40mm vs 50mm Scope: Which Is Better for Hunting?
When choosing a hunting rifle scope, one of the most noticeable differences is objective lens size. Two of the most common options are 40mm and 50mm scopes.
A 50mm objective can provide a larger exit pupil and more low-light capability at the same magnification, while a 40mm scope is generally lighter, more compact, and easier to mount low on the rifle.
So which is better for hunting?
For most hunters, a quality 40mm scope offers an excellent balance of optical performance, weight, and handling. A 50mm scope becomes more attractive when you regularly hunt in fading light or use higher magnification where maintaining a useful exit pupil matters.
The right choice ultimately depends on your hunting environment, typical magnification, shooting distance, and how much weight you’re willing to carry.
What Does 40mm or 50mm Mean on a Scope?
The number refers to the diameter of the scope’s objective lens, measured in millimeters.
The objective lens is the large front lens closest to the target.
A 40mm scope has a 40mm objective, while a 50mm scope has a 50mm objective.
A larger objective can collect more incoming light, but objective diameter doesn’t tell the entire story about how bright or clear a scope will appear. Glass quality, optical coatings, transmission, resolution, contrast, and magnification all affect real-world performance.
The NRA notes that 40mm and 50mm objectives are among the common sizes used on riflescopes, with larger objectives offering advantages in low-light situations but adding weight and mounting considerations.
40mm vs 50mm Scope: What’s the Difference?
| Feature | 40mm Scope | 50mm Scope |
|---|---|---|
| Objective size | 40mm | 50mm |
| Low-light potential | Very good | Better at comparable magnification |
| Exit pupil at same magnification | Smaller | Larger |
| Weight | Generally lighter | Generally heavier |
| Mounting height | Usually lower | Usually higher |
| Portability | Excellent | Less convenient |
| Rifle balance | Easier to maintain | Can be more front-heavy |
| Best use | General hunting | Low-light and higher-magnification hunting |
| Typical advantage | Compact and versatile | More exit pupil and light-gathering capability |
The difference becomes most meaningful when you compare the two scopes at the same magnification.
40mm vs 50mm: Understanding Exit Pupil
Exit pupil is one of the most important concepts when comparing objective sizes.
The calculation is simple:
Exit pupil = objective diameter ÷ magnification
For example:
40mm scope
At 8x:
40 ÷ 8 = 5mm exit pupil
At 10x:
40 ÷ 10 = 4mm
At 12x:
40 ÷ 12 = 3.3mm
50mm scope
At 8x:
50 ÷ 8 = 6.25mm
At 10x:
50 ÷ 10 = 5mm
At 12x:
50 ÷ 12 = 4.2mm
So at the same magnification, the 50mm objective produces a larger exit pupil.
That’s one of its primary advantages.
Why Exit Pupil Matters for Hunting
Exit pupil represents the diameter of the beam of light leaving the scope and reaching your eye.
A larger exit pupil can be particularly useful when ambient light is fading because your eye’s pupil becomes larger in dim conditions.
However, an extremely large exit pupil isn’t automatically useful. If the exit pupil is substantially larger than your eye’s pupil, your eye cannot use all of that available light.
This is why a 50mm scope doesn’t automatically produce a dramatically brighter image than a 40mm scope in every situation.
The advantage becomes more meaningful when you’re using enough magnification that the 40mm objective produces a smaller exit pupil.
For example:
40mm at 10x = 4mm
50mm at 10x = 5mm
That difference can matter more during low-light hunting than the difference between the same scopes at lower magnification.
Is a 50mm Scope Brighter Than a 40mm?
At the same magnification and with comparable optical quality, a 50mm objective can provide a larger exit pupil and greater light-gathering capability.
But 50mm does not automatically mean brighter in every real-world situation.
A premium 40mm scope with excellent glass and coatings can outperform a lower-quality 50mm scope.
The NRA specifically cautions hunters not to compensate for poor glass or inadequate coatings simply by choosing a larger objective.
That makes optical quality extremely important.
When comparing scopes, consider:
- Glass quality
- Lens coatings
- Light transmission
- Resolution
- Contrast
- Exit pupil
- Magnification
- Reticle visibility
Objective diameter is only one part of the equation.
Advantages of a 40mm Hunting Scope
A 40mm objective remains popular because it offers an excellent balance for general hunting.
Lighter Weight
A smaller objective generally contributes to a lighter, more compact optic.
That can be a significant advantage when you’re carrying a rifle through mountains, timber, or rough terrain.
For hunters who walk several miles during a hunt, shaving weight from the rifle can be more valuable than gaining additional low-light capability.
Lower Mounting Height
A 40mm objective is usually easier to mount lower over the bore.
A lower scope position can make it easier to establish a consistent cheek weld and comfortable shooting position.
By comparison, a 50mm objective may require taller rings to provide adequate clearance between the objective bell and the rifle or barrel.
The American Hunter specifically identifies higher mounting height and potential cheek-weld issues as tradeoffs associated with larger objectives.
Better Portability
A compact 40mm scope is easier to carry and less likely to feel bulky on a lightweight hunting rifle.
This can be especially useful for:
- Mountain hunting
- Backcountry hunting
- Spot-and-stalk hunting
- Long hikes
- Lightweight rifle builds
Excellent for Daylight Hunting
If most of your hunting takes place during full daylight, a 40mm objective can provide more than enough optical performance.
There is little reason to add weight and bulk simply because a larger objective is available.
Advantages of a 50mm Hunting Scope
A 50mm objective has its own important advantages.
Larger Exit Pupil
At the same magnification, a 50mm objective produces a larger exit pupil than a 40mm objective.
This can be useful when hunting during dawn, dusk, or other low-light conditions.
Better Suited to Higher Magnification
One of the biggest practical advantages of a 50mm objective is maintaining a useful exit pupil at higher magnification.
For example:
A 40mm scope at 12x produces approximately a 3.3mm exit pupil.
A 50mm scope at 12x produces approximately a 4.2mm exit pupil.
That difference can be valuable for hunters who need more magnification while light levels are declining.
Useful for Open-Country Hunting
Open-country hunters may spend more time using higher magnification to identify animals at greater distances.
A 50mm objective can provide additional optical flexibility in this type of setup, particularly when combined with good glass and appropriate coatings.
Better for Dedicated Low-Light Setups
If your hunting routinely extends into the final minutes of legal shooting light, the additional exit pupil provided by a 50mm objective can be worthwhile.
That doesn’t mean every hunter needs one.
It means the additional objective size has a specific purpose.
40mm vs 50mm for Low-Light Hunting
This is where the 50mm objective has its strongest argument.
Imagine two otherwise similar scopes.
At 10x:
- 40mm = 4mm exit pupil
- 50mm = 5mm exit pupil
At 12x:
- 40mm = 3.3mm
- 50mm = 4.2mm
The 50mm objective maintains a larger exit pupil as magnification increases.
This can be useful when you’re trying to combine higher magnification with fading light.
However, a high-quality 40mm scope used at a moderate magnification can still perform very well in low light.
For example, a 40mm scope at 6x provides approximately a 6.7mm exit pupil.
That is why the question shouldn’t simply be:
“Is 50mm brighter?”
Instead ask:
“What magnification will I actually use when the light is fading?”
40mm vs 50mm for Deer Hunting
For typical deer hunting, a 40mm objective is often an excellent choice.
Many whitetail hunters spend most of their time in timber, fields, food plots, or stands where extreme magnification isn’t necessary.
A 40mm scope can provide:
- Lower weight
- Lower mounting height
- Good field handling
- Plenty of daylight performance
- Useful low-light capability with quality glass
A 50mm objective becomes more appealing if you regularly hunt during the first and last minutes of legal light or need higher magnification for open fields.
The best choice depends more on the complete scope configuration than objective size alone.
40mm vs 50mm for Elk Hunting
Elk hunting introduces a different consideration: weight.
Mountain elk hunters may carry their rifles over significant distances and elevation changes.
In that environment, a lightweight 40mm scope can be very attractive.
A 50mm scope can make sense when:
- Low-light performance is a priority
- Higher magnification is frequently used
- The rifle is primarily used in open country
- Weight is less important than optical capability
For a lightweight mountain rifle, however, a large objective may add weight without providing a meaningful advantage for the way the scope is normally used.
40mm vs 50mm for Mountain Hunting
Mountain hunting often favors compact equipment.
Every additional ounce becomes noticeable when you’re climbing steep terrain with a rifle, ammunition, optics, and other gear.
A 40mm objective can offer a strong balance of:
- Optical performance
- Weight
- Compactness
- Lower mounting height
- Maneuverability
A 50mm objective can still be useful, particularly for hunters who expect longer shots in open country and need higher magnification during marginal light.
The best choice depends on whether your priority is maximum optical capability or minimum carried weight.
Does a 50mm Scope Require Higher Rings?
Often, yes.
The larger objective bell needs sufficient clearance from the rifle and barrel.
That can require taller scope rings than a comparable 40mm optic.
Raising the scope can affect:
- Cheek weld
- Eye alignment
- Shooting comfort
- Scope height above bore
- Overall rifle handling
The American Hunter specifically identifies higher mounting requirements as one of the disadvantages of larger objectives.
This doesn’t make a 50mm scope a bad choice. It simply means the entire rifle-and-scope setup should be considered together.
Does a 50mm Scope Make a Rifle Too Heavy?
It can.
The actual weight difference depends on the scope model, not just objective diameter.
A lightweight 50mm scope can weigh less than a heavy 40mm precision optic, so objective size alone doesn’t determine total weight.
Still, larger objectives generally contribute to larger and heavier scope designs.
For hunters who spend most of the day carrying their rifles, that difference can matter.
40mm vs 50mm: Which Has Better Field of View?
Objective diameter itself does not determine field of view.
Magnification and optical design have a much greater effect on field of view.
A 40mm and 50mm scope with similar magnification ranges may have different fields of view depending on their optical designs.
Generally, lower magnification provides a wider field of view, which can be valuable in thick timber and close-range hunting.
So don’t buy a 40mm scope simply because you think it automatically provides a wider field of view than a 50mm scope.
Compare the manufacturer’s actual field-of-view specifications.
40mm vs 50mm: Which Is Better for Long-Range Hunting?
For longer-range hunting, a 50mm objective can have an advantage when you use higher magnification.
The larger objective helps maintain a larger exit pupil at those higher settings.
For example, if you frequently use 12x:
- 40mm = approximately 3.3mm exit pupil
- 50mm = approximately 4.2mm exit pupil
However, a 40mm scope can still be an excellent long-range hunting optic if its optical quality is high and the magnification is appropriate.
The 50mm objective doesn’t make the scope inherently more accurate.
It primarily provides additional optical capability.
40mm vs 50mm: Which Is Better for Hunting at Dusk?
If low-light hunting is a major priority, the 50mm objective has the advantage at comparable magnification.
But don’t overlook the rest of the optical system.
A high-quality 40mm scope with excellent coatings and glass can perform extremely well.
The best low-light hunting scope should be evaluated based on:
- Exit pupil
- Light transmission
- Glass quality
- Contrast
- Resolution
- Reticle visibility
- Magnification
- Objective diameter
A larger objective is helpful, but it cannot compensate for poor optical quality.
Does Glass Quality Matter More Than Objective Size?
In many cases, yes.
A scope isn’t simply a light bucket.
The light entering the objective has to pass through the entire optical system before reaching your eye.
Glass quality, coatings, internal optical design, contrast, and resolution all influence what you actually see.
This is why a quality 40mm hunting scope can be a better choice than a budget 50mm scope.
If you’re deciding between two scopes, don’t look at objective diameter in isolation.
Compare the complete optical system.
40mm vs 50mm Scope: Which Should You Buy?
Choose a 40mm scope if you prioritize:
- Lightweight equipment
- Compact size
- Lower mounting height
- Mountain or backcountry hunting
- General-purpose hunting
- Mostly daylight hunting
- Moderate magnification
- Easy rifle handling
Choose a 50mm scope if you prioritize:
- Low-light hunting
- Higher magnification
- Open-country hunting
- Longer shooting distances
- Larger exit pupil
- Maximum optical performance over minimum weight
Neither is universally better.
The right objective size depends on how the rifle and scope will actually be used.
40mm vs 50mm Hunting Scope: Quick Decision
| If You Mainly… | Better Choice |
|---|---|
| Hunt during daylight | 40mm |
| Carry the rifle long distances | 40mm |
| Hunt steep mountain terrain | 40mm |
| Want the lowest practical mounting height | 40mm |
| Hunt mostly inside moderate distances | 40mm |
| Hunt frequently at dawn and dusk | 50mm |
| Use higher magnification in low light | 50mm |
| Hunt open country | 50mm |
| Want maximum exit pupil at higher power | 50mm |
| Don’t mind additional weight | 50mm |
What Matters More Than 40mm vs 50mm?
Objective diameter shouldn’t be the first or only specification you compare.
Also consider:
Glass Quality
Better glass can provide greater clarity, resolution, and contrast.
Lens Coatings
Quality anti-reflective coatings can improve useful light transmission.
Magnification
Think about the magnification you actually use rather than simply buying the highest magnification available.
Exit Pupil
Calculate the exit pupil at the magnification where you expect to hunt most often.
Reticle
A reticle that remains visible in changing light can be more valuable than additional objective diameter.
Weight
Consider the complete rifle-and-scope weight, especially for mountain and backcountry hunts.
Mounting Height
Make sure the objective allows a practical mounting position and comfortable cheek weld.
Final Thoughts
So, is a 40mm or 50mm scope better for hunting?
For most hunters, 40mm is the better all-around choice because it provides a strong combination of optical performance, manageable weight, compact size, and practical mounting height.
A 50mm scope is the better choice when low-light performance and higher magnification are priorities. Its larger objective provides a larger exit pupil at the same magnification, which can be particularly useful during dawn and dusk.
The key is not to assume that bigger automatically means better.
A high-quality 40mm scope can outperform a lower-quality 50mm optic. And a 50mm scope may provide little practical advantage if you rarely hunt in low light or rarely use high magnification.
Choose 40mm for balance and portability. Choose 50mm when you need additional low-light capability and are willing to accept the extra size and weight.
For most hunting rifles, the best objective size is the one that gives you the optical performance you actually need without compromising how comfortably you carry, mount, and shoot the rifle.
Frequently Asked Questions
Is a 40mm or 50mm scope better for hunting?
A 40mm scope is generally better for hunters who prioritize weight, portability, and versatility. A 50mm scope is better suited to hunters who frequently hunt in low light or use higher magnification.
Is a 50mm scope brighter than a 40mm?
At the same magnification and with comparable optical quality, a 50mm objective produces a larger exit pupil and can provide greater low-light capability. However, glass quality and coatings also have a major effect on perceived image quality.
Is a 40mm scope good for low-light hunting?
Yes. A quality 40mm scope can perform very well in low light, particularly when used at moderate magnification. For example, a 40mm scope at 6x produces an approximately 6.7mm exit pupil.
Is a 50mm scope worth it for deer hunting?
It can be worth it if you regularly hunt during dawn and dusk or use higher magnification in open country. If most of your hunting occurs during daylight at moderate distances, a quality 40mm scope may be the more practical choice.
Is 50mm better than 40mm for elk hunting?
Not necessarily. A 50mm objective can provide additional low-light capability, but a 40mm scope may be preferable for mountain elk hunting because it can reduce the weight and bulk of the rifle.
Does a 50mm scope require higher rings?
Often, yes. The larger objective bell may require additional clearance from the barrel, which can require taller rings and raise the scope’s mounting height.
Does objective size affect exit pupil?
Yes. Exit pupil is calculated by dividing objective diameter by magnification. A 50mm objective therefore produces a larger exit pupil than a 40mm objective at the same magnification.
Does a bigger objective make a scope better?
No. Larger objectives can improve low-light capability and maintain a larger exit pupil at higher magnification, but they also add size, weight, and mounting considerations. Optical quality remains extremely important.