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joe9838
Oct 15, 20245 min read

Understanding Rifle Scopes: What the Numbers Mean and How They Affect Shooting

Updated: Nov 13, 2024


Selecting the right rifle scope can be a game-changer for hunters, target shooters, and anyone looking to improve their accuracy. One of the most important aspects of choosing a scope is understanding the numbers printed on the side, such as "3-9x35" or "4-12x50." These numbers indicate key features of the scope that directly impact your shooting experience, such as magnification and objective lens size. This guide will walk you through the meaning of these numbers and explain how they affect your shooting, helping you choose the best scope for your needs.


Magnification: The First Set of Numbers

The first set of numbers on a scope refers to its magnification power. For example, in a “3-9x35” scope, the "3-9x" means the magnification is adjustable from 3x to 9x. This allows you to zoom in on distant targets and see them more clearly.

Fixed vs. Variable Magnification

  • Fixed Power: A fixed-power scope has a single magnification level, such as "4x32." These scopes tend to be more durable and simpler to use, making them a great choice for beginners or those who do not need variable zoom.

  • Variable Power: A variable-power scope offers adjustable magnification, such as "3-9x," meaning you can zoom in from 3x to 9x. These scopes are versatile, allowing you to shoot at various distances by adjusting the magnification to fit the situation.

Impact on Shooting:

  • Lower magnification (e.g., 3x) provides a wider field of view, making it easier to track moving targets, especially at closer ranges.

  • Higher magnification (e.g., 9x) allows you to focus on distant targets with more precision but narrows your field of view.


Objective Lens Diameter: The Second Set of Numbers

The second number in the scope's description, such as the "35" in a "3-9x35" scope, refers to the diameter of the objective lens in millimeters. The objective lens is located at the end of the scope farthest from your eye and is responsible for gathering light.

How Objective Lens Size Affects Shooting:

  • Light Transmission: Larger objective lenses allow more light into the scope, which results in a brighter image, especially in low-light conditions such as dawn or dusk. A scope with a 50mm objective lens will generally provide a brighter image than one with a 32mm lens.

  • Weight and Mounting: Larger lenses also add weight to your rifle and may require higher mounting rings to fit your firearm properly. This can affect the balance of your rifle, so it’s important to choose a lens size that complements your rifle and shooting style.


Eye Relief: Comfort and Safety

Eye relief is the distance between your eye and the scope’s eyepiece at which you can see a full, clear image. Scopes with longer eye relief are particularly important for rifles with strong recoil, such as those used for big-game hunting.

How It Affects Shooting:

  • Comfort and Safety: Scopes with short eye relief (e.g., 3 inches) can cause discomfort or even injury if the rifle recoils too close to your eye. Scopes with longer eye relief (e.g., 4-5 inches) are safer and more comfortable to use with high-recoil rifles, like those chambered in .308 or .30-06.

  • Field of View: Longer eye relief tends to reduce your field of view, so balancing comfort and functionality is key.


Reticles: Crosshairs for Precision

Reticles, or crosshairs, are the aiming points you see when looking through the scope. Different reticle designs cater to different shooting needs.

Common Types of Reticles:

  • Duplex Reticle: The most common type, featuring thick outer lines that taper to thin crosshairs in the center. Ideal for hunting and general shooting.

  • Mil-Dot Reticle: Includes dots along the reticle lines for estimating range and adjusting for windage and bullet drop. Common among long-range shooters.

  • BDC (Bullet Drop Compensation) Reticle: Designed with marks or dots that correspond to specific distances, allowing for quick adjustments when shooting at varying ranges.

How Reticles Affect Shooting:

  • Simple reticles like the duplex are ideal for fast target acquisition and hunting.

  • Complex reticles like the Mil-Dot or BDC are better for long-range precision shooting, as they allow you to account for bullet drop and wind.


Parallax Adjustment: Fine-Tuning for Accuracy

Parallax occurs when the target and the reticle are not in the same focal plane, which can cause the reticle to appear as if it’s moving off the target when you move your head. Many scopes include parallax adjustment to correct this, especially at higher magnifications.

How Parallax Affects Shooting:

  • At lower magnifications (under 10x), parallax is not a significant concern, and most scopes are set to be parallax-free at 100 yards.

  • At higher magnifications, parallax can affect accuracy, particularly for long-range shooting. Adjustable objective (AO) scopes or side focus knobs allow you to fine-tune the parallax and maintain accuracy at varying distances.


Scope Coatings: Enhancing Light Transmission

Modern scopes often come with special coatings on the lenses to improve light transmission and reduce glare. There are four levels of lens coatings:

  • Coated: A single layer of coating on one lens surface.

  • Fully Coated: A single layer of coating on all external glass surfaces.

  • Multicoated: Multiple layers of coating on at least one lens surface.

  • Fully Multicoated: Multiple layers of coating on all external glass surfaces.

Impact on Shooting: Fully multicoated lenses offer the best light transmission and glare reduction, providing a clearer and brighter image in various lighting conditions.


First Focal Plane (FFP) vs. Second Focal Plane (SFP)

When it comes to variable-power scopes, the placement of the reticle can either be in the first focal plane (FFP) or the second focal plane (SFP).

  • First Focal Plane (FFP): The reticle changes size as you adjust the magnification, making range estimations consistent at any magnification level. Ideal for long-range shooters who need to make quick adjustments.

  • Second Focal Plane (SFP): The reticle remains the same size regardless of magnification. This is common in hunting scopes where quick target acquisition at varying ranges is needed.

How FFP and SFP Affect Shooting:

  • FFP is better for long-range precision shooting where accuracy at varying magnifications is critical.

  • SFP is typically preferred for hunting and general shooting where the reticle size remaining constant is more user-friendly.


Understanding the numbers and features of a rifle scope is key to choosing one that fits your shooting style and needs. Whether you're after high-magnification precision for long-range shots or a durable, multi-purpose scope for hunting, knowing how to interpret scope specifications will help you make the right decision.


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