You might be wondering why we need different sizes in scopes. Does a slight 10mm difference between the two scopes matter?
That’s a good question.
You won’t see the difference if you just put a 40mm and 50mm scope side by side aside from the slight size contrast between the two.
Thus, I compared the 40mm vs 50mm scope to know which one is better for you!
Table of Contents
40mm Scope Overview
When we talk about 40mm, it refers to the objective lens size of your scope.
This lens size can give you a smaller, lighter, and more compact scope tube diameter for your rifle.
I personally like using a 40mm scope because a light transmission at this scope size is already good, especially in brighter contact.
In fact, I can make its performance even better by adding a high-quality glass coating.
You can commonly see a scope with the 40mm objective with the following magnification ranges:
- 3-9x
- 9-25x
- 4.5-14x
- 4-12x
50mm Scope Overview
I used to think that a larger objective lens meant clearer and sharper target images.
However, even a smaller objective lens with better glass quality and coating can beat a bigger one!
So, having a bigger lens diameter does not necessarily mean an immediate edge.
A 50mm objective lens already lets me see a target BRIGHTLY in a low-light environment.
It also provides good and bright image quality even at a longer distance.
In my experience, a 50mm scope has helped me ACE every shot in all my different shooting activities.
Just like the 40mm, you must complement the advantage of a 50mm scope lens with a high-quality lens coating and glasses.
40mm vs. 50mm: What’s the Difference?
You will not know the difference between a 40mm vs. 50mm lens if you don’t look through the scope’s ocular glass lens.
I used to think bigger is always better regarding objective lenses.
But the comparison between the two revolves around which one can give my naked eye BETTER image quality.
Everyone views their optics differently, and it does NOT depend on the size alone.
The scope glass quality can also help provide better image sharpness and brightness, even if the scope size is smaller.
I’ll compare these scope sizes in different essential categories in the scope world.
Intended Use
The kind of shooting or hunting you will do is important!
For example, if you plan to hunt in the day when light won’t be a problem, a smaller objective lens will suffice.
On the other hand, low-light hunting situations require a larger objective lens to let enough light enter the scope.
WINNER: It depends.
Size
Obviously, 40mm is a smaller objective lens than 50mm.
Thus, it provides you with a lower mount profile for better and more comfortable aiming.
Meanwhile, the 50mm objective lens gathers MORE light and gives additional adjustment clicks for shooters.
However, eye alignment and aiming comfortability might be an ISSUE for some of them.
WINNER: 40mm
Weight Consideration
Since a 40mm objective lens is smaller, it is LIGHTER than a 50mm one.
It only adds a little to your rifle’s total weight.
I preferred moving around with the 40mm scope than the 50mm since I didn’t have to carry too much weight.
A wider objective lens like the 50mm gives EXTRA weight to your rifle scope. Thus, I would not recommend it in this situation.
WINNER: 40mm
Magnification Power
With high-quality glass and coating, a 50mm objective lens diameter can already give you a bright image.
A wide objective lens no longer requires much magnification.
This is especially when you need better sight at a distance in LOW LIGHT. Thus, having a 50mm objective lens is better for a long-range scope.
It is a different story for a 40mm scope lens.
You must mostly use magnification to get a better image quality, especially when aiming at darker times and locations.
WINNER: 50mm
Exit Pupil
A LARGER exit pupil size makes BRIGHTER images.
The exit pupil is the diameter of light that passes through the objective lens to your eyes. It is placed at the back of the eye relief, the closest to the human pupil.
Thus, a 50mm scope has a bigger objective lens, therefore, a bigger exit pupil size than the 40mm one.
You can have brighter images in this manner because MORE light transmission via a larger exit pupil size gets to your naked eye.
WINNER: 50mm
Resolution
Unlike the exit pupil, the resolution does not solely depend on the size of objective lenses.
A bigger objective size is useless if your scope has bad lens coating and glass quality.
The 50mm diameter lens for rifle scopes already provides a brighter image than the 40mm.
But, the latter can still offer a better-aiming image if it is higher in quality than the former.
WINNER: 50mm
Frequently Asked Questions
You may still be curious about this scope size comparison and other relevant information. Check out more details on some common questions below.
Is a 50mm Scope Better Than 40mm?
A 50mm scope for rifles is better than a 40mm one, but not in all contexts.
If both have similar accessories and parts, the 50mm rifle scope lens is surely better.
But, it is NOT ALWAYS the case if the 40mm objective lens has better accompaniments.
Regardless of size, your scope will reflect light and cause lens flare if it has a low coating and glass quality.
Thus, you should gather good parts for your scope and make it a COMPLETE PACKAGE.
It may cost more, but it is worth it!
What Scope Is Best for 50 Yards?
The 40mm diameter lens is better for close-distance shooting, like at 50 yards.
A 50 mm diameter lens is suitable for wider field shooting and has more features. However, it does not necessarily mean it is also good at any distance.
Short-range shooting requires smaller guns, and smaller lenses are more compatible.
The 40mm diameter lens is also light for fast movements, aiming, and shooting at a close distance.
Is a 3-9×40 Scope Good for Hunting?
Yes! I have a lot of scopes with this magnification and diameter, and my hunting is always efficient!
This scope model gives you a sense of versatility for short-range and longer-distance shooting.
It provides accurate short-range shots of small to medium-sized animals.
The same applies to lesser accuracy issues in longer-distance firing due to its high magnification range.
So yes, a 3-9×40 scope is GREAT for your hunting activities!
Final Verdict: Which Is Better to Use?
If you look at these categories, there is not much difference.
But in similar parts like the glass and coating quality, I have to give the win to the 50mm objective lens over the 40mm.
Thus, this gives you more choices in buying rifle scopes.
Do you want to choose a 40mm and add good rifle scope parts? You may want to maximize a 50mm diameter advantage with the best available parts.
Conclusion
You should not focus much on the bigger objective diameter size but on the other accessories in your rifle scope as well!
There are MORE factors to be considered, not just the lens size of rifle scopes.
A 50mm is greater than a 40mm as the former has more advantages.
Yet, gearing the latter with better parts like good lens coating and glass quality can still take the win.
In other words, you should gather the best parts to have the best rifle scope.
