An Intro Guide to Optics for the AR15: The Best Scope for your Rifle

We are re-publishing this classic guide with updates and new content for 2020! This is a guest post by Chris Hernandez. He is an all-around swell guy, author, police officer, veteran, and 2nd Amendment supporter. He has written an intro guide to optics. People new to the AR15 or shooting sports, in general, will find this article very useful. In this guide, Chris also recounts some of his experiences using these optics in a theater of war. No, he isn’t special forces, the beard was just part of the job.

A Primer on Optics for Your AR15

This isn’t intended to be a definitive guide on optics. If you’re already well acquainted with optics and want advanced information, there are many other writers and sites offering it. I’d highly suggest you go to one of them. But for the novice civilian shooters who have little time or money to train and no background in tactical optics, this information may be very valuable. Everything in this article is correct to the best of my knowledge, but if I’m wrong on something please call me out on it.

I’m not a sniper, nor do I have extensive experience with optics in the civilian world. What I do have, however, is a decent background in military optics from my twenty-plus years in the Marine Reserve and Army National Guard, including two combat deployments where I used an Aimpoint CCO (Close Combat Optic), Advanced Combat Optical Gunsight (ACOG), and Leupold MR/T (Medium Range Tactical scope). In the Marines, my secondary MOS was 8531, Marksmanship Coach. I’m also a school-trained Army Squad Designated Marksman (SDM), meaning I’ve attended a two-week course which taught me to hit man-sized targets with an M16A4 out to 600 meters with iron sights and ACOGs. So I’ve got a decent background in medium to long-range shooting, with and without optics.

This isn’t to say I’ve used these sights to shoot people. In Iraq my convoy escort team had roadside bombs go off around us and took sporadic fire, but never once identified a target and therefore never shot at anything. In Afghanistan, the only weapon I actually fired at someone was an M2 .50 caliber machine gun. I never had an enemy in my Aimpoint or ACOG sights. I did have Taliban in my MR/T scope three times, but every time I was denied permission to fire. And yes, I’m still mad about that.

So, first thing: If you’re a typical civilian shooter with limited training time and limited money for an optic and training ammo, there’s no reason to try to make yourself a sniper. It’s not going to happen. In the Army, with government ammo and decades of institutional marksmanship knowledge, the average soldier only shoots to 300 meters. And some of them struggle with that. So it’s not really feasible for the average civilian shooter, with extremely limited training resources, to expect to shoot like a sniper.

Second thing: For most modern combat, 300 meters is plenty far. I carried an M14EBR (Enhanced Battle Rifle) in Afghanistan, and I could consistently hit a torso-sized rock at 900 meters – at the range, with perfect weather conditions, a good firing position, on a stationary target at a known distance. In combat, with extreme heat or cold, unknown distances, hasty firing positions, adrenaline and moving targets, plus little annoyances like incoming fire, I would have been ecstatic to smoke a mofo at 200 meters.

Third: 300 meters is about the practical limit for civilians in any foreseeable domestic combat situation. If you’re preparing to defend your family from rampaging gangsters, it’s not likely you’ll find yourself sniping them from 500 meters. Urban combat is a close-in affair. In Iraq, enemy snipers sometimes engaged from within 100 meters. Unless you’re defending a farm in the middle of acres of cleared land, you probably won’t do any long-range shooting.

With that said, here’s what I think a newcomer should know about tactical optics.

“Red Dot” Optics


A red dot optic isn’t a “telescope” and has no magnification. Red dot sights like the Aimpoint and EOtech project a holographic dot or circle onto a lens; if you’ve properly sighted your optic, the dot replaces your front sight tip centered in the rear sight aperture. Instead of having to line up your sights on the target for every shot, you place the dot on it. Generally speaking, red dot sights allow a shooter to get on target much faster, especially in reduced lighting.

While red dots are often referred to in the military as “close combat optics”, they’re practical for shooting to at least 300 meters, just like iron sights. They have no quick adjustments; if your red dot is zeroed military style, it will hit dead center at 30 meters and 300 meters. Between those distances, it will hit high, further than 300 it’ll hit low. The dot DOES NOT have to be lined up with the front or rear sight (I’ve seen soldiers make that mistake more than once).

The size of the dot or circle is a consideration. Generally speaking, a smaller dot allows for better accuracy, a larger dot is better for close-range engagements. EOtechs have a large circle around a small aiming dot; the large circle can be used as an aiming reference on a human target in, for example, room-clearing (rather than trying to get a dot center mass before shooting, you’d just get the big circle onto your target’s torso). Aimpoints and other optics, like the JPoint, just have a dot.


eotech mock up

The real beauty of red dot sights is that they allow shooters to keep both eyes open. In real combat, when you’re probably already experiencing tunnel vision, you really don’t want to lose even more vision by closing one eye and lining up a dark front sight tip within a narrow rear sight aperture. If you’re scanning a room with both eyes open, weapon at the low ready, and an enemy suddenly appears in a doorway, you’d simply lift your weapon to your shoulder, acquire the bright red dot, place it center mass, and fire.

The dot doesn’t need to be centered in the scope, either. If you’re in a firefight, flop down behind cover and find yourself in an awkward firing position with your head canted and the red dot close to the edge of the scope tube, your round will still hit where the dot is. This is what parallax-free means for practical shooting, but with some caveats.

Aimpoints, EOtechs and a few other red dot sights are robust, proven and reliable. Their battery lives can be literally years long. They can be dropped, kicked and banged around without losing zero. While they’re the cheapest among the optics I’m discussing here, they’re not free; a decent red dot sight will cost about $400. There are plenty of indecent sights that are much cheaper. Those sights are great, as long as you don’t mind not hitting what you’re aiming at. Ask me how I know.

As a final note, red dots should always be used with backup iron sights (BUIS). No matter how reliable, technology fails. Optics get damaged or covered in mud. Batteries die. If you mount a red dot, have BUIS zeroed with it. When my Aimpoint is mounted, my BUIS are always up. When I’m looking at the red dot, the backup rear sight blurs out. If I raise my weapon and realize my red dot isn’t there because of a dead battery or whatever, I can immediately switch to the BUIS. Besides that, if your BUIS and red dot are zeroed to the same distance, you can use your BUIS to do a quick zero confirmation on your red dot. Just flip your sights up, center your front sight tip in the rear aperture, ensure your red dot is on the front sight tip, and you’re confirmed (as long as you’re sure your BUIS are properly zeroed).

The Trijicon ACOG

Trijicon Acog

I love ACOGs. An ACOG is a very sturdy, accurate, and easy to use fixed magnification sight with an illuminated reticle. Trijicon now makes many models of ACOG with different reticles for different weapons, calibers and barrel lengths. I trained on the basic TA-01NSN, and that’s the one I’ll discuss.

The TA-01NSN has a simple crosshair reticle instead of a chevron, a big V, which in my opinion makes it a little better for distance shooting. It also has a very simple bullet drop compensator (BDC), which is a series of smaller aiming points below the main crosshairs, calibrated for distances from 100 to 600 meters. It’s designed for an M4 carbine, but we used them on M16A4s at SDM school. Because the shorter-barreled M4 has a different bullet drop than a standard-length M16A4, we couldn’t just zero our weapons at one distance and expect them to be accurate all the way out to 600 meters. So we did what every ACOG user should do.

TA01 Tritium ACOG low light

TA01 with tritium illumination at night

We zeroed our weapons at each range line, from 100 to 600 yards. You’ll notice I said yards, not meters; although the ACOG is calibrated in meters, almost every military known distance range was built in yards. And the military isn’t going to rebuild every range. When we fired at 600 yards, the meter distance was about 550. Since the ACOG’s BDC didn’t exactly match up with the range lines, we had to fire at each range and record our sight picture for each. The sight pictures weren’t always what you’d think; for example, if I recall correctly, at 400 yards we’d put the 300 meter crosshair onto the target’s head. Then we drew each sight picture on a notepad, and also drew them on our rifles with white-out. During the qualification tests, when we determined our target’s range we’d simply refer to our predetermined sight pictures.


TA31F with Fiber optic illumination

…And speaking of determining range, the ACOG is a fantastic tool for it. The horizontal line on each cross-hair corresponds to the average width of an adult male across the shoulders. So if you see an enemy at an unknown distance, you guess roughly how far away he is, then put the horizontal cross-hair line across his shoulders. Let’s say you thought he was about 300 meters away, so you used that line. That line was too long, meaning he’s further than 300. So you switched to the 400-meter line. It was just about the right length. So he’s approximately 400 meters away. If 300 is too long but 400 is too short, he’s between those distances. Too easy.

ACOGs can be bought with built-in BUIS, or with a small red dot sight mounted on top. If you don’t get those accessories, mount BUIS under the eyepiece. If your ACOG is damaged or unusable for any reason, you can detach it and use the BUIS.

A new TA-01NSN costs about $1000. I got one used for $600, six years ago. ACOGs are serious pieces of equipment, they’re not for the guy who fires a magazine from his AR-15 at a 25 yard range twice a year… And they don’t exactly make distance shooting “easy”; one common observation about the ACOG is that at longer ranges, the shooter will see every little movement he makes, and can “psych himself out” by thinking he’s all over the target. In reality, he’s not moving any more than he would if he was using iron sights. But with the ACOG every movement, including the movement induced by the shooter’s heartbeat, is visible. Because of that, some students in my SDM class actually did worse with an ACOG than they did with iron sights.

And as a final note, don’t zero your ACOG at 25 meters. Most Army units haven’t quite figured this out yet, but parallax isn’t eliminated in an ACOG until you’re at 30 meters. So if you can only zero at one distance, make it 100 meters.

The Leupold MR/T:

Leupold MRt Scope

When I was a teenager, I mounted an El Cheapo hunting scope to my old AR-15A2, because I thought it looked cool. And for the time, I guess it kinda did. Then I tried to shoot with it. And not only could I not hit crap at a distance (because I didn’t zero it correctly), I couldn’t even see a target close in. So the scope came off.

Now I know a little more about traditional scopes. They’re great, but only for distance shooting. They interfere with close-range target acquisition. They’re generally not built to withstand the rigors of combat. You don’t want one on your primary battle rifle unless it’s sturdily built and backed up with a red dot sight. If I was going into a situation where the enemy could be either 800 meters away or across a room, I wouldn’t even consider mounting a traditional scope.

But traditional scopes have their place on a battle rifle. If their capabilities are understood and they’re used the right way, they’re invaluable.

Of the three optics I’m discussing today, the Leupold MR/T is the one I have the least training on, but oddly, the most operational experience with. There are different MR/T models, mine was 3.5 to 10 power with an illuminated reticle. I came to be issued an M14EBR with an MR/T through an odd military circumstance; I trained on an M16A4 with ACOG before Afghanistan, and I requested that the unit issue me one. The unit had them, too. But the other Designated Marksmen and I were told, “No, we’ll get you M14s and training before we deploy.”

We did eventually get M14s. Months after we got to Afghanistan. With no training on them at all. So I went to the only guys around who might be able to train me, which were a retired SF sergeant and the French Marine sniper team on my firebase (and before anyone says it, the French are great soldiers). They got me zeroed at 300 meters, and I learned that the dots below the crosshairs roughly corresponded to 200 meters increments; the crosshairs were 300 meters, the first dot below that was 500, next one 700, and so on. At the firebase range, I could consistently hit the rock I mentioned earlier at around 900 meters.

But still, I considered not taking the M14 on missions, because I wasn’t really confident with the scope. I was, after all, untrained. But I considered the capability of the M4’s round versus the M14’s, and the fact that our engagements were usually at 300 meters or more. I also had a red dot JPoint sight mounted on my Leupold, plus a white/IR light, so I could use it for room-clearing if necessary. I decided to trust the M14 and MR/T.

As I said before, I had Taliban in my scope three times. Each time they were 700-900 meters away. Once four of them were crossing an open field, and I thought, I got this. Even if I miss 15 times, eventually I’ll get lucky and hit one. But we were denied permission to fire every time.

However, I did get an opportunity to show off my skills once. I was at a tiny outpost with other Soldiers, American, French Marines, and Afghan troops. A US Marine colonel asked how accurate my rifle was. I told him it was good to about 900 meters. He picked out a man-sized rock in an open area, about 800 meters away.

“Can you hit that rock?”

I nodded, “Oh sure, no problem sir.”

“Go ahead, shoot it.”

I still wasn’t real sure how good I was with the weapon and scope. But I got into as steady of a position as I could, went through the Breathe-Relax-Aim-Stop-Squeeze process, and fired.

A Marine sergeant was watching through binoculars. I looked at him. He squinted, shook his head and said, “I didn’t see the splash. Try again, but shoot just left of it.”

Oh, crap, I thought. I might have missed so badly that the round didn’t land anywhere near the rock. But I aimed to the left of the rock and fired. Dirt popped up about a foot away.

“Yup, right where you aimed. You hit the rock with the first shot, I just couldn’t see it.”

I hit the rock again, just to show off. The sergeant saw that one. Several spectators expressed admiration. I acted like it was no big deal. Inside, I was relieved. If I had blown that shot, I would have been fatally embarrassed.

I handed the colonel the rifle. “Go ahead sir, try it yourself.” Then, acting like I was some kind of expert, I said, “You see the dots under the crosshairs? Just put the second dot at the top of the rock.”

The colonel fired. And hit the rock with his first shot.

I tell this story not to brag, but to illustrate something about the Leupold. Even with no real training on that scope, even with only the most basic guidance on its use, I was still accurate to 900 meters. The colonel, who as far as I know had no advanced marksmanship training, hit a target at 800 meters with it. That’s impressive.

A Leupold MR/T can cost about $1500. And it’s worth every penny. As long as you put the time, effort and ammo into learning how to use it.

Bottom Line: Which Scope Should I Choose?

A variety of quality optics exist which can help the novice to be a better tactical shooter. These optics aren’t interchangeable; each different class serves a specific purpose. They’re not cheap either. A quality optic will cost at least several hundred dollars. As with everything else, with optics you get what you pay for. If you go cheap, don’t expect accuracy. When your life is on the line, zeroed iron sights are about a billion times more valuable than a cheap Chinese knock-off ACOG that makes your rifle less accurate than a Derringer. So get a good optic and zero it properly. Keep your iron sights zeroed as well. And most importantly, train, train, train.

Chris Hernandez is the Author of the following books: Click the covers to check them out on

Line in the ValleyProof of Our Resolve