1-nx scopes (1-4x, 1-5x, 1-6x, etc) are a natural fit for AR-15s. You get almost the close-up performance of a red dot with much better long distance performance. Aiming a red dot at distance is difficult not just because there isn’t any magnification but also because there are no reference marks for windage or elevation. Not only that but with a red dot you can’t really spot your own splash like you might be able to with a magnified optic so followup shots are also less likely to connect. Deciding on a 1-nx scope can be tricky and which one you choose really depends on your budget, priorities, and preferences. If you’re a 3-gunner who really loves clear glass, good illumination, and a huge fov, you might choose a Swarovski Z6i or Kahles K16i 1-6x. On a slimmer budget? You might choose the Vortex Razor HD Gen II 1-6x. If you’re searching for the best value for a scope with decent glass and daytime bright illumination you should check out the Burris XTR II 1-5x. But if you want a 1-nx scope for your AR-15 that has good glass, good illumination, and offers great long range performance, look no further than the Leupold Mark 6 1-6x scope with the CMR-W 5.56 reticle.
A lot has been written about the illumination on the Leupold Mk6. On a first focal plane (FFP) 1-nx scope, such as the Mk6, illumination is very important because that is what you’re relying on at 1x to draw attention to your aiming point. Reticles that are thicker near the edges can help but you really need something that stands out in the center very clearly if you want to shoot well at speed at 1x. With FFP scopes the illuminated part might be a horseshoe or circle at 6x and then becomes a small donut at 1x. If the tiny donut is bright enough it’ll be fine and that is the supposed problem of the Mk6.
The illumination on the Mk6 is definitely daytime bright but if your eye is not centered within the scope the illumination will disappear as if you turned it off. People talked about this problem before I got the scope and I honestly wasn’t sure how big of a deal it would be. I wanted a scope that had good glass and was lightweight and durable. I also wanted a scope that could be used effectively at longer distances but not at the expense of poor close-up performance. However, seeing a YouTube video of BJ Norris shooting well at the 2014 Superstition Mystery Mountain 3-Gun with a Mk6 helped alleviate my concern. It turns out, for me, that problem is overblown. The illumination does turn off on me sometimes but almost always at the higher magnification levels where you’re most likely to be using the holdovers anyways. At 1x the donut stays bright and it’s easy to shoot fast with.
The CMR-W 5.56 reticle is what really sold me on the scope and, in my opinion, what separates the Mk6 from other 1-nx scope options. It may look a little busy at first but at 1x the “Christmas tree” reticle isn’t too visible and at the highest magnification levels (remember, because it’s a FFP scope the subtensions are still accurate if it’s at 4x, 5x, 6x, or anywhere) the reticle offers a ton of features that allow it to excel at long range. A lot of scopes offer holdovers to 600 yards or so but the Mk6 has holdovers to 900m (calibrated with a 62gr bullet at 2970 fps with a 50m zero and an AR-15 sight height). A nice touch is that the reticle also has holdovers every 50 meters, such as at 650m, 700m, 750m, and so on, whereas pretty much every other 1-nx scope has holdovers only every 100 yards or meters. This really helps to be more precise with your elevation holdovers as the distance between the typical 100y/100m holdover subtensions can become quite substantial. The crucial feature though is the wind holds. The CMR-W 5.56 has wind holds for 5.56 at 5 mph, 10 mph, 15 mph, and 20 mph and are extremely useful for quickly applying precise wind corrections. Most bullet drop compensation (BDC) reticles don’t offer these wind holds so you’re generally forced to either guess a hold in space in the reticle or use target widths or some other reference to apply wind corrections, which I feel is isn’t nearly as easy or repeatable as it is with the precise holds of the Mk6.
I tested the Mk6 recently out to 843 yards on a full-sized torso steel target. The AR-15 had a factory Daniel Defense upper with a lightweight 16″ barrel and a 12″ DD Lite quad rail. The lower had a Geissele SSA trigger with a Magpul grip and CTR stock. The Leupold Mk6 was mounted in a Larue SPR mount. Hornady 75gr BTHP handloads were used and chronied at 2603 fps over a Magnetospeed V3. The gun was zeroed at 50y however and not 50m as I prefer yards. The rifle was shot with a Harris S-BRM 6-9″ bipod and Tab Gear rear bag off a bench.
I plugged in the Bryan Litz tested ballistic coefficient for the Hornady 75gr BTHP bullet into Strelok+ on my Android smartphone along with other pertinent information and popped up the reticle holdovers for my AR-15/scope/ammo setup. Even with a different load the holdovers are close. The 500m line corresponds to 472 yards and the 700m line comes out to 671 yards. To shoot at the 843 yard steel I would be holding between the 850m and 900m holdovers on the Mk6, which with our load came out to be 827 and 876 yards, respectively.
The wind was constantly over 10mph and quartering at the firing line. In the Strelok+ picture you can see that the wind holds in the reticle are pretty accurate. With 843 yards plugged into the program as the target distance, you can see that the 12 mph hash mark in the horizontal stadia (the horizontal line to the left and right of the circle/dot center aiming point that has markings of 5.9 mph, 12 mph, 18 mph, etc) corresponds almost perfectly with 12 mph in the reticle at the 843 yard holdover point if you follow the 12 mph hash mark down. I guessed a hold between 7 and 10 mph in the reticle and sent some shots down range. I only missed a few before I started connecting. We managed to capture some video of a miss followed by several hits in the YouTube video. The miss is easy to detect as it clearly impacts the ground to the right of the target. The hits though were a little more difficult as the target wasn’t swinging. The giveaway is the bullet fragments hitting the ground in front of the target.
Another key feature in the reticle is the ranging capability. You can estimate range via the width of a torso in the BDC holdovers like with most Trijicon ACOG reticles. On the BDC you can also estimate range with 12″ vertical objects. Lastly there’s both horizontal and vertical mil scales if you want to use a MilDot Master or calculator.
The glass in the scope is really nice and offers a great picture, even at longer distances. I was able to spot my own splash when I missed at the 843 yard target. I also really like the turrets as the lock prevents any accidental zero shift but still allows you to put elevation on the turrets by simply pushing down on the lock as you spin the turrets. This can be useful if you want to shoot at targets even farther than the reticle allows (876y in my case). Simply add a couple mils of elevation to the scope and put that zero offset in Strelok+, or whatever your ballistics calculator of choice is, and recalculate the reticle holds. Adding 2 mils of elevation to the Mk6 in my setup allows for a maximum of a 946 yard holdover at the 900m mark in the reticle. I know I wouldn’t be shooting well at that distance but I’m sure many others would fare better.
We’ve owned a half-dozen different 1-nx scopes now and the Leupold Mk6 is my favorite. It offers a good combination of features that appeal to me. It has daytime bright illumination, a good reticle, and is relatively lightweight. I wanted to use the scope for longer distances but still be able to shoot quickly at close targets. I felt that while something like the Leupold Mk8 1.1-8x with Horus reticle might be better for long range I don’t really like mil-based reticles (Horus or straight mil) in 1-nx scopes as I feel that BDC reticles are faster and easier to use. Plus, BDC reticles offer the quick ranging capability. Luckily for me, the Mk8 1.1-8x was out of my budget anyways. That left the Leupold Mk6 1-6x with CMR-W 5.56 reticle. It isn’t perfect but it checks the boxes the best for me. And so far, I haven’t been disappointed.