When you're looking at a rifle scope, you'll often see a series of numbers printed on the turret, the side, or the scope's description. These numbers provide critical information about the scope's magnification power, field of view, adjustments, and more.
Understanding these numbers on reflex sight will help you choose the right scope for your needs, whether you're hunting, shooting long-range, or using it for tactical purposes.
Here's a breakdown of the most common numbers you’ll encounter:
1. Magnification Numbers
The first set of numbers on a rifle scope typically represents the magnification power of the scope. For example, in a scope marked "3-9x40," the "3-9" refers to the zoom range.
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"3-9": The scope can magnify from 3x to 9x. The first number (3x) indicates the lowest magnification, and the second number (9x) shows the highest magnification. The "x" means "times" or "multiplied by," so a 9x magnification means the target appears nine times closer than it would with the naked eye.
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Variable Magnification: This means you can adjust the magnification within the stated range, allowing flexibility depending on your shooting conditions or target distance.
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Fixed Magnification: In some cases, scopes may have a single, fixed magnification, such as "4x" or "10x." This means you cannot zoom in or out.
2. Objective Lens Diameter
The next number you’ll usually see is the size of the objective lens, which is the front lens of the scope. In the "3-9x40" example, the "40" represents the diameter of the objective lens in millimeters.
- Objective Lens Size: A larger objective lens gathers more light, which helps create a brighter image, especially in low-light conditions like early morning or evening hunts. However, larger objective lenses may add weight to the scope and increase the overall size, which can be cumbersome for some users.
3. Exit Pupil
The exit pupil is an important measurement for understanding how much light exits the scope and reaches your eye. It’s typically shown as the ratio of the objective lens diameter to the magnification power.
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How to Calculate Exit Pupil: Divide the objective lens diameter by the magnification power. For example, a 3-9x40 scope has an exit pupil of 40 ÷ 9 = 4.44 mm.
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Why It Matters: A larger exit pupil is beneficial for low-light situations, as it ensures more light reaches your eye, making it easier to see your target in dim conditions. For example, scopes with exit pupils of 4mm or larger are often preferred for hunting at dawn or dusk.
4. Field of View (FOV)
The field of view refers to how much of the landscape you can see through your scope at a given distance. It is often stated in terms like "10 feet at 100 yards" or "30 feet at 100 yards."
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How It Works: A larger field of view allows you to see a wider area, which is helpful when tracking moving targets or aiming at fast-moving game. However, higher magnification scopes often have a narrower field of view.
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Trade-Off: While a higher magnification zooms in on distant targets, it reduces the FOV, which can make it harder to track the target.
5. Adjustment Dial Numbers
Most rifle scopes come with adjustment dials that allow you to zero in on your target. These dials adjust both elevation (up/down) and windage (left/right) settings.
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MOA (Minute of Angle): One of the most common adjustments is in MOA (minute of angle), which translates to about 1.047 inches of movement at 100 yards. For instance, if a scope has "1/4 MOA" adjustments, each click of the turret moves the reticle 1/4 inch at 100 yards.
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MIL (Milliradian): Another common system is the MIL system, where each click moves the reticle by 1/10th of a mil. It’s more precise than MOA and is often used in military or tactical settings.
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Adjustment Range: The total range of adjustments, which is the maximum distance the scope can adjust for elevation or windage, is usually listed as a range (e.g., "100 MOA" for windage and "80 MOA" for elevation).
6. Parallax Adjustment
Some rifle scopes also include a parallax adjustment, which helps eliminate the parallax error (when the reticle appears to move relative to the target). This adjustment is typically found in scopes used for long-range shooting.
- Parallax-Free: Many modern scopes are parallax-free at 100 yards, meaning that the reticle will not shift as you move your head or eye. However, for longer distances, you'll need to adjust the parallax to match the distance to your target.
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