When it comes to AR-15 and the myriad of choices you have to make, things can get overwhelming. A lot of folks get wound around the proverbial axel over things like barrels and triggers, and rightly so. But if you’ve read my guides on those topics, you also know that I think a lot of folks overthink it. AR-15 optics are similar. But when it comes to optics, I’d say that you get far more return on your investment for more money spent.
At least to a point.
There’s a lot of misunderstanding and “fluff” out there regarding rifle optics, especially the tactical variety. I want to take a few moments and discuss some thoughts on selecting an optic for your AR-15.
There are already some really great guides out there. My observation, however, is that they focus more on particular classes of optics. Rather than thinking about all of the considerations that go into picking the right class for you.
This post is more like a broad overview of how to think about each type of optic and what you would use it for.
Here’s the thing: the “best” AR-15 optic is a moving target that shifts every year as new products come to market and fads change. You’re far better served thinking carefully about your own real-world needs and picking a quality optic that matches your needs.
That quality AR-15 optic will serve you for years and years just fine, and there’s no need to chase the latest and greatest. Don’t think that means I won’t provide some suggestions, though. I’ll include some of my favorite optics from each category as we go.
Speaking of which…
A Refresher on the Basics
As a reminder from my other articles on picking AR-15 accessories, 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, let me give you a quick recap.
The actual purpose your weapon fulfills drives the choices you make.
Too many people buy something because the internet told them to, and then try shoehorning 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 AR-15 optics, or really rifle optics in general, 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 the last 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. The Army’s been putting out industry requests for years on the topic, but nothing has materialized so far.
With that, let’s dig into the first category of AR-15 optic, the iron sight replacement.
Class I Optics: Replacing Iron Sights
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, though 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 focus on the target. The optic projects a dot onto the same visual plane.
The key benefit here is simplifying the act of obtaining a sight picture.
This class of rifle optic rose to prominence during the early 2000s. The intense CQB/urban operations in Iraq 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.
RDS Employment: Set and Forget
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 all, and will use fiber optics and tritium for illumination.
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-purpose 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.
This affects me for all of my illuminated optics, not just red dot sights. I find that battery-powered illumination is slightly worse than fiber optic.
The lack of magnification in this category of AR-15 optic also means it’s not ideal for observation and identification. Furthermore, Class I optics are not designed for easy zero adjustments in the field.
It’s all Kentucky Windage, all of the time.
Class I AR-15 Optics Roundup
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 field use. They are typically compact, relatively lightweight, rugged enough to put up with the abuse of infantry life, and offer huge marksmanship benefits over iron sights.
The reticles in these optics usually have some form of range-finding stadia and a calibrated bullet drop compensator (BDC). These are field-expedient methods of estimating where hits will land and not intended for true precision shooting.
The BDC reticles are not terribly precise, usually matching to a specific bullet moving at a specific velocity under specific environmental conditions. Deviating from these standards means that the BDC is not correct, but should still be “close enough.”
I would venture to say that Class II optics embody the skillset of a traditional rifleman. They are fantastic for fighting in the open in distances between 50 and 300 yards.
But they lose out to Class I optics when it comes to close-in fighting.
Class II optics truly reward proper execution of marksmanship skills. 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 like a red dot sight.
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. You might notice a shift between POA and POI when using this method. It’s a genetic factor that’s different for everyone.
You see, your eyes aren’t always looking at the exact same point all of the time. When you stick magnification in front of one eye and not the other, the effect gets worse. This is “phoria” and usually means that the Bindon Aiming Concept isn’t terribly useful beyond CQB distances for people like me.
Like all magnified optics, Class II AR-15 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.
You might wonder if Class II optics still have a place in a world where we have very fast Class I optics and super-versatile Class III optics, which I’m getting to in a minute. We had that very discussion in our forums, and the conclusion was “Yes. Yes they do.”
The key benefit of Class II optics is their light weight and durability. As much as I like my ELCAN and TA110, I have a hard time justifying them over a Class III LPVO given the weight. However, a compact ACOG like this is perfect for the job.
Class II Ar-15 Optic Roundup
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 300 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 dominating the market. Class III AR-15 optics bridge the differences between Class I and Class II categories.
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 range.
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 cowitness through Class III AR-15 optics.
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 or offer even more.
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 IV AR-15 Optic Limitations
Class III AR-15 optics are heavier than either Class I or Class II options, usually weighing 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 mount.
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 Roundup
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 optics, but are heavier and less durable unless you want to step up to much higher prices. Now whether or not you actually need that increased durability is another question. Most of the mid-range optics in the $700-$1500 are fantastic and will serve you well.
To be honest, it's hard to pick a single winner in this category, especially because the price ranges vary so much. But if I had to pick one, it would be the lesser-known SWFA, which has a great combination of ruggedness, optical clarity, and intelligent reticle design
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 than anything else.
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 notice, like your heartbeat or muscle tremors, become readily apparent and frustrating from unstable positions.
For this reason, Class IV optics are mostly limited to supported positions where you can mitigate these instabilities.
Are better, fancier, more advanced scopes available? Yes, of course. But I think this one is hard to beat when it comes to balancing cost, quality, and performance. Really, you should consider the entire PST line, depending on your needs.
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.
Combining two different AR-15 optic types on the same rifle helps provide the “best of both worlds,” but you have to give something up in return. This compromise usually shows up as ergonomics.
As an example if you mount a miniature red dot on top of a Class II optic, you will sacrifice a solid cheek weld to use it. It’s simply too high over the bore to keep that solid position.
That may not be a big deal at close ranges, but it’s not the optimal way to use it.
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.
Moreover, that offset-mounted optic can get in the way of some low-profile 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.
The same thing applies to flip-to-side magnifiers. They are certainly useful for what they are, but be aware of the compromise they bring to the table.
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.