Upgrading your AR-15 Optics

You’ve done your research, beat the shortages, and secured a reasonable amount of ammo and a few magazines. You went and bought your first AR-15.  

Now what? What else do you have to do before you can go shooting? You have to make sure you have some type of AR-15 optic to aim with. A staggering number of AR-15s sold today do not come with any sights, and there is a good reason for it. Individual preferences vary substantially, and the number of available options is downright staggering. The right choice depends on the gun's specifics, the application, the shooter, and budget!

I will do my best to walk you through the selection process and narrow things down a bit, and that has to start with the application.

The Application

You can spend A LOT of money on getting your AR optic set up just right, but in most cases, you do not have to. Rifle sights primarily fall into three categories:

1. Non-Focusing optics (red dot sights and holographics) 
2. Focusing optics (prismatic and conventional rifle scopes) 
3. Iron Sights

If this is a heavy barrel AR intended primarily for varmint shooting, get ready to spend some money. Good quality high magnification scopes are not cheap, but there are quite a few good options, and all you have to do is figure out what your budget is, allocate some extra cash for a high-quality cantilever mount, and go shopping. Look for a variable magnification scope with top-end magnification in the 15x to 30x range. It will be neither small nor light but on heavy barrel varminting ARs that is seldom a problem. The same set-up will work great for general purpose target shooting, but if you plan to participate in the new F-AR competition, you need to dial back on magnification a little. The rules only allow for 15x or less. 

I am a huge fan of 3-15x or similar rifle scopes on precision-oriented AR-15s. That is enough magnification for most things without making the scope too huge. An excellent example of a nicely optimized rifle scope for a precision-oriented AR-15 or AR-10 is the Vortex PST Gen2 3-15x44 if you are looking for a good FFP (First Focal Plane) scope that is not outrageously expensive. Still, there are plenty of good options from a variety of makers. With SFP (Second Focal Plane), Vortex Razor HD LHT 3-15x42 has a lot going for it, but there are quite a few good options from most manufacturers.

For anything involving precision, some amount of magnification is beneficial. The converse is true when you want to go fast. If your primary application involves speed and moderate ranges (say within 150 yards or so), you may not want any magnification at all. What you do want is a sight that is as easy to get behind as humanly possible. That is where red dot sights and holographic sights come in.

Non-Focusing Optics 

Aiming with one of these is like looking through a window, except the reticle is superimposed on the target. The aiming point can be a single red dot as in original reflex sights (that’s how the name Red Dot Sight came about) or a more complicated arrangement: dot inside a circle, illuminated cross, multiple dots for holdover, chevrons, etc. In the past, if you wanted something other than a dot, you went for a holographic sight with EOTech’s “Circle of Death” becoming justifiably famous for speed. However, nowadays, many reflex sights offer reticles with additional aiming points and/or circle-dot arrangements. While the always excellent Aimpoint reflex sights utilize simple dot aiming points, many competing designs offer extra reticle sophistication. SIG Sauer's Romeo 4H and 4T sights, for example, have switchable reticle patterns and a good number of manufacturers out there give you a variety of options when you order. A circle dot arrangement (Vortex’s and EOTech’s versions are shown below) is a little faster to acquire for many people, but that is very individual.

A switchable reticle pattern gives you more flexibility if you are not yet sure where your preferences lie. For example, here are the patterns available with SIG Sauer Romeo 4T and 4H. There are two models, each with four build-in reticle patterns you can switch between:

To me, holdover patterns are at their best when paired with a magnifier, but more on that later. Aside from the reticle patterns, holographic sights are powered via an internal laser that results in much shorter battery life than modern LED-powered reflex sights: hundred so hours vs. thousands or tens of thousands of hours. However, holographic sights offer an exceptionally undistorted view, virtually no measurable parallax, and coexist slightly better with astigmatism. This is where you pick your poison. If your astigmatism is severe, all non-focusing sights can give you trouble. Some reflex sights do not use batteries at all, like Meprolight’s battle-proven M21 equipped with a fiber optic collector for day use and a small tritium vial for night time illumination. The illumination is a little dimmer, but it works well, especially for those with astigmatism.

Aside from the reticle patterns and power sources, non-focusing sights can vary substantially in terms of physical size and window size, ranging from tiny open reflex sights that are at home on both handguns and ultralight ARs (Trijicon RMR, Shield RMS, Leupold Deltapoint) to slightly larger enclosed sights (Aimpoint Micro, SIG Sauer Romeo 4T, et al.) to full-size models (Aimpoint M5, Meprolight RDS). Most of these work well, and there is much personal preference involved in selecting one. Personally, for AR-15 applications, I tend not to go smaller than the enclosed sights like Aimpoint Micro. With full-size reflex sights, you can’t really go wrong with an Aimpoint, but I’ve become increasingly more partial to Meprolight RDS in the last couple of years. It has a somewhat different optical structure that minimizes forward light leaks and provides a very flat and undistorted field of view with still respectable battery life.

Astigmatism and Non-focusing Sights

Before I wrap up with non-focusing sights, I want to briefly re-visit astigmatism related issues. When I was younger, a red dot in my Aimpoint honestly looked like a dot. I developed mild astigmatism in my 30s. First, the aiming dot became a little elongated; then, it looked like a comet. Depending on which exact red dot sight it is, it can look like anything but a nice round dot with sharp edges. That makes precision aiming a little tricky. Many people have the same problem, and there are a few ways to deal with that.

Here is what I do: I don’t pay any attention to it. It makes no difference at CQB type distances, especially if you do not try to focus on the dot. Focusing on the target and the dot is sorta “just there”. At longer distances, you pretty much have to add an adjustable eyepiece magnifier to your RDS. Through the magnifier, the dot (or whatever the reticle happens to be) looks perfectly sharp. For close-range use, I either flip the magnifier to the side or remove it altogether. There are many excellent magnifiers out there, but the ones I tend to stick to are Vortex Micro 3x, SIG Sauer Juliet 4x and Aimpoint 6x, depending on how I use the rifle. Magnifiers shine with red dot sights that have some holdover features, like the Romeo4T mentioned above.

If your astigmatism is a little bit too severe to ignore or it irritates you, there are a couple of other things to keep in mind:

1. Keeping dot brightness a little lower helps keep the reticle pattern clean looking
2. Larger dots or patterns maintain good visibility even when they are not overly bright, so if you are looking to stick with a red dot sight despite your astigmatism, that is something to try.

Focusing Optics

If none of that works, you should focus on focusing sights, like prismatic scopes (ACOG, Elcan, SIG Sauer Bravo, Crimson Trace, SwampFox, Primary Arms, Vortex, Burris, etc.) and low power variables. Aside from being forgiving of astigmatism, they also offer distinct advantages for general purpose use beyond the close range.

The magnifiers I mentioned earlier, for all practical purposes, are just prismatic scopes without reticles. If you still want compact size and simplicity of fixed magnification, prismatic scopes are what you should be looking at. Easily the most famous of these is the Trijicon ACOG in use by the US military, closely followed by the Elcan issued by the Canadians and the Brits. These are excellent but expensive and somewhat flawed for aging civilian eyes. To make them as rugged as possible, and since most 18-year-olds going into the military have young and healthy eyes, both Trijicon and Elcan prismatic do not have adjustable eyepiece.

I can use my Elcan 4x and Compact ACOG 1.5x comfortably for now. Still, I am already beginning to notice that several less expensive prismatic scopes with adjustable eyepieces produce a little less eye strain for longer shooting sessions. The writing is on the wall that both of these will be transferred to my children before too long. The good thing is that there is a slew of new reasonably inexpensive prismatic scopes that do have adjustable eyepieces and perform at a level that was not attainable under $1k just 3-4 years ago. Another good thing is that there is now a good choice of magnification options available. Right now, I have SwampFox Blade 1x, Primary Arms GLx 2x, SwampFox TriHawk 3x, and Burris RT-3 3x sitting on my desk. All are under $400, and all are performing very nicely. If all you are looking to do is replace your reflex sight due to astigmatism issues, there are several very competent 1x prismatic scopes out there. The viewing perspective is slightly different from a prismatic, even if it is 1x, but the adaptation is rapid. Also, keep in mind that since prismatics have etched reticles, they work just fine even when your battery is dead.

If you are looking for some magnification, this is the situation where less is more. With prismatic scopes, to maintain a good field of view (FOV) with high magnification, the prisms grow in size almost exponentially. I recommend sticking to 4x or less most of the time. With brightly illuminated reticles, I can use the Bindon Aiming Concept (BAC) in reasonable comfort, for speed and 3-4x is sufficient to hit metal plates a few hundred yards out. I do have some set up with either offset or piggybacked red dot sight for close range.

Low Powered Variable Optics

If I want more magnification or more flexibility, I switch to LPVOs. Low Powered Variable Optics, or LPVOs, have undergone an incredible amount of development and optimization in recent years. It all started with S&B Short Dot 1.1-4x20 in the early 2000s and just exploded from there, with the progress made in the last 5-10 years being mind-boggling. For the sake of clarity, LPVOs are variable rifle scopes that start with 1x or 1.1x on the low end and go up from there. The first generation was mostly 1-4x designs, but that quickly evolved into 1-6x, 1-8x, and, most recently, 1-10x designs. They are not all created equal, but good ones are almost as fast as red dot sights on 1x and surprisingly competent once you ramp up the magnification. In terms of flexibility on a general use AR-15, LPVOs is the way to go. They will do almost everything that prismatic scopes will do, and almost everything that a red dot sight will do. For more money with some extra weight, LPVOs is a subject all onto themselves, and detailed coverage is beyond the scope here, but a few general guidelines are in order.

• Making a rifle scope work well on 1x is a little tricky, so if 1x is not critical, you will get more for your money with a conventional rifle scope that starts on 2x or higher.

• While high magnification ratios sound good on paper, there is no free lunch. It is better to have an excellent 1-4x than an average 1-6x or a poor 1-10x. They might cost the same, but they do not perform the same, especially on 1x. If you want a high magnification ratio AND good performance, prepare to spend some money.

• Proper set up of the adjustable eyepiece is critical with LPVOs, and you have to set it up so that your 1x view is as close to true 1x and as undistorted as possible.
• Pay attention to the diameter of the exit pupil on 1x. Many inexpensive scopes with high magnification ratios sacrifice that. You want it to be 8mm or higher for speed. 10mm or higher is better.

Given how many of these scopes are out there, I can’t quickly go over all of them, but I can tell you the ones I have used recently that I like.

• My go-to LPVO is the  Vortex Razor Gen3 1-10x24. It is not cheap, but it is excellent.  
• S&B Short Dot Dual CC 1-8x24 is probably the best, but more than double the price of the Vortex.  
• Vortex Razor Gen2 1-6x24, SIG Tango6T 1-6x24, Delta Stryker HD 1-6x24, and Steiner P4Xi 1-4x24 are around the $1k mark and perform exceptionally well. 
• On the lower end of the price spectrum, I have had excellent luck with Burris RT-6 1-6x24, HiLux CMR4 1-4x24, and SwampFox Arrowhead 1-10x24.

Iron Sights

Lastly, a few words about iron sights: the attachment to iron sights on AR-15s is almost romantic at this point. Unless you are going for a specific look or training young shooters, there is no good reason to keep your AR with iron sight only. There is a myth that they have a durability advantage to them, and it used to be true. Given how reliable modern good quality optical sights are, I am not so sure it still is. However, iron sights do make a very nice and low profile backup sighting system. If the optical sight you prefer is a reflex sight or holographic, iron sights can co-witness through it. However, with focusing sights, even 1x ones, that does not work. The most common setup is to have folding front and rear sights, with Magpul’s ubiquitous MBUS being the most affordable good quality option. However, many manufacturers make them, and if you do not need magnification, the most common set up is to have fixed iron sights co-witnessed through a red dot.

However, if you use a magnified optic, BUIS (BackUp Iron Sights) can only be deployed when the optic is removed. For those situations, I prefer to have them offset to the side to be accessed without having to remove the optic. Magpul and many other manufacturers make offset versions of their BUIS, but the ones I have been impressed with lately are the XTI sights from XS. Most commonly available AR-15 iron sights make speed compromises to get some extra accuracy. I think that is very outdated thinking. Iron sights, similarly to reflex sights, on modern ARs are there to get you out of trouble in a hurry, so I want speed above all else, and that is where XTI offset sights are ahead of the curve.

AR-15 Sights Budget Considerations and Wrap-Up 

To wrap all this up: 

• When choosing a sighting system for your AR-15, think of the application first and keep your budget in mind.   
• You can spend a lot of money on any of the optics types I mentioned, but it is much easier to stay on a budget with red dot sights and prismatic scopes. 
• The most flexible solution is the LPVO, but a nice one is rough on your wallet. Inexpensive ones can be hit or miss especially when it comes to speed on 1x.  
• Holographic or reflex sights will get you speed on a budget, but astigmatism can be an issue while extending the range can get tricky. 
• Prismatic scopes sacrifice some flexibility and are at their best when you want simplicity and an adjustable eyepiece. 
• Iron sights have been largely demoted into back-up use.

ILya Koshkin is a part-time gun writer and a full-time optics nerd. His work supports nearly every imaginable military imaging and targeting system out there.