40mm vs 50mm Scope: Which Objective Lens Diameter Is Best?

40mm and 50mm rifle scopes are two of the most popular sizes. There are many factors such as intended use case, scope size, long range accuracy, and budget considerations that shooters need to keep in mind before making a decision.

The size of the objective lens has a direct impact on the overall size, weight, and performance of the overall rifle scope.

In this post, we’ll define what an objective lens is & how to choose between a 40mm vs 50mm scope. We’ll also discuss all the factors shooters need to consider before making a purchase.

What Is An Objective Lens?

An objective lens is the front lens of a rifle scope that is positioned closer to the target. The primary function of the objective lens is for gathering light and transmitting it to the rest of the scope.

Different rifle scopes also have different lens coatings on their objective lenses. These coatings reduce glare, enhance light transmission, and improve overall image clarity.

Objective lenses on gun scopes come in a wide range of sizes to accommodate different shooting preferences. There is no one size fits all best objective lens size. Depending on the situation, a larger or smaller objective lens may be the best option for a rifle scope.

objective lens

How Does Objective Lens Affect A Rifle Scope?

The objective lens in a rifle scope plays a significant role in influencing its performance. Below is a list of ways the objective lens diameter affects performance of rifle scopes.

  • Clarity at long distances – A larger objective lens diameter will provide a more clear image quality at longer distances. Scope glass quality also plays a role in image quality & clarity.
  • Enhanced low-light performance – The size of the objective lens has a direct impact on the amount of light that enters the scope. Larger objective lenses can gather more light.
  • Field of view – A larger objective lens has a larger field of view than smaller objective lenses. Field of view is the amount (horizontal distance) of a shooting environment that can be seen through the scope.

How To Choose Between 40mm & 50mm Scopes?

Here are the 4 factors to consider when choosing between 50mm vs 40mm scopes.

  1. Shooter’s Intended Use Case
  2. Size & Weight Consideration
  3. Long Distance Accuracy
  4. Price Considerations

40mm vs 50mm scope lens

1. Shooter’s Intended Use Case

A shooter’s intended use case for a rifle scope is the most important factor in determining the optimal size of the objective lens. Big game hunters, small game hunters, competition shooters, and tactical shooters will all have different preferences to align with their intended use case.

A hunter targeting small game at shorter distances should be better with a 40mm scope. They do not require the additional range & bulky size of a 50mm scope. The smaller 40mm scope design offers a compact and lightweight setup that is more suitable for quick target acquisition and mobility.

However, a shooter or hunter that is shooting from longer distances should elect to use a 50mm scope. The larger objective lens gathers more light and performs better in dim lighting situations or when shooting at longer ranges. It also allows hunters to get a larger field of view and more easily track game with their scope.

2. Size & Weight Consideration

The size of a rifle scope’s objective lens is important to consider before deciding between 40mm and 50mm scopes. Generally speaking, the larger the objective lens diameter the larger & heavier the rifle scope itself will be.

Scopes with a diameter of 50mm or more will be bulkier & heavier than 40mm scopes. 40mm scopes will be better in situations where shooters are constantly moving and benefit from a lightweight and compact rifle scope. Shooter’s that are more stationary & have rail space for a larger scope will benefit more from using a 50mm scope.

3. Long Distance Accuracy

The importance of long distance accuracy must be considered when making a choice between a 40mm and 50mm objective lens.

A rifle scope with a larger objective lens (50mm or larger) has advantages for long-distance shooting. The larger lens diameter allows more light to enter the scope & so that shooter’s can aim better from long range.

4. Price Considerations

Shooters must consider price before choosing their ideal rifle scope size. The larger the scope the more expensive it will likely cost.

50mm rifle scopes require more material to build and have a higher price tag than 40mm scopes. However, there are many other factors, such as the scope’s brand, features, lens coatings, and overall build quality that impacts the final price.

How Does Firearm Choice Affect Objective Lens Size?

The choice of firearm directly impacts if a 50mm or 40mm objective lens is best for a scope. This is because firearm size essentially determines the available rail space for mounting a scope. Smaller firearms, such as compact handguns or lightweight rifles, have limited to no space for mounting large scopes.

However, most hunting rifles or different AR15s with longer barrels have more than enough mounting space for larger scopes. These guns can fit scopes with larger objective lenses compared to more compact weapons.

Who Makes Large Objective Lens Scopes For AR-15s?

Primary Arms makes the best large objective lens scope for an AR-15. More specifically, their Primary Arms SLX 1-6×24 SFP Rifle Scope is well-known for its glass size & quality. These AR-15 riflescopes with large objective lenses provide a wide field of view & helps shooters shoot accurately from longer distances.

Who Makes Large Objective Lens Scopes For Muzzleloaders?

Leupold VX-Freedom has the best lens quality muzzleloader scope that we’ve tested. Leupold has a long history of manufacturing the best rifle and muzzleloader scopes on the market today. Their line of muzzleloader scopes is know for their improved light transmission, crisp clarity, and precise reticle adjustments.

Who Makes Small Objective Lens Scopes For Shotguns?

Vortex optics is known for developing large & small objective lens scopes for shotgun. They offer a variety of options for shooters for different use cases like turkey hunting, target shooting, or self-defense. Their different shotgun scopes (i.e. Vortex Strike Eagle) provide very high quality objective lenses to benefit a wide range of use cases.

Which Brand Makes The Best Large Objective Lens Scopes For 6.5 Creedmoor Rifles?

Vortex optics also makes the best large objective lens 6.5 Creedmoor rifle scopes. More specifically, the Vortex Viper PST has top-tier glass quality and a larger exit pupil that hunters love. The Vortex Viper PST has proven to be a reliable and popular option among hunters, range shooters, and enthusiasts that value long distance accuracy.

Frequently Asked Questions

Are large objective lens scopes harder to clean?

Large objective lens scopes can sometimes be a bit more challenging to clean due to their larger surface area, but with proper cleaning tools and techniques, maintaining their clarity can be manageable.

Are larger objective lens rifle scopes less durable?

The durability of larger objective lens rifle scopes depends on the manufacturer and quality of construction. While size alone doesn't necessarily dictate durability, it's important to choose a reputable brand and model known for rugged construction to ensure lasting performance.

The Bottom Line

By now you should be an expert on the difference between 40mm vs 50mm scopes. There are clear differences & advantages for choosing each of these popular objective lens sizes. For most applications, we recommend the 50mm scope as it provides more versatile. However, for shooters on a budget or that want a small scope, the 40mm scope is the way to go. Be sure to consider how you plan to use your rifle scope before picking the best option for your needs.

About the author

Patrick Howard

I have been working as a gunsmith for 20 years. Rain, fog, moisture, high temperature, or even snow are all the things a product must withstand in order to be recommended by me.

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