When it comes to choosing a rifle scope, the numbers can be a bit confusing for beginners. What do those numbers actually mean and how do they affect your shooting experience? Let's dive into what those numbers actually mean.
Magnification Power
3-9X40
The first set of numbers on a rifle scope typically represent the magnification power. The first number 3 means the minimum magnification level that the scope offers. Second number 9 the maximum magnification level. Because the first 2 numbers are a range separated by a hyphen we know this is a zoom scope, the magnification can be adjusted from 3 times to 9 times closer than the naked eye. .
The numbers before the X always denote magnification power or power range and the numbers after the X denote the size of the objective lens in mm.
Here's another example listing that looks slightly different:
4X32First number before the X means 4X magnification power or '4 power' for short and the 32 means a 32mm objective lens. This scope is fixed, you can't alter the magnification by zooming in or out. We know because the first number doesn't specify a range.Sometimes you may see listings or specifications like this:
6X scope or 8X scopeThe above is just shorthand for magnification power. 6X means 6 times magnification or '6 power'. This would be a fixed magnification scope. 6X is an image that's 6 times bigger than what you see with the naked eye. Here's an example of the effects of 6X magnification levels on an object.
Objective Lens Sizes
The second number in the sequence, in this case "40" in "3-9x40", refers to the diameter of the objective lens in millimeters. A larger objective lens allows more light to enter the scope, resulting in a brighter image. This is particularly useful in in low light conditions like dusk.
Medium Objective Lens Size (30-44mm)
Medium Objective Lens size is usually between 40mm and 44mm in diameter. These are the most common objective lens sizes available in the market, with several options including the 3-9x32, 3-9x40, 3-12x40，4-14x44. it's compact while not being too small, not too large, offers a balance between light transmission and overall scope size. It provides adequate light gathering capability, without adding excessive weight or bulk to the rifle. When mounted sits nice and snug atop the barrel.
Large Objective Lens Size (>50mm)
A larger objective lens allows more light to enter the scope, resulting in a brighter image. This can be particularly beneficial in extreme shooting situations , such as dawn or dusk, night vision or low light shooting, and backcountry hunting, where visibility is limited. The increased light transmission can enhance clarity and detail, making it easier to acquire your target.
The only downsides come when paired with your rifle, in that they can be on the bulkier and top heavy side and may be impractical to carry around on long distances. Additionally, a larger objective lens may require higher mounting rings to accommodate the size, which can impact the overall balance of your rifle.
What Objective Lens Size is Right for You?
Choosing the right objective lens size depends on your shooting needs and preferences. If you frequently shoot in low-light conditions or require maximum clarity, a larger objective lens, such as 50mm or even 56mm, may be the best choice. However, if you prioritize a lightweight and compact setup, a smaller objective lens, like 40mm or 44mm, may be more suitable.
Exit Pupil Size
Exit pupil size refers to the diameter of the beam of light that exits the eyepiece of an optical device, such as a telescope or binoculars. The exit pupil size is calculated by dividing the objective lens diameter by the magnification. A larger exit pupil size means a brighter image, especially in low-light conditions. For example, a 8x40 scope will have an exit pupil size of 4mm.
While the diameter of lens is a fixed measure, the variable magnification means that there are minimal and maximal exit pupil values. With a 2-16×50 rifle scope, where the power of magnification setting can be adjusted anywhere from 2 to 16, the smallest exit pupil is set at 3.125 mm and the biggest one possible at 25mm. but such a big diameter would not have any advantage (because the human eye pupil is maximal 8 mm big), the manufacturers install an optical insert which doesn't let the exit pupil diameter grow too big at small magnifications.
Field of View
Field of View, often abbreviated as FOV, it is the area that can be seen through the scope at a specific distance, typically measured in degrees and can vary depending on the specific device being used. Maximal field of view is the range of your visual area, for riflescopes its measured at 100m. For example, if a maximal field of view is 13m/100m, means that you have on 100m a maximal view of 13m. Riflescopes with variable magnification, the maximal field of view is meant when using the lowest magnification setting. The higher the magnification the smaller the field of view.
Field of view is an important feature when choosing a riflescope for your activity. A larger field of view will give you a wider view/image, which is an important factor when you are aiming or hunting moving targets. Opposite, smaller field of view gives you narrower view/image, this option is more suitable for non-moving/static targets.
Adjustment Turrets
Rifle scopes often come with adjustment turrets for windage and elevation. Jutting out from the scope body, they are exposed and easily accessible, allowing you to adjust while aiming. These turrets allow you to make precise adjustments to compensate for bullet drop and wind drift. Each click of the turret represents a specific measurement, such as 1/4 MOA (Minute of Angle) or 1/10 MIL (Milliradian).
The main categories are: Capped/Hunting turrets, Target turrets which are also capped but much higher, BDC turrets (Bullet Drop Compensation turret) and Tactical turrets.
