Firearms Glossary: What are MOA, FOV, POI and more?

Firearms Glossary: What are MOA, FOV, POI and more?

By Sightmark  

Have you ever found yourself sitting around the campfire, at the gun range, or out in the field confused about the conversation? Then you probably need to read this.

This is firearm verbiage for beginners.

We can certainly understand why someone would be lost when hearing acronyms like FOV, POI, and MOA. Even someone who has been around firearms and the outdoors their whole life can find themselves tongue-tied when these terms come up. Here, Sightmark has simplified some of the most common terms any hunter, long-range shooter and firearm owner should recognize and comprehend.

Let’s start with what’s already been mentioned: FOV, POI and MOA.

Field of View (FOV)

The field of view is the observable area that a human can view through an optic device.

For example, when you look through a scope, any kind of scope, the area that is confined to what you are actually observing through the end of that scope is your field of view or FOV. The FOV can be measured in degrees or linear field.

 

Point of Impact (POI)

The POI shows the relationship between where you are aiming and where the bullet is going to hit.


The point of impact is where the bullet or laser hits the target. This is where the most impact will be had by pulling the trigger to fire or by aiming the laser downrange. This is especially useful for shotgun operators since a shotgun is designed to project a scattered pattern rather than a single shot.

Your POI also shows a relationship between where you are aiming and where the bullet is going to hit. This can tell a rifle operator how far off their gun is from accurately being sighted in.

Minute of Angle (MOA)

You will hear this term most in long-range shooting. Minute of angle is often used to describe the size of the target. 1 MOA on a target that is 500 yards away is 5.”

But let’s say the MOA on this target is actually 2. This means the target is 10″ in diameter. However, how much 1 MOA affects your POI, depends on the distance of the target.

For example, there is a target sitting at 100 yards. An adjustment of 1 MOA on that target will move your POI 1.” This directly correlates in much higher distances as well. Let’s say there is a target at 1,000 yards. 1 MOA adjustment will now move this POI 10.”

This helps shooters to more accurately hit their mark when shooting long-range because the bullet drops after firing due to factors such as wind, upwards or downwards angles, and gravity.

Now that we’ve tackled these 3 basic terms, let’s delve a little deeper!

Objective Lens

The objective lens is the lens at the end of the scope. This diagram is also invaluable for anyone confused about the location of various riflescope components.

 

This is the lens at the end of the scope. Not the lens that you look through, but the lens on the other end of the optic. For example, anytime you see 1-9×30, this means that scope can magnify from 1 to 9 and the diameter of the objective lens is 30 millimeters.

Reticle


Sightmark reticle example.

A reticle is anything in the scope that helps you aim. In its simplest form, a crosshair is a reticle. A reticle can be etched onto the glass. This allows for the reticle to change in size as the scope magnifies (something also known as first focal plane) or to change color based on user preference.

A reticle can also be fixed by being made from wire. You can tell whether a reticle is fixed or not by looking through the scope—if the crosshair is fixed at each edge of the scope, it is most likely not etched onto the glass lens.

Eye Relief

The eye relief is the distance between the eyepiece of the scope and your eye where you can see the full field of view.

This is the distance between the eyepiece of the scope and where the eye sees the full FOV with no dark edge around the image. If you are looking through a scope and there is a dark circle around the image, scoot your head closer to the sight.

If you look through a scope and can’t see any dark edges, move your head back a little. Find that sweet spot where you can rest your cheek comfortably against the stock of the gun and see through the scope without any dark edges, but if you moved even a centimeter forwards, you would see a black circle distorting your FOV. If you take anything away from this article, I would suggest this be it.

The repercussions of not allowing yourself enough eye relief can lead to something called “scope eye” or “scope bite.” This is when a shooter is too close to the end of a scope and the gun’s recoil causes the scope to hit the shooter and slices their eyebrow open and/or gives them a black eye.

Second Focal Plane

 


The Citadel LR2’s first focal plane reticle.

As mentioned earlier, the first focal plane is when the reticle gets bigger as the operator zooms in, and gets smaller as the operator zooms out. The reticle adjusts in size as the scope magnifies. A second focal plane is the opposite of this—the reticle is fixed in size no matter how magnified the scope can be.

Ballistics

Ballistics is the study of projectile motion and effects. In the case of guns, it refers to all factors that affect the bullet, including the velocity, trajectory, size of load, rifling, and more.

Each weapon has its own unique “ballistic signature,” which leaves markings on the bullets. This allows police laboratories to determine whether two bullets were fired from the same weapon.

Action

A firearm’s working mechanism (typically the receiver or frame and breech bolt) that facilitates its firing and loading/unloading. There are a variety of types of actions from single to automatic.

Magazine

Refers to either a permanent or detachable, spring-loaded container for cartridges. It is often considered the same as a clip.

One distinction is that, externally, a magazine appears to complete the firearm’s form, while a clip is an ammunition insert (or transfer device) that does not affect external appearance.

Some Takeaways

Firearm terminology is expansive, fluid and sometimes all-too-technical. No one knows everything. If you’re interested in understand the terminology behind calibers, you can check out this blog.

It’s always beneficial to learn new things. Here at Sightmark, we’re interested in educating our customers about firearms terminology, safety, laws, and best practices, in addition to providing our loyal customers with top-notch red dots, night vision and other optics.

We hope the understanding of these common terms help you get involved in the conversation and also helps you understand how your firearm can work better for you!

What riflescope or optics terms do you not fully understand? Leave your questions in the comment section and we will do our best to answer them!