If you’re new to rifles or optics, you might wonder what the numbers on rifle scopes mean. These figures are the key to understanding a scope’s magnification and light-gathering ability, and they directly affect your accuracy. Let’s break down the common formats so you can choose the right tool for your shooting.
What Do The Numbers On Rifle Scopes Mean
At its core, the numbers on a scope describe its magnification power and the size of its objective lens. They are usually presented in a format like “3-9×40” or “4×32.” Reading these numbers correctly is the first step to using your scope effectively.
The Basic Number Format Explained
The most common designation you’ll see is something like “3-9×40.” This string of numbers tells you three critical things.
- First Number (Magnification Range): The “3-9” part. This means the scope offers variable magnification, from 3 power (3x) up to 9 power (9x). At 3x, the target appears three times closer than it does with your naked eye.
- The “x”: This simply means “by” or “times.” It seperates the magnification number from the objective lens diameter.
- Last Number (Objective Lens Diameter): The “40” in our example. This is the diameter of the front lens in millimeters. A larger lens generally gathers more light, providing a brighter image.
Fixed Power vs. Variable Power Scopes
Scopes come in two main types: fixed and variable power. The numbers make this distinction clear.
- Fixed Power (e.g., 4×32): These scopes have one set magnification. The “4x” means it magnifies the image four times. They are simple, durable, and often more affordable.
- Variable Power (e.g., 3-9×40, 5-25×56): These scopes offer a range. A 5-25×56 scope can adjust from 5x to 25x magnification. This versatility is great for hunting where shot distances can change quickly.
Understanding Objective Lens Size
The second number, like the “40” in 3-9×40, is the objective lens diameter in millimeters. This matters for two reasons.
- Light Transmission: A bigger lens (e.g., 50mm) captures more light than a smaller one (e.g., 28mm). This results in a brighter sight picture, which is crucial during dawn, dusk, or in heavy cover.
- Size & Weight Trade-off: Larger objective lenses mean a heavier and bulkier scope. They also need to be mounted higher on the rifle to clear the barrel, which can affect cheek weld.
What About Other Numbers on the Scope?
Beyond the main model designation, you’ll see other numbers on the adjustment turrets and the reticle.
- Adjustment Turret Numbers: These are marked in MOA (Minute of Angle) or MRAD (Milliradian). They tell you how much the point of impact will move per click. For example, “1/4 MOA” means each click moves the impact 1/4 inch at 100 yards.
- Reticle Numbers: Some reticles have markings for holdover or windage. These numbers help you aim without adjusting the turrets, using subtensions in MOA or MRAD.
How to Choose the Right Scope Numbers for You
Picking a scope isn’t about getting the biggest numbers. It’s about matching the numbers to your specific use. Here’s a simple guide.
- Consider Your Typical Shooting Distance:
- Close-Range (under 100 yards): Low magnification like 1-4x or 2-7x is ideal for fast target acquisition.
- Medium-Range (100-300 yards): A versatile 3-9x or 4-12x scope is the most popular choice.
- Long-Range (300+ yards): You’ll want higher magnification, like 5-25x or 6-24x, to see distant targets clearly.
- Think About Your Game and Environment:
- Hunting in thick woods? A low-power, wide-field scope (like 1-6x) is better.
- Target shooting on an open range? Higher magnification and a larger objective lens (like 10-50×60) help with precision.
- Don’t Forget About Eye Relief: This number, listed in the manual (e.g., 3.5 inches), is the distance your eye must be from the ocular lens for a full view. It’s critical for safety with high-recoil rifles.
Common Mistakes to Avoid
When interpreting scope numbers, a few pitfalls can lead to a poor choice.
- Over-Magnifying: More power isn’t always better. High magnification narrows your field of view, amplifies shake, and can make finding a target slow. For most big-game hunting, you rarely need more than 10x.
- Ignoring the Exit Pupil: You can calculate this by dividing the objective lens diameter by the magnification. For example, at 9x on a 40mm scope, the exit pupil is about 4.4mm. In low light, you want this number to be close to the 7mm diameter of your dilated pupil.
- Choosing a Huge Objective for a Lightweight Rifle: Putting a massive 56mm scope on a mountain rifle defeats the purpose of a light carry. Balance is key.
Putting It All Together: A Practical Example
Let’s say you see a scope labeled “2-10×42.” Here’s exactly what that means:
- It’s a variable power scope.
- You can adjust it from 2x magnification (wide view for close shots) up to 10x magnification (for more precise, farther shots).
- The front lens is 42mm in diameter, offering good light gathering for dawn or dusk hunting.
- This scope would be an excellent, versatile choice for a deer hunter who might encounter shots from 50 to 300 yards.
FAQ Section
What does 4×32 mean on a rifle scope?
It means a fixed 4x magnification with a 32mm objective lens. It’s a common, simple setup for .22 rifles or close-range shooting.
What is a good scope magnification for 100 yards?
For target shooting, 10x or 12x is great for seeing small bullseyes. For hunting at that range, 4x to 6x is often plenty, allowing for a quicker shot.
Is a 50mm objective lens better than a 40mm?
A 50mm lens gathers more light, which can mean a slightly brighter image in very low light. However, it makes the scope heavier and taller. For most situations, a 40mm or 44mm lens offers a great balance of performance and size.
What does “MOA” mean on my scope’s adjustment dial?
MOA stands for Minute of Angle. A “1/4 MOA” click will move the point of impact approximately 1/4 inch at 100 yards, 1/2 inch at 200 yards, and so on. It’s a angular measurement used for adjustments.
Can I use a high magnification scope for short range?
You can, but it’s not ideal. At high power, your field of view is very narrow, making it hard to locate a fast-moving or close target. It’s like looking through a straw. Lower power is much faster for short-range work.
Understanding what the numbers on rifle scopes mean empowers you to make a smart purchase. Remember to match the magnification range and objective lens size to the type of shooting you actually do. With this knowledge, you can look past the marketing and select a scope that truly fits your rifle and your needs, making your time at the range or in the field more succesful.