how I performed the tests. Here is a quick image that shows the basic setup, but please check out Part 1 for more details.

I checked each scope at 4 different adjustments: 5 mils, 10 mils, 15 mils, and 20 mils. Most of the scopes used mils, but a few used MOA adjustments, and the Zeiss scope actually used Shooter’s MOA (which is slightly different). I also tested those scopes at 4 similar adjustment intervals.

Although testing up to 20 mils of adjustment may seem extreme, any error in the turret typically has a compounding effect, so even a small amount of error becomes measurable at that extreme adjustment. But for the scoring, I weighted error found at 5 mils the heaviest, with decreasing weight for each increment up to 20 mils. I did this because most shooters live in those lower adjustments, so they’re weighted more heavily. The 5 mil adjustment represents 40% of the score, 10 mil adjustment is 30%, 15 mil adjustment is 20%, and the 20 mil adjustment is 10% of the score.

Then, I had to decide how much a certain amount of error should penalize the score. In Part 1, I walked through a few examples that showed how much 1-2% error equates to at long-range. I decided 3% of error would make it very tough to account for and get shots on target, so if 3% of error or more was found the scope would not receive credit for that adjustment. If the scope was dead on (i.e. 5.0 mils of adjustment on the scope equates to exactly 5.0 mils of adjustment at 100 yards), then it received full credit.

So here is the scores for Precisely Calibrated Clicks, according to the weights and scoring technique outlined above. For more details or to see the underlying data, check out Mechanical Performance Part 1.

*The Zeiss Victory Diavari 6-24×56 scope actually didn’t have enough elevation travel to get to the 4^th adjustment (72” at 100 yards), so it didn’t receive credit for that one (but that only makes up 10% of the overall score). The Zeiss Victory scope was the only scope in this class that didn’t provide at least that much adjustment. The average among the other scopes was 30 mils, but the Zeiss had the equivalent of 16 mils. See Part 2 for a direct, visual comparison of all the scope’s elevation travel.

You can clearly see the 4 scopes that were perfect through all four adjustments at the top of the chart. 12 scopes were dead on at 5 mils, and 7 were dead on at 10 mils. I measured this down to 1/2 click granularity.

Many shooters don’t need to adjust beyond 10 mils, because that is enough adjustment to take most modern cartridges to 1,000 yards. Here is a little larger list with scopes that performed perfectly up to at least 10 mils:

• Hensoldt ZF 3.5-26×56
• Kahles K 6-24×56
• Leupold Mark 6 3-18×44
• Leupold Mark 8 3.5-25×56
• Nightforce ATACR 5-25×56
• US Optics ER25 5-25×58
• Valdada IOR RECON Tactical 4-28×50

And here are few scopes that were very close to perfect up to 10 mils. The scopes below weren’t off by more than a 1/2 click at either 5 mils or 10 mil adjustments, which is still great performance and more than adequate for most shooters:

• Bushnell Elite Tactical 3.5-21×50
• Nightforce BEAST 5-25×56
• Nightforce NXS 5.5-22×50
• Schmidt and Bender PMII 5-25×56
• Valdada IOR 3.5-18×50
• Steiner Military 5-25×56

Other Post in this Series

This is just one of a whole series of posts related to this high-end tactical scope field test. Here are links to the others:

1. Field Test Overview & Rifle Scope Line-Up Overview of how I came up with the tests, what scopes were included, and where each scope came from.
2. Optical Performance Results
   • Summary & Part 1: Provides summary and overall score for optical performance. Explain optical clarity was measured (i.e. image quality), and provides detailed results for those tests.
   • Part 2: Covers detailed results for measured field of view, max magnification, and zoom ratio.
3. Ergonomics & Experience Behind the Scope
   • Part 1: Side-by-side comparisons on topics like weight, size, eye relief, and how easy turrets are to use and read
   • Part 2 & Part 3: Goes through each scope highlighting the unique features, provides a demo video from the shooter’s perspective, and includes a photo gallery with shots from every angle.
   • Summary: Provides overall scores related to ergonomics and explains what those are based on.
4. Advanced Features
   • Reticles: See every tactical reticle offered on each scope.
   • Misc Features: Covers features like illumination, focal plane, zero stop, locking turrets, MTC, mil-spec anodozing, one-piece tubes
   • Warranty & Where They’re Made: Shows where each scope is made, and covers the details of the warranty terms and where the work is performed.
   • Summary: Overall scores related to advanced features and how those were calculated.
5. Mechanical Performance
   • Part 1: Shows how precisely calibrated the clicks are on each scope.
   • Part 2: Reticle cant, measured elevation travel for each scope, and other mechanical tests
   • Summary: Overall scores related to mechanical performance.
6. Summary & Overall Scores: Provides summary and overall score for entire field test.