All About Precision Riflescopes

Here’s a crash course in tactical precision optics. Buckle up!

All About Precision Riflescopes

A decade ago, I was fortunate enough to spend some quality trigger time with a couple of world-class long-range shooters: Scott McRees, owner of McRees Precision, and Chris Reed, winner of Top Shot Season 2 on History Channel. I was there to test a McRees Precision BR-10 .308, built on a plain-Jane Remington 700 short-action, with a McRees-finished match-grade barrel and a Timney 510 trigger. For all intents and purposes, the rig was a work of art, and rifles seated in McRees Precision chassis had already taken national sniper matches.

I walked onto Scott McRees’ range with a 4-24x56 second-focal-plane riflescope I had just received for editorial review mounted on the new BR-10 and learned a hard lesson. From the first shot, I wished I had studied the riflescope’s features and better understood the shooting environment. The scope I used for the day was completely under-equipped. The problem wasn’t simply a second-focal-plane reticle or even the realization that some targets were at unknown distances. It was worse. The reticle was mil-dot, but turret adjustments were MOA. I ended up with a reticle drawing on a piece of paper with holdovers awkwardly noted in various positions between subtension lines. To be sure, it was a lackluster day of shooting, and I have been sensitive to ensuring I use the right optic for the job since then.


If You Sell It, Know It

Perhaps the most critical issue in all of this was the lack of optic knowledge from the manufacturer representative. He sent a scope with a mix of MRAD and MOA, completely different measurement values. Of course, shame on me for not studying the optic and recognizing the problem before I pulled up to the range. At the same time, I should have been able to count on an optic company’s representative to know the optic he sent for long-range shooting was fundamentally flawed. Just as bad, and more impactful for retailers and the customers you serve, many retail counter reps don’t know or understand optic systems either, but they are acting as the company’s experts in recommending optics to consumers. Therein lies a major issue. A representative’s lack of optic knowledge can destroy a retailer’s credibility or improperly equip a shooter, and both are bound to learn hard lessons.

In the spirit of “knowledge is power,” retailers and employees alike should take ownership of training, resources and basic understanding of key components. In the firearms industry, understand differences, basic mechanic principles and purposes of products like revolvers, hammer- and striker-fired handguns, bolt-action rifles and semi-autos, target and hunting munitions and even basic riflescope characteristics, the subject of this article. To that end, I hope the information here also serves as a reference.



MOA and MRAD are the two most popular rifle optic measurement values used today, with IPHY coming in a distant third place. To keep readers from getting lost in the forest of rocket-sciency optic info, I hope to keep the difference simple. All measurements are based on angles; in fact, MOA is literally the abbreviated term for minute-of-angle.

Using the KISS method of explaining values, 1 MOA is 1.047 inches at 100 yards. This is called true MOA, or TMOA. Many call out 1 MOA simply as 1 inch at 100 yards. This is called shooter MOA, or SMOA. Truthfully, shooters are not necessarily wrong to call it an MOA out that way, since extended out over 1,000 yards, the difference between TMOA and SMOA is just .47 inches. Even at 2,000 yards, the difference is still less than an inch. Of course, most MOA riflescopes incorporate 1/8-, 1/4- or 1/2-MOA-per-click turret adjustments. Using 1/4-MOA-per-click as the example, on elevation or windage, one click moves the point of impact .25-inch at 100 yards, 1.25 inches at 500 yards and 2.5 inches at 1,000 yards — this math extends out over distance.

With such a subtle difference between MOA and IPHY, MOA is essentially the IPHY killer. Bottom line: You’re not likely to carry a riflescope with IPHY values because MOA is too close and too popular. Moreover, IPHY is not likely to ever replace MOA because most MOA shooters already employ IPHY math via the simplified SMOA conversion. It really come down to what is already out there and popular.  

MRAD, also known as mil, is a bit different. Either abbreviation is short for milliradian. Milliradian is one-thousandth of a radian, but I risk overcomplicating here. What is important is to understand that 1 mil is 3.6 inches at 100 yards. For better perspective on why mil is so popular internationally, 1 mil also is 10 centimeters at 100 meters. Most mil scopes feature .1-mil-per-click turret adjustments. This equates to .36-inch per click at 100 yards or 1 centimeter at 100 meters. Obviously, working with yards is most popular with American shooters, so we’ll extend math out in inches.

While one click (.1 mil) adjusts the point of impact .36 inches at 100 yards, it adjusts POI by 1.8 inches at 500 yards and 3.6 at 1,000 yards. Again, the math extends in the same manner over distance. To simplify, as we do in SMOA, many shooters dumb down mil/MRAD math as three clicks (.3 mil) equals 1 inch. This is close, since .3 mil actually equals 1.08 inches at 100 yards. Like SMOA, simplifying mil math in this manner is inconsequential at closer range but can start to take on much larger meaning at 1,000 yards — the guestimate would be off .8 inches at 1,000 yards, nearly a full inch. Shooting at 2,000 yards, the math would be off 1.6 inches. Still, for most shooters, simplifying math definitely provides close-enough results.


Second-Focal-Plane Reticles

Knowing MOA and MRAD/mils values is key to understanding reticle subtensions based in those systems (not including simple crosshairs or bullet-drop-compensated reticles calibrated to specific loads). Considering scopes specifically utilizing MOA or mil subtensions, MOA optics are still the most popular for most shooters, although mil-based optics are incredibly popular among precision long- or extreme-range shooters. Using MOA or mil is largely subjective — depending on which math is easier for the shooter. Differences between second-focal-plane reticles vs. first-focal-plane reticles are less subjective and more purpose driven. Let’s look at second-focal-plane reticles first.

The most popular reticle system today is on the second focal plane. Part of SFP popularity simply rests in cost. Optics with first-focal-plane reticles generally cost quite a bit more than SFPs. Additionally, many shooting enthusiasts are shooting at closer range. The advantage of a reticle size that does not change whether a shooter sets the magnification power on the lowest or highest setting has an obvious benefit — you’ll understand this when I explain FFP reticles a little further down. Many long-range shooters engaging targets at known distances, especially in slow-fire scenarios, choose SFP reticles, but with more powerful magnification ranges.

So what is the downside of a second-focal-plane reticle? For shooters who depend on holdovers rather than turret adjustments, or who are shooting targets at unknown distances, a SFP reticle system is a nightmare. Since the reticle size does not change throughout the scope’s range of magnification, the subtension values (indicated by those pesky hashmarks) are only accurate (to MOA or mil) at one magnification power — most often the highest power. At every other magnification within the scopes range, the subtensions are not accurate.


First-Focal-Plane Reticles

In the word of dynamic long- and extreme-range precision shooting, especially when engaging targets at unknown distances, first-focal-plane reticles reign supreme. Unfortunately, they often demand a supreme price tag — some FFP riflescopes can cost in excess of $5,000. Obviously the target market for those pricey optics is incredibly small; however, a number of reliable optic companies now produce solid-performing FFP scopes with lifetime warranties for $500 to $3,000. Today, there truly is a FFP option for everybody.

So, what is so great about a first-focal-plane reticle? A reticle on the first focal plane increases or decreases in size commensurate with magnification power. Increasing magnification power enlarges the reticle. Conversely, reducing the magnification power reduces the reticle size. Of course, this is why closer-range shooters and hunters prefer a SFP reticle. At a low magnification power, the reticle can become quite small and much harder to read. For that same reason, however, long-distance shooters love FFPs — but there’s more. Since FFP reticles increase and decrease with magnification, the MOA or mil subtension values remain accurate throughout the power range. A 1-mil hashmark at 5X still represents 1 mil at 25X.

Consistently accurate subtension values throughout the magnification range play a major role in engaging targets and unknown distances — the reticle actually becomes a rangefinder. If a shooter estimates a steel target at 18 inches and it fills a .5 mil of subtension space, the target is approximately 1,000 yards away. A hunter settling a reticle on a coyote can guess 20 inches to the shoulder. If the coyote fills 1 mil from the bottom of the hoof to the top of the shoulder, his distance can be estimated at 550 yards. Understanding what measurement values subtensions convert to makes ranging easier. This is how many top-level shooters hit targets at varying unknown distances quickly. It would be difficult at best to attempt this type of shooting with a SFP.



In most cases, customers are after variable-power scopes, meaning the optic includes an adjustable range of magnification power. Occasionally, for close-range setups, including shotguns, consumers are after a fixed-magnification optic. This means the optic has a magnified field of view and it cannot be adjusted. One more scope option to consider for close- to mid-range shooting is a low-power variable optic, also known as a LPVO. As the name implies, a LPVO’s magnification range generally begins at 1X and caps out at 4X or 6X, although some great models are currently on the market boasting 8X and 10X. These optics most often feature what is routinely described as tactical-style — a standard-size eyepiece assembly, straight tube and 24mm objective lens. Many lower-powered riflescopes do not include parallax adjustment (side focus).



Parallax is the condition where the reticle and the target are not on the same plane. This is most recognizable by rocking the head while attempting to keep the reticle on target. If parallax is an issue, the reticle rises above and falls below the point of aim. Again, this is the result of different planes. Many of today’s scopes, including most high-powered variable optics, include a parallax adjustment, also commonly known as a side focus. I correct parallax with a side-focus knob by turning it as I pivot my head up and down while keeping the reticle on target. When the reticle stabilizes on the target and the field of view appears clearer, my parallax is adjusted properly. Most parallax/side-focus knobs include yardage marks.


A Bit More Clarity

Zeroing a scope is a process of sighting an optic in, most often at 100 yards, and then adjusting the elevation and windage turret knobs (not click-adjusting the actual turrets) to read zero. Most often this is accomplished by loosening or removing the turret knobs, turning them to face zero and the tightening or reinstalling.

A zero stop is a feature in many long-range precision riflescopes. When turrets are zeroed and a zero stop is set, the zero stop keeps the turret adjustment from dropping below zero. If I was shooting at 900 yards and wanted to dial back to double-check my 100-yard zero, I would only have rotate my elevation down until the turret stopped. I would then be at a 100-yard zero again. Not only is a zero stop a quick way to return to zero, but it also prevents getting lost in turret rotations.

The most recognizable parts of a riflescope not already covered, from back to front, are the diopter (fast focus), ocular lens, eyepiece assembly, magnification ring, rear scope tube (housing erector lenses), turret adjustments, front tube, objective bell and the objective lens.

No, tube diameter doesn’t affect light transmission. I hear this point often. “It has a 30mm tube, so it’s great in low light.” Truth be told, a larger tube primarily allows for more robust and finer turret adjustments. What enhances field of view in low light is a combination of quality glass, a scope’s exit pupil and the objective lens; in fact, coated glass can enhance lighting, too. In a nutshell, the larger the objective lens and the smaller the exit pupil, the better lighting in the field of view. As an example, a scope with a larger objective lens, set at a lower magnification power, would be optimum for a lower-light environment.


Purpose-Driven Decisions

At the end of the day, everything mentioned here comes down to one thing: purpose. Being armed with knowledge like MOA, mil, FFP and SFP differences, riflescope components and the roles they play, and a customer’s purposes for an optic makes it much easier for an employee to make legitimate recommendations that not only properly equip them for their tasks but also create trust… and repeat customers.



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