How to Choose a Rifle Scope

If you have been looking for a new scope for your rifle, you may already be bewildered by all of the different options on the market. What do these specs even mean?

These concepts get technical and complicated fast. The gun enthusiast at the range will gladly give you an hour and a half of his time to talk your ear off about reticles.

Or, learn the basics here in ten minutes. Your call.

Scopes come with some fairly standard kinds of features and specs that you should understand in order to make a purchase that fits your specific needs. Below I have covered the basics to help you make an informed rifle scope purchase.

What to Look For

Reticle (a.k.a. crosshairs)

Fancy word, simple concept. There are lots of different styles of reticles to choose from, with different shooters learning over time what works best for them.

If you are doing largely midrange targeting in low to moderate light with busy fields of vision (like hunting in the woods), then thicker reticles are an advantage, even though they sacrifice a small amount of precision. Simply put, thicker reticles are just easier to see.

If precision is your first priority, for example in competition shooting, then a finer reticle may be in order.

The plain plus sign shaped reticle is called a “duplex reticle” and it is the most common type. Most hunters find this perfectly adequate.

If a reticle has Mildots on it, you can use this to estimate the distance to target, potentially helpful in working out windage and elevation adjustments for long range shooting. It is the reticle of choice for most military and police snipers.

BDC, or “Bullet Drop Compensator” scopes, have horizontal lines that allow you to adjust for the bullet drop over distance. They are most helpful if you are range shooting and switching between long and short range targets without time to adjust knobs for elevation. BDCs are only reliable if they are properly calibrated to the specific weapon.

Fixed verses variable scopes

The difference here is that fixed scopes come set at a certain magnification, and variable scopes come with a range of magnification settings that you can adjust between. Fixed scopes are generally cheaper, and variable scopes get more expensive with wider ranges, and higher maximum magnification.

4x is a pretty popular scope magnification for hunters. Much more than that starts to be paying for scope you are not going to use. Remember, you want to use the least amount of magnification to give you a clear shot of your target, for both accuracy and control over the reticle.

Objective Lens Diameter (OLD)

This number can be found after the “x” in the primary specs for the scope and it refers to the diameter of glass at the end of the tube closest to your target, in millimeters. And OLD of 30 is standard. A larger OLD becomes more critical for longer zooms, particularly over 10X.

If you already decided a 4x magnification is all you need, then anything over 30 OLD is a waste.

Adjustment systems: MOA verses MRAD

Scopes need to be adjusted for the weapon, the shooter, and conditions. There are two systems to choose from.

  • MOA (Minute of Angle)

The MOA system is more common and more or less corresponds to a 1 inch adjustment at 100 yards per “click.”

The main upshot of the MOA system is that it has pretty fine increments of change, allowing for really precise zeroing even at longer ranges.

The main downside is that it is calibrated at 100 yards, so estimating changes for significantly longer or shorter ranges can be a guessing game.

  • MRAD (milradian)

The MRAD system is only paired with a mildot reticle because it calibrates precisely to the distance between center of the reticle and the bullet in mils, again at 100 yards.

You’re already looking through the scope, your bullet is 1 mil off target (because your mildots indicate this) then you adjust one mil.

Like the MOA system, you have to do some estimating as soon as you are off 100 yards, made a little easier by the fact that the MRAD system is a relative (rather than absolute) calculation. Part of the work in calculating adjustments is done for you.


Parallax is a concept that requires some technical knowledge in optics to fully understand, and, unless you want to have that hour-long conversation with diagrams and a quiz at the end, it might not even be worth getting into it.

Parallax is not a significant factor for accuracy until you are starting to get into higher magnification scopes, 12x or over. If you have already decided this level of magnification is beyond your needs, then odds are you don’t even have to think about parallax.

More good news: Most lower magnification scopes are “parallax free,” which means: You don’t need to think about parallax.

If you are still thinking about parallax…

It is useful to be able to adjust for situations over long distances with high magnification where the intersection of the focal lines is offset from the reticle, on other words, when the reticle and the target are on different focal planes.

When a rifle scope has parallax, it means that the reticle will shift slightly with small head movements from breathing or shifting positions. It can be disorienting and it adds an unnecessary challenge to siting in. This is completely unnecessary for most hunters and many competition shooters since the parallax effect is negligible at under 200 yards and 12x magnification.

If you still think parallax sounds neat, go to a gun shop and try out a scope with parallax before you spend money on one. They definitely take some getting used to.

Other features to consider

Fog-proof: Standard for most scopes but not all. If you are hunting or competing in a variety of whether conditions, this is a must.

Eye-relief: This number refers to the optimal distance from the scope to the shooter’s eye. For many rifle scopes a 4” eye relief is standard. Hand guns and high-powered rifles with hard recoil require longer eye-reliefs. If you regularly get a black eye from your gun’s recoil, then you may need a scope with a longer eye-relief.

Light transmission: This is one of those features that gets expensive fast, and you need to think about how much it will affect your standard conditions of use. Longer range shooting and higher magnification is where light transmission really comes into play. 90% light transmission is standard and plenty for most midrange shooting and most hunting applications. 98% is as high as it gets, and expect to pay a fortune for it.


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