If you’re new to rifles or optics, figuring out how to read rifle scope numbers can feel confusing. These numbers on your scope aren’t random—they’re the key to understanding its power and field of view. This guide will break down what those markings mean in simple terms, so you can choose and use your scope with confidence.
How To Read Rifle Scope Numbers
You’ll find the main numbers etched or printed on the scope’s main tube, usually on the eyepiece or magnification ring. A common example is “3-9×40.” Let’s take that apart piece by piece. The first number, or set of numbers, refers to the magnification. The number after the “x” is the objective lens diameter. Understanding this is your first step to mastering your optic.
Breaking Down the Magnification Number
The magnification number tells you how much closer the target will appear compared to the naked eye. In our “3-9×40” example, the “3-9x” part is the magnification range.
- 3x: This is the lowest setting. At 3x, the target looks three times closer than it does with your eye alone. It’s great for wider fields of view and closer shots.
- 9x: This is the highest setting. At 9x, the target appears nine times closer. You use this for precise aiming at longer distances.
- The Dash (-): The dash indicates it’s a variable-power scope. You can adjust the magnification anywhere between 3 and 9 times.
Some scopes have fixed power, like “4×32.” This means it’s stuck at 4x magnification and cannot be adjusted. Variable scopes offer more flexibility for different shooting situations.
Understanding the Objective Lens Size
The second main number is the objective lens diameter, measured in millimeters. In “3-9×40,” the “40” is the lens size. This lens is at the front of the scope, farthest from your eye.
- A larger lens (like 40mm, 44mm, or 50mm) gathers more light. This gives you a brighter image, especially in low-light conditions at dawn or dusk.
- A smaller lens (like 28mm or 32mm) keeps the scope more compact and lightweight. It might sit lower on your rifle.
There’s a trade-off. Bigger lenses offer better light but can make the scope heavier and require higher mounting rings.
Other Important Numbers and Markings
Scopes often have other specifications listed. Don’t overlook these, as they are crucial for performance.
Field of View (FOV)
Often listed in feet at 100 yards, this tells you how wide an area you can see through the scope at a set distance. A wider FOV (e.g., 30 ft at 100 yds) lets you see more area, which is helpful for tracking moving targets. Higher magnification usually narrows the FOV.
Eye Relief
This is the distance your eye must be from the eyepiece to see the full picture. It’s critical for safety, especially on high-recoil rifles. A longer eye relief (3.5 to 4 inches) is safer and more comfortable. If your scope is to close, you might get hit by the eyepiece during recoil.
Adjustment Turrets and Click Values
The turrets are the knobs on top and side of the scope. They are usually marked with directions like “Up” and “R” for right. The most important marking is the click value, such as “1/4 MOA.” This means each audible “click” when you turn the knob will move the point of impact by 1/4 Minute of Angle at 100 yards. Knowing this is essential for accurate sighting-in.
How to Choose a Scope Based on the Numbers
Now that you can read the numbers, how do you pick the right one? It depends on what you’re using the rifle for.
- Brush Hunting (Deer in woods): A lower magnification like 1-4x or 2-7x is ideal. You need a wide field of view for quick shots at closer ranges.
- Long-Range Varmint or Target Shooting: You’ll want higher magnification. A scope like 4-16x or 6-24x helps you see small targets far away clearly.
- All-Around Big Game Hunting: A classic 3-9×40 or 4-12×40 is a very popular and versatile choice for many hunters. It offers a good balance for various shot distances.
Remember to match the objective lens size to your needs. If you often shoot in low light, prioritize a larger objective lens (like 44mm or 50mm). For a light, handy rifle, a 32mm or 40mm might be perfect.
Putting It All Together: A Step-by-Step Example
Let’s say you pick up a scope marked “4-16×50 SF FFP 30/30.” Here’s how to read it:
- 4-16x: Variable magnification from 4x to 16x.
- 50: A 50mm diameter objective lens for good light gathering.
- SF: Likely stands for Side Focus, a parallax adjustment knob on the side.
- FFP: First Focal Plane. This means the reticle grows and shrinks with magnification, keeping holdover points accurate at all zoom levels.
- 30/30: Probably indicates it has 30mm main tube diameter and 30mm of adjustment per revolution in the turrets, though this can vary by brand.
By understanding each part, you can quickly gauge the scopes capabilities and intended use—in this case, a scope built for precise, long-range shooting.
Common Mistakes to Avoid
When learning how to read rifle scope numbers, a few common errors can lead to the wrong choice.
- Over-magnifying: More power isn’t always better. High magnification amplifies shaky hands and narrows your field of view dramatically. Choose a range suitable for your typical shooting distance.
- Ignoring Eye Relief: For a high-recoil rifle like a .300 Win Mag, a scope with short eye relief is a bad idea. Always check this spec for safety and comfort.
- Forgetting About Mounting: A 50mm objective lens might need extra-high rings to clear the rifle barrel, which can effect your cheek weld. Make sure your setup accommodates the scopes physical size.
Taking a moment to consider these factors will save you frustration later. Its worth planning your entire setup before you buy.
FAQ Section
What does 3 9×40 mean on a scope?
It means the scope has variable magnification from 3 power to 9 power, and it has a 40mm diameter objective lens. It’s a very common configuration for hunting rifles.
What is the best scope magnification for 100 yards?
For target shooting at 100 yards, a fixed 10x or a variable like 4-12x works very well. For hunting at that distance, a lower power like 3-9x or 4x is often sufficient and offers a wider view.
Are bigger rifle scopes better?
Not necessarily. Bigger scopes with large lenses gather more light but are heavier and bulkier. The “best” scope is the one that matches your rifle’s purpose and your personal preferences for weight and size.
What does MOA mean on a scope?
MOA stands for Minute of Angle. It’s a unit of measurement for the adjustment turrets. A common value is 1/4 MOA per click, meaning each click moves the bullet’s point of impact by about 1/4 inch at 100 yards (roughly 1 inch at 400 yards).
Learning how to read rifle scope numbers demystifies your optic and makes you a more informed shooter. Start by identifying the magnification and objective lens size on your own scope. Then, look for the other markings like FOV and eye relief. With this knowledge, you can make smarter purchases, set up your gear correctly, and ultimately shoot with greater precision and confidence. Remember, the right scope, understood properly, is a powerful tool in your shooting toolkit.