Like barrels, triggers, and all the other choices, Ar-15 optics are a challenging one. There’s a lot of misunderstanding and “fluff” out there. I want to take a few moments and discuss some thoughts on optics selection.
There are already some really great guides out there, but they focus more on particular classes of optics. Those guides dig a bit more specifically into particular classes of optics. This post is more like a broad overview of how to think about each class and what you would use it for. I’ll throw some of my personal favorites in there for good measure.
As a refresher, I have two fundamental rules for buying any firearms-related gear:
- Let the mission dictate the configuration
- Buy nice or buy twice
If you haven’t read my guide for buying your first AR-15, where I introduced these rules, I’ll recap it for you.
The actual purpose your weapon fulfills drives the choices you make. Too many people buy something first, because the internet told them to, and then try and shoehorn it into a role it was never designed for. AR-15 optics are a bit like the rifles themselves: if you don’t have a particular role in mind, then the best path is typically a “general” option that does most things reasonably well.
On the second point, I’m not telling you to spend stupid amounts of money on something. I’m simply saying buy something nice enough that it will last a long time and serve you well. It doesn’t have to be “best in class.” Just buy quality.
The Five Classes of Rifle Optics
In 2008, Zak Smith wrote an article for Shotgun News detailing his thoughts on fighting optics. He categorized optics into three basic types: CQB, DMR, and SPR. Each type is best suited for different engagement ranges and weapon employment method.
I liked his general breakdown. However, a lot has changed in the world rifle optics since 2008. We need to adjust how we approach things
I divide rifle optics into five groups:
- Class I: Iron Sight Replacements
- Class II: Low Powered Fixed Magnification
- Class III: Low Power Variable Magnification
- Class IV: Mid to High Magnification
- Class V: Digital Hybrid
I derived these categories by using Zak Smith’s typography as well as the US Army’s phased plan of optics evolution. If you’ve never seen it, the Army had a presentation in 2015 where they detailed the future of military optics.
According to this slide, the Army considers my Class 1 and 2 optics to be the first generation of combat optics. Class 3 and 4 fall into the second generation group, and Class 5 aligns with 3rd generation.
Most shooters are reasonably familiar with my first four classes. The fifth is far less common. To be honest, I don’t think anyone has a very good idea of what this group is supposed to look like. However, a good example might be the Tracking Point system that’s been sitting in limbo for years. Imagine an optic using digital displays along with a computer that fires the rifle for you when the sights are properly aligned.
Class I Optics
This is the most popular type of AR-15 optic on the market. When you think of a Class I optic, you should be thinking of a Red Dot Sight (RDS).
Characteristics of Class I optics include zero magnification, parallax-resistance (not necessarily parallax-free), and a priority placed on a speedy sight picture. The increased speed comes from removing the need to align the front and rear sights with the shooter’s eyeball. Instead, you keep both eyes open and focuses on the target. The optic projects a dot onto the same visual plane.
This class of really optic rose to prominence during the early 2000s in Iraq. The intense CQB/urban operations it entailed were ideal for red dot sights. These optics are fantastic for use against moving targets or any situation where the speedy acquisition of a sight picture is the top priority.
I think of Class I optics as better versions of the M16A1 iron sights.
Use holdovers as necessary for anything outside of that point blank zero range. This class of AR-15 optics excels from bad breath distance out to 250-ish meters. They are lightweight, compact, and some can be left on for years before the battery needs to be changed. Some models do not have batteries at
If you regularly shoot from unconventional positions where a proper cheek weld is difficult or unlikely, then these optics are king of the hill. It’s also the only type of optic that will co-witness with iron sights. If you’re not familiar with the term, that means you can use your iron sights through the optic. If the dot ever fails, you can still seamlessly use your backup sights.
Class I Limitations
While Class I optics are a great choice for a general use defensive weapon, they do have limitations.
Shooters with uncorrected astigmatism may see imprecise blobs or clusters rather than nice crisp red dots. I fall into this group, as I have slight astigmatism and don’t usually shoot wearing corrective lenses. I find that battery-powered illumination is slightly worse than fiber optic.
The lack of magnification in a Class I optic also means it’s not ideal for observation and identification. It’s little help for differentiating among targets or identifying a target in relation to its background. Furthermore, Class I optics are not designed for easy zero adjustments in the field. It’s all Kentucky Windage, all the time.
Most people, in most realistic defensive situations, are well-served by a Class I type optic. They excel from 0 to 250 yards, provided your eyesight is up for the task. This is the range envelope the 5.56 is designed for, and the one where most uses of rifles occur.
Class II: Low Powered Fixed Magnification
In this category, you’re looking at rifle scopes like the famous ACOG.
This class of optic really gained traction during the US Army’s Advanced Combat Rifle trials in the 1980s. Notably, Trijicon teamed with AAI to submit an early version of the TA01 ACOG on their rifle entry. ELCAN presented an early version of the C79 with Colt’s submission. While the replacement rifle never came to fruition, the optics did.
Class II AR-15 optics flourished over the years as militaries recognized the value of ruggedized magnified optics for general military use. They are typically compact, relatively lightweight, rugged enough to put up with the abuse infantry life, and offer huge marksmanship benefits over iron sights.
The reticles in these optics usually have some form of rangefinding stadia and a calibrated bullet drop compensator (BDC). These are intended as field-expedient methods of estimating where hits will land and not intended for true precision shooting.
The BDC reticles are usually calibrated to a specific bullet moving at a specific velocity under specific environmental conditions. Deviating from these standards means that the BDC will not be correct, but should still be “close enough.” If not using a reticle with a calibrated BDC, this type of optic still works well with a point blank zero or with a Swiss Sniping 4th Generation technique.
I would venture to say that Class II optics embody the skillset of the last generation of riflemen. At least before the focus turned to vehicle-borne operations and CQB.
Class II optics truly reward proper execution of marksmanship skills, and they excel in combat environments infantry units typically found themselves in. These are not CQB optics. The use of a Class II type optic assumes that the shooter has time to see a target, move to appropriate cover, identify the target as a threat, and then apply marksmanship fundamentals to eliminate that threat.
When I did the MVT course in the mountains of West Virginia, both my ELCAN and ACOG were outstanding tools for locating and engaging hard to see targets in the wooded environment. More often than not, it seemed like those of us with magnified optics were calling out targets for the guys equipped with the Red Dot Sights.
You can use some examples of Class II AR-15 optics like you would red dot sights, but it’s not perfect. Trijicon touts what they call the “Bindon Aiming Concept” for this. The belief is that a bright enough reticle still draws the eye. So if you use a magnified optic with both eyes open and use the non-sighting eye for scanning, the brain superimposes the bright reticle over your field of view, working
This harkens back to the original Armson Occluded Eye Gunsight (OEG) and Single Point Sight used on the Son Tay Raid. In fact, Trijicon used to be called Armson USA, and was the sole importer of the Armson OEG.
A pro-tip for this type of aiming with an ACOG is to close the lens cap, if you have one, for CQB. It’s a far less distracting experience.
Like all magnified optics, Class II optics are limited by the physics of bending light through lenses. That means that the shooter must have a consistent cheek weld to account for eye relief, parallax, and the exit pupil of the optic. Incorrect alignment results in poor sight pictures and missed shots.
Magnified optics are slower to move from target to target than Class I types since the eye has to readjust and refocus as targets come into view. Class II optics, like Class I, do not usually allow for easy zero adjustments in the field for “dialing” shots. They are meant to be zeroed and left alone.
Again, it’s all holdovers, all the time. But at least Class II optics usually provide you with more reference points for those holdovers.
Lastly, Class II optics are typically fixed at a certain parallax setting and do not have diopter adjustments to account for different people’s eyes.
I mentioned the OEG style aiming system in the employment section, but it has limitations. When using a Class II optic like that, your zero is affected by
When it comes to AR-15 optics, Class II types are best suited for practical marksmanship and general dismounted shooting, where a balance must be struck between speed and accuracy at a variety of distances. They excel between 50 and 500 meters, assuming your vision is up to the task.
Class III Optics: Low Power Variable
This class of AR-15 optics is fairly new, but taking over the market.
They bridge the differences between Class I and Class II optic, adopting several characteristics of each. They usually have some way to switch between 1x , i.e. “No magnification,” and some number greater than that. When they first hit the scene, the standard was 1-4x, as with my Trijicon TR24. But as the competition picked up, so has the magnification.
It’s common to find this Class III optics with 1-4x, 1-6x, and even 1-8x options.
Most of these optics adjust magnification by rotating a lever or knob. This allows you to choose a magnification setting anywhere along the range. Another method uses a rotating prism and cam system that switches only between 1x and the other end, with no options in between. This is the system employed by the ELCAN SpecterDR.
You might have noticed that I mentioned “No magnification” when these optics work at 1x. Even though the image appears to not be magnified, the light is still passing through lenses and bending along the way. You still have to deal with the limitations that come with bending light, particularly eye relief, exit pupil, and parallax.
Eye relief and exit pupil are pretty generous, but they still don’t work as a Class I optic. Also, you cannot
The Class III group offers a fantastic range of capabilities.
Set at 1x, they are nearly as fast and user-friendly as Class I optics. Set at higher magnifications, they retain much of the same capability as Class II optics.
I used to shoot several local 3-Gun matches with my trusty Trijicon TR-24G. Being able to use the big glowing green triangle up close at 1x and then quickly switching to 4x for 200-300 yard shots gave me a huge advantage.
Class III optics have a variety of reticle patterns and illumination methods. Some have similar BDCs to Class II optics, while others employ MRAD and MOA reticles of Class IV optics.
Some illuminate the entire reticle, others only illuminate certain segments that best draw the eye in CQB situations.
The turrets on Class III optics may or may not be quickly adjustable. It really depends on the design of the scope and whether it errs more towards speed or precision. These optics usually have a diopter adjustment for eyes, and may or may not have a parallax knob, AKA a focus knob.
To an outside observer, they really offer the best of both worlds. This is why they have taken the AR-15 world by storm lately.
But there are tradeoffs.
Class III AR-15 optics are heavier than either Class I or Class II options. They usually weigh between 1 and 2 lbs without a mount. In comparison, an Aimpoint PRO weighs 11.6 oz including the mount. A Trijicon MRO comes it at a scant 4.1 oz without a mount. Stepping up to Class II, a TA-31 ACOG weighs 13.8 oz with mount, and the compact TA-33 weighs 11.7 oz with a
The Class III group also has increased mechanical complexity. That translates to a higher risk of parts breakage. Overcoming the durability issue means increased cost in engineering, manufacturing, and parts.
For example, Trijicon’s VCOG, a Class III optic designed to be as tough as their ACOG line, costs around $2500. The ELCAN SpecterDR, which switches between 1x and 4x, is around $2200. If you don’t mind losing the ruggedness aspect of the high-end options, other quality Class III optics cost between $600 and $1500.
Class III optics occupy a solid middle ground where they are the jack of all trades, but master of none. They make ideal optics for Recce rifles.
They are can be nearly as fast as Class I optics up close, but lose out due to eye relief and parallax. They can be as useful at distance as Class II
If you do not need to operate on the extremes of speed and/or durability, then the Class III is probably a good option for you.
Class IV Optics: Mid to High Magnification
This is analogous to Zak Smith’s Type III optic for SPRs. I look at this category as optics geared more towards precision AR-15 optics t
For the most part, Class IV optics have all the same traits as Class III, with a few notable changes. The low-end magnification in this class is greater than 1x, and will usually be 2.5, 3, or 4x. The high end will probably be somewhere between 9x and 16x, or beyond.
The reticles will almost always be of MRAD or MOA design, and the turrets should are readily adjustable to dial for range and windage.
These optics effectively take the rifle to the limits of its capability.
The higher magnification levels of Class IV optics are useful for observation and target identification, but can severely limit how a rifle is used. More magnification means more movement in the scope. Things that you might not otherwise
For this reason, Class IV optics are mostly limited to supported positions where you can mitigate these instabilities.
I only advise Class IV optics for AR-15 rifles that will primarily be used from a bench or other stable platform in a long-range or precision shooting format. For practical marksmanship or field use, most shooters will be better served by an optic from Class I, II, or III.
Class V Optics: Digital Hybrids
Class V represents the future.
The optics in this group use a mixture of optics, computers, and displays to revolutionize how you aim. It’s the stuff of science fiction.
I’m not talking about night vision or thermal sights that overlay a reticle, but rather actual computers that provide real-time information to the shooter and/or calculate ballistics on the fly.
I attribute the creation of this class to the Tracking Point system introduced several years back. The company struggled mightily since its introduction, but I predicted back then that the technology would get smaller and cheaper over time. This optic integrates laser rangefinding, ballistic computer, digital display, and even includes a fire control system to automatically fire the rifle when aligned to the correct point of aim.
I don’t particularly care for the last bit, but it exists. The shooter isn’t looking through glass with the Tracking Point scope, but a digital picture zoomed in like a video camera. Something to remember with this optic is that if the electronics fail, the whole scope is dead, you cant see through it.
That last bit is the important part. If you look at the Army’s slide up at the beginning of the post, they explicitly stated that the optic must still be usable if the electronics fail.
In 2014, Trijicon paired up with Kopin to produce an optical overlay system tailored to this need. To my knowledge, the project still hasn’t won any contracts, but the prototypes are out there.
Whenever this technology is ready for the prime time, you can bet that the paradigm will shift for everything.
Combining AR-15 Optics Groups
I skipped over this point while writing. You always have the option of combining classes of optics together on the same weapon system.
An obvious example is mounting miniature red dot sights, like the Trijicon RMR, on top of Class II optics like the ACOG. Another is using flip-to-side magnifiers (Class II) in front of red dot sights (Class I). Yet another is mounting offset miniature red dots (Class I) next to Class IV rifle scopes.
Another interesting combination is Leupold’s D-EVO system. This uses a prism system to place a red dot picture and magnified sight picture directly in front of your eye. You don’t have to change your cheek weld at all to choose between the two.
These combinations certainly work fine if you don’t mind the increased weight and cost. But there are some other downsides you should be aware of.
Combining two different optic types on the same rifle helps each one mitigate the faults of the other. But you have to give something up in return, and this usually shows up as ergonomics.
For example, mounting a miniature red dot on top of a Class II optic means you will sacrifice a solid cheek weld to use it. That may not be a big deal at close ranges, but it’s not how the optics are designed to be used.
Another common solution is using offset optics tilted at 45 degrees or so from the main optic. This keeps the backup sight closer to the bore of the rifle, and saves your cheek weld, but you also limit yourself to only using it on one side. Even more so, that offset-mounted optic can get in the way of some shooting positions. It’s a fairly common technique to rest a rifle sideways on a barrier to maintain the lowest possible profile. A side-mounted optic might prevent that.
Summing it Up
At the end of the day, you need to go with the option that best suites your needs and capabilities.
Assuming eyesight isn’t an issue here, I suggest this simple breakdown for AR-15 optics:
- 0-100 yards with priority on speed? Take a Class I Red Dot Sight
- 50-400 yards general field use and low weight? Class II low power fixed magnification
- Not concerned about weight, but need performance from 0 to 500 yards? Class III low power variable.
- Mid to long range precision? Class IV scopes.
- You won the lottery and want to invest? Angel invest for a Class V optic.
These rules are not hard and fast, so don’t go taking them as gospel. Given time, you’ll find that everyone has their own preferences and twists. The key thing is that you need to get out there and shoot.
Matt is the primary author and owner of The Everyday Marksman. He’s former military officer turned professional tech sector trainer. He’s a lifelong learner, passionate outdoorsman, and steadfast supporter of firearms culture.
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