What You Need to Know About Rifle Scope Objective Lens Diameter

How important is the rifle scope objective lens diameter? Read on to learn more about the objective lens diameter and how it affects your rifle scope.

When you are choosing a new rifle scope, you have to consider many things before you make your choice. You need to make sure that you are getting a durable and rugged scope that is built to last, one that has a quality turret system, and that has excellent optics. You will also likely want to know about the rifle scope objective lens diameter.

The objective lens diameter is often one of the first things that people look at when they are considering a new scope for their rifle. People want to know the overall size of the objective lens, and they want to know just how important it might be when they are hunting.

Below, we will be taking a closer look at rifle scope lens diameter to get a better understanding of what it is, why it can be important, and what diameter you might need. We will also be discussing two quality rifle scopes that might work well for your next scope.

Where is the Objective Lens Located on a Scope?

The objective lens is the lens that is furthest from your eye when you are looking through a scope. The objective lens is housed in the objective bell, which is simply a term used for this part of the housing.

The ocular lens is the lens through which you are looking. The scope features an erector tube, which is the body of the scope and which houses the reticle. Scopes will also have a turret system that includes adjustment knobs for elevation and windage, while some also have a side knob for parallax adjustment.

What Do the Numbers Mean When Looking at Scopes?

When you see scopes on the market, you will notice that they typically have a set of numbers associated with them. For example, you might be comparing two scopes. One is 3-9×40 and another might be 10-60×52. The first set of numbers refers to the magnification of the scope.

A 3x to 9x scope will have a variable magnification from 3x to 9x the power of the naked eye. It’s the second number that that provides you with the objective lens diameter. This would be 40 or 52 in the examples above. It refers to the size in millimeters. The objective lens is larger than the rest of the scope in most cases.

They are larger to allow more outside light to pass into the scope, which can produce a brighter image for you in the sight picture. One of the myths that you want to have dispelled now is that having a larger objective lens does not mean that you will have a wider field of view.

Factors to Consider When Choosing an Objective Lens

While it might seem like you would want to have the largest diameter objective lens for your scope to ensure you are getting the most amount of light possible, that’s not necessarily the case. You will want to consider several factors when you are choosing the diameter of your objective lens for many reasons.

Mounting the Scope

One of the first things you will want to consider is how you are mounting the scope. When you have an extremely large diameter objective lens, it could interfere with how you are mounting the scope on your rifle. Depending on the rifle and how you are mounting the scope, it can cause interference.

Keep in mind that the bell that houses the objective lens will have a larger diameter than the actual lens. This might mean you need to provide more clearance for the scope on your rifle, which means using higher mounting rings. This will keep the bell away from the barrel of your rifle. However, it could also make the rifle less comfortable to shoot and it can compromise your eye alignment.

Typically, hunters and shooters will do fine with a 50 mm objective lens. It can provide plenty of light, but it is still small enough that it will not interfere with your shooting position or your eye alignment.

How Much the Scope Weighs

The weight of the scope is something else that you will want to consider. If you are going to be carrying your rifle all day through the woods, or you will be firing multiple shots at the range, even a bit of added weight will be noticeable over time.

50 mm scopes will generally be heavier than 42 mm lenses, for example. However, even with the 50 mm lens, it shouldn’t add too much weight to the overall gear that you have to carry with you. Heavier lenses might be more than some want to carry, but they shouldn’t be more than a couple of pounds at most.

They should still be comfortable for most shooters. However, if you are the type that wants to keep the weight you are carrying as low as possible while you are hunting, this is a factor you will want to keep in mind.

The Quality of the Glass

The diameter of the objective lens won’t matter if you are choosing a scope that doesn’t provide quality glass. Most people are looking for larger objective lenses because they want to have a brighter image through their sight picture, but the diameter of the lens is only part of that equation. High-quality glass is also essential.

When you are choosing a rifle scope, always look at the quality of the glass that’s included. Many cheap rifle scopes, even those that have a large diameter, will have poor glass, which means a poor image. Look for scopes that have coatings on them that will help with the light transmission and that will help to reduce glare.

Never sacrifice clarity and quality of glass just to get a larger diameter objective lens.

How, Where, and When You Are Shooting

How far away are you going to be when you are taking most of your shots? If you are often shooting at long range, whether you are at the range or you are out hunting, then a larger diameter objective lens will make more sense, as well as higher magnification.

However, if you have shots that are at a closer range, then you might want to choose an option that has a smaller diameter lens. Remember, if you have high-quality glass, you can still get good light transmission out of a scope that has less than a 50 mm objective lens.

If you are often shooting at dusk or dawn, when there is less light, then you will find that a larger objective lens can provide you with the light that you need. If you are going to be taking shots where you need greater magnification, a large diameter objective lens works well.

What Diameter Lens Might be Right for You?

Now that you have a better idea of what the objective lens size means and how it can affect a scope, it’s time to think about the size that’s right for you. While it will often come down to how you are shooting and your preference, we’ve included some handy information that can help you make your decision.

Objective Lenses 28mm or Below

Those who are looking for a relatively low-powered scope will find that an objective lens of this size features a low profile, which can make it easier to mount. It also is light and because it is smaller, it tends to be affordable. However, they can only be used for close-range hunting.

Scopes with lenses of this size are typically used on .22 rimfire rifles or even air guns, as they are not typically able to handle the recoil from larger rounds.

Objective Lenses 30 mm to 44 mm

These will still have a low-profile mount, they are comfortable to use, and they are still relatively lightweight. They tend to have smaller housings, which makes them easy to carry through the woods and brush without worrying about bumping them.

While these can be helpful for many hunters, they have a relatively short range when compared with 50 mm lenses. Also, these tend not to transmit light as well during low-light conditions, which means it will be more difficult to hunt at dusk and dawn.

Objective Lenses 50 mm and Greater

50 mm objective lenses, like those examined below, tend to work very well for low-light hunting, and you can use higher magnifications for longer, even as the light starts to dim. They are flexible and easy to use, and they work very well for long-range hunting and shooting.

The scopes with 50 mm objective lenses tend to be durable and able to stand up to the rigors of the hunt. They also provide plenty of light transmission to provide you with a clear picture. They are, however, somewhat heavier, and you may need to have higher mounting rings, which can affect eye alignment if you aren’t careful when aiming.

Two Rifle Scopes to Consider

We’ve decided to include some information on two popular rifle scopes that could be a good choice for your next scope. Both of the scopes in question feature a 50 mm objective lens, and both are durable, making them a good choice for hunting at longer ranges. If you aren’t hunting at those ranges, keep the tips above in mind when you are searching for the right scope for your needs.

Athlon Optics Argos BTR

Athlon Optics Argos BTR

The Argos from Athlon Optics is a 6-24×50 first focal plane rifle scope that features a 30 mm tube and an illuminated APMR MIL reticle. The reticle will remain valid no matter the power settings by growing or shrinking when you zoom in or out.

The lenses are multi-coated, which provide excellent light transmission and brightness in your sight picture. Combined with the 50 mm objective lens, this should provide you with plenty of light even when the lighting conditions are less than stellar.

You will also be pleased to know that it is made from 6061T6 aircraft-grade aluminum that provides excellent strength. It also provides great thermal stability and waterproofing, while also being shockproof.

Mueller AO Eraticator Rifle Scope

Mueller AO Eraticator Rifle Scope

The rifle scope is 8.5-25x magnification with a 50 mm objective lens. It is available in black, as well as silver. Those who will be hunting with the scope will likely want to choose the black option, but it’s ultimately up to your preferences.

The scope has a micro-fine crosshair with a black dot for daylight conditions, along with an illuminated micro-dot for getting on target fast, even at a distance in low-light conditions. There are 11 illumination intensity settings. The scope was designed for those who were taking long-range shots on smaller targets, but it can easily be used to hunt bigger game at long-range.

The turret system has 1/8 windage and elevation click stops, and you will be able to make adjustments with your fingers. While this scope can work well for long-distance, you will find that it can work well for shorter, distances, too. It can focus down to a minimum of 20 yards, making it a very versatile option with a large diameter objective lens.

Conclusion: What Rifle Scope Objective Lens Diameter is Right for You?

When you are choosing between the various rifle scopes on the market, consider the information above when you are looking at the objective lens. You will find that 40 mm and 50 mm can do well for many hunters and shooters, but there are other diameters available, as well. Consider your shooting style and preferences, and always make sure that you are choosing the best quality optics possible.

The 50 mm scopes that we’ve mentioned above can work well for many who want to have a quality scope that can provide them with the brightness and clarity they need without getting in the way or being too heavy. Take the time to find a scope that’s right for you.

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