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Rifle Scope Terminology: Parts, Settings, and Definitions

1_Rifle Scope Terminology

There’s no better way to dive into a new hobby or skill and level up from rookie to an expert than to learn its jargon!

The same goes for your rifle scope; if you are new to hunting, shooting, or guns, you’ve come to the right place!

I understand that scopes are quite technical. I know the frustration of having so many words to learn that I just couldn’t keep track of it all.

I’ll try to make the hassle of learning all the rifle scope terminology a little easier for you.

Rifle Scope Terms and Definitions: A Beginner’s Guide

Armed soldier

This glossary lists some commonly used terms and definitions of rifle scopes to help you get started on your hunting journey!


Ballistic Aiming System (BAS)

This system was developed by Leupold, one of the most popular optics companies.

It integrates ballistic reticles and ballistic turrets for an accurate dead-on-aim shot no matter what, where, and when you are hunting.

Ballistic Coefficient (BC)

BC measures the capacity of a bullet to overcome air resistance when fired. The higher the BC, the less velocity a bullet loses in flight.

Manufacturers of bullets will typically publish the BC of their bullets.

Ballistic Programs

These programs may also come in the form of online services that offer specific tools to calculate holdover values for scopes and cartridges.

The program will need additional information, such as bullet ratio, sea level, and wind speed, to arrive at this measurement.

If you don’t really want to do computations (like me), you can refer to one of these programs.

Ballistic Reticle

The ballistic reticle considers BDC technology to correlate angles, atmospheric conditions, ammunition data, and angles to achieve an accurate aiming point.

I use ballistic reticle to predict the measurement of a bullet’s flight at a certain angle.

Ballistic Turret

This feature allows you to set preset distances, eliminating the need for ballistic reticles and removing the uncertainty of distance estimation.

It’s a common feature among expensive and higher-end riflescopes.

Bullet Drop Compensation (BDC)

Contrary to what a beginner might think, a bullet doesn’t actually travel in a straight line; it eventually curves downward because of gravity.

BDC is the relationship between the fired bullet, its target, and gravity.

Rifle scopes can opt for a BDC reticle or ballistic turret to improve the effects of gravitational pull over a traveling bullet.

This improves the bullet’s reaction to air resistance, thus, improving bullet velocity, and getting you well-placed shots every time.



It refers to cartridges (or ammunition) of almost all shotguns, rifles, and handguns.

The term also refers to the position where the gun’s firing pin strikes the bullet base, which is the catalyst to the chain of events leading to the shot.


You will hear a click sound when you adjust your windage and elevation turret.

Each click changes your scope’s point of impact by less than an inch, depending on the distance.

Simply put, clicks are the number of revolutions on the turrets used to adjust your aim before shooting.


Specialized chemical coatings are applied to the lens of rifle scopes, laser rangefinders, binoculars, or other sports optics.

The thicker the coatings, the lesser the glare and reflectivity resulting in a clearer image for the users to see.

You have your choice of fully-coated lenses or fully multi-coated lenses.

When you buy your first scope, I recommend going for fully multi-coated lenses as these are the most effective in giving you a CLEAR image.

These coated lenses work to reduce light loss and glare caused by reflection. It also allows for lesser eye strain.

Take note that the MORE coatings your rifle scope lens surface, the costlier it will be.


Duplex Reticle

This is the most common choice of reticle for entry-level rifle scopes and my reticle of choice!

It features crosshairs reaching the edges of its field of view.

When its crosshairs meet like a “T” in the center, the thickness of the posts becomes finer.

Although, each duplex reticle style may differ slightly per optics brand.


Eye Relief

Have you ever had your rifle’s recoil hit your eye because it was too close to the scope? I have.

That’s where eye relief comes in!

This is the measure of the suggested distance your eye must position from the ocular lens and still get a good field of view.

Otherwise, your scope’s recoil would hit your eyebrow and leave a nasty mark. Ouch!

My ideal eye relief would be around 3.5-4 inches.


Fast Focus Eyepiece

This European-style eyepiece technology allows you to focus on the grid to see a sharp and crisp image in the reticle with only a fraction of a turn focal length.

The Fast Focus Eyepiece focusing speed rate is much higher compared to traditional non-fast methods.

However, it does not have the locking mechanism of these standard methods.

Field of View (FOV)

The FOV is the amount of area you can see within 100 yards through your scope. This is typically measured in feet and is dependent on magnification.

As magnification is increased, FOV is lessened, and vice versa.

A typical 3X variable rifle scope will have a FOV at 100 yards of 30 ft. At 9X, the FOV at 100 yards will be at 14 ft.

Even if you have a larger objective lens diameter, these numbers will not change.

First Focal Plane (FFP)

The first or front focal plane describes the reticle’s position.

With FFP scopes, its subtension stays the same while the crosshairs increase in size as the magnification increases.

FFP scopes are most useful for competition and long-range shooting.


Hold Over/Under

Remember when I said bullets eventually curve downward?

If that’s the case, you need to adjust your rifle scope a little higher to compensate for the effects of gravity, which is holdover.

If you want to hit directly at the bullseye, you may need to aim your crosshairs a bit higher.

Hold over/under measures the amount of point of aim change from your target’s position.

This can be above or below your target, to which you require scope adjustments to coordinate with the bullet’s trajectory.


Light Transmission

Light transmission measures how much light your objective bell collects and transmits to the eyepiece of the rifle scope for the human eyes to see.



Magnification is also known as the power rating of a scope. Your magnification settings are defined with an “x.”

For example, a 10x is a 10-power scope.

This means the objects you are seeing are ten times closer than how you would see them with the naked eye.

A magnification setting will be read in the following manner: 3×9, meaning your rifle scope has an adjustable magnification range of 3 up to 9 power.

For long-range shooting, go for 9-12x scopes. You may also opt for fixed-powered scopes if that is your preference.

I prefer having variable magnification (more than one) over fixed (only one) because it gives more range and versatility when target shooting.

Maximum Point Blank Range

Maximum Point Blank Range refers to the LONGEST possible distance a shot can travel without going above or below.

Milliradians of Angle (MIL/Mrad)

MIL is the measure that determines the correct correlation and windage adjustments to see through your scope properly.

It is mostly found in European-based optics.

Minute of Angle (MOA)

Just like MIL, Minute of Angle measures correct windage and elevation adjustments to view your scope. 

MOA is a unit of measurement of a circle, one-half inch at 50 yards, 1 inch at 100 yards, 2 inches at 200 yards, 5 inches at 500 yards, and so forth.

It does not necessarily measure distance but rather an angle in the scope that translates to a certain size at a distance.

Muzzle Velocity

This is the amount of speed at which the bullet leaves the rifle’s muzzle. It is measured in feet per second (fps) or meters per second (mps).

This information is integral in ballistic calculations.



Parallax is the reticle’s position on the target image at different focal planes.

Have you ever looked through your scope and saw that something was off with your target and reticle?

You might have seen your reticle move whenever your move your head or eyes.

It is the reason why you can’t focus on a close and distant object at the same time at a certain distance.

Most rifle scopes without an adjustable objective are preset at 100 or 150 yards, so your target and reticle will focus simultaneously to allow a parallax-free sighting.

Point of Impact (POI)

The point of impact is the literal point where the bullet strikes the target.

When adjusting for your scope’s correct setting, make sure they are set to arrive at your desired point of impact on the target.



This measures your device’s capability to produce a sharp image with fine detail to be seen by the naked eye.

The quality of your scope’s coatings, precision manufacturing, atmospheric conditions, and the user’s visual acuity determine your resolution.


A reticle is composed of lines, dots, and crosshairs in your scope. These are superimposed on the target you are viewing.

The most common designs are the rear focal plane or the second focal plane.

The reticle, in this case, is behind the magnification adjustment, meaning that no matter the magnification, your reticle size stays the same.

The front or first focal plane does the exact opposite.

When the reticle is in front of your magnification adjustment, your target size and reticle size adjust accordingly.

There are different types of reticles, from the standard crosshairs to the Ballistic Plex from Burris.


Side Focus

A side focus enables parallax adjustment. You can rotate its dials to correct distance and focus on the scope.

Some Leopold rifle scopes have a side-focus dial on the left of their turret. Long-range shooters commonly use this to eliminate parallax.


Subtension measures the surface area or the length of the two ends covered by the crosshairs on the target.

This is usually in centimeters or inches.



A trajectory is the arc-shaped flight of your bullet after it leaves the barrel of your rifle. The arc will depend on the weight of your bullet and its velocity.

Twilight Factor

This metric is used to measure the efficiency of a rifle scope under low-light circumstances.

The LARGER your objective lens and the higher your magnification, the better your twilight factor.

Determining the twilight factor involves getting the square root of the magnification multiplied by the diameter of the objective lens.

However, the twilight factor might significantly change when glass quality and coatings are considered.

Determining twilight factor is a good way to compare different optic performances under low light.

You want a scope that can still produce CRISP and CLEAR images under low light conditions.


Varmint Hunting

Hunting of varmint is the shooting of small mammals, usually for pest control.



Zeroing (also known as sighting) your scope means making sure that your bullet lands where you want it to.

In other words, it is dialing you reticle to ensure your point of aim and point of impact MATCH.

I started off zeroing my scope at 100 yards, which is a safe distance for beginners to start with. You can work your way up once you’ve gotten the hang of it.

Parts of a Rifle Scope


Now that you know all the important shooting terms, let’s take a closer look at the different parts of the scope itself.

Adjustable Objective

You can find the adjustable objective dial at the objective end of the scope, or it can also come as a knob on the left side of the turret housing.

This allows you to adjust your scope’s parallax to a certain distance to see a clearer picture of your target.

You should set the adjustable objective to the one that prevents apparent movement between the reticle and the target when you move your head a bit off-center from the rifle scope.

Airgun Scope

An airgun scope withstands the dual-recoil of spring piston airguns.

Because of the power created when an airgun is fired, scopes can be easily destroyed. Hence, airgun scopes are sealed on both sides of their lenses for added strength.

Elevation Adjustment

This dial is used to change the POI of the rifle either above or below the target.

Exit Pupil

Any optical instrument with magnification uses an exit pupil, telescopes and binoculars included!

The exit pupil controls the BRIGHTNESS of an image to be viewable by the shooter’s eye.

The larger the exit pupil, the brighter the image.

The exit pupil is a small circle of light seen through the ocular lens when the device is held at arm’s length.

To measure for exit pupil, divide the objective lens diameter in millimeters by the magnification.


It is the front end of the rifle where the projectile exits.

Objective Lens

The objective lens of a rifle scope is the most important part of the optical system. It is the lens closest to the object examined.

The larger the diameter of the objective lens, the MORE LIGHT enters, so the clearer the image. The objective lens fdiameter is measured in millimeters.

Ocular Lens

The ocular lens, on the other hand, is the lens closest to your eye.

It focuses on the image being magnified and is flipped right-side up for the eye to translate visually.

The diameter of your ocular lens also determines the amount of eye relief. It should be at a distance that allows you to comfortably focus on an image.


A turret is a knob outside the scope tube, marked with elevation and windage adjustment increments.

Windage Adjustment

Windage is how much the point of impact is to the left or right without adjusting your scope.

This lets you know how to adjust your scope according to the wind.

Frequently Asked Questions

Armed soldier looking through scope

I’ve got you covered with answers to questions hunters and rifle enthusiasts are keen to know!

How Do I Clean My Riflescope?

Cleaning your riflescopes is vital to assure your rifle’s long lifespan. Here are the steps:

  1. Clear away large particles – Start by using compressed air or a soft lens brush to brush off dirt particles from the scope.
  2. Wipe down the body – Wipe with water and a soft towel on the scope’s body. You can even use a brush to remove stubborn debris.
  3. Wipe the lenses – With a soft microfiber lens cloth, wipe the lenses in a spiral motion. You can also apply an eyeglass cleaner to help. Wait to dry.

What Do Gun Scope Numbers Mean?

The first number refers to the magnification of the rifle, while the second number refers to the diameter size.

For example, the Primary Arms 4-14×44 scope has a magnification of 4-14x and a diameter size of 44mm.

You will also see figures also measure the field of vision, eye relief, elevation & windage, MOA, MRAD, tube diameter, etc.

What Does IR Stand for on a Rifle Scope?

IR stands for Illuminated Reticle.

This option allows you to illuminate the reticle to better see your target in low light conditions.

What Are Rifle Scope Mounts?

A scope mount attaches the scope to the rifle. It comprises scope rings and a base mount to keep it in place.


Sniper aiming from the ground

There are still a ton of terms out there that will help you level up your expertise when it comes to rifle scopes.

You’re just getting started!

I hope this guide has kept you interested and seeking more experiences in this exciting hobby.

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