40mm or 50mm scope

[NDHunter]

Hey everyone, looking for some help. Anyone have a preference for either 40 or 50mm scopes? Obviously a 50mm will be better for really low light but is it worth it? I am looking at a Leupold vx3 CDS. Does it make much of a difference trying to look through the scope since it sits up higher on the barrel? Maybe it is a Ford vs. Chevy debate but I'd like to get some input from you guys if I could. Thanks!

 

[packer58]

Take a look at the Leupold VX-3L, it's contoured objective bell allows it to be mounted on low or medium rings depending on barrel contour, also you can have the CDS turret installed through Leupold's custom shop. With this set up you'll have the best of both worlds, very bright optics with the 50 mm objective and the lower mount. IMO

 

[bigshot]

I can see a big difference in low light between a 36mm and a 40mm scope, so I can imagine a 50mm will be that much brighter.
I own three Leupold VXIII with CDS on my hunting rifles and love them all. Two are the 3.5x10x40mm and the other is a 2.5x8x36mm. My next Leupold will probably be a VX-3L 4.5x14x50mm, also with CDS, because of its design it sits low on the rifle like a 40mm but with the brightness of a 50mm. I don't care for the feel of a regular 50mm scope or bigger, they don't seem to fit my shooting style.

 

[Bitterroot Bulls]

Well it really depends. Apparent brightness is a combination of factors, but the most important one is exit pupil (the little circle of light in the ocular lens). You can calculate your exit pupil: Objective diameter divided by magnification=exit pupil). Notice how when you turn down the magnification on your scope in low light the image gets brighter? So a 3-9X50 would appear brighter than a 3-9X40 at higher powers. The catch is the image doesn't appear much brighter once the exit pupil is larger than 7mm, because 7mm is as large as most people's eyes can dialate.

The 40mm objective scopes are nice in scopes of moderate (say 3-10) magnifications because they provide adequate exit pupils for bright images, and they faciliate a low mounting height, and the subsequent excellent cheek weld. Proper cheek weld is extremely important for precision shooting.

Large objectives are particularly usefull on high-magnification scopes, because they are necessary to get useable exit pupils for low light performance at high magnifications. A 50mm scope at 10x provides a very nice 5mm exit pupil, bu the 40mm scope still provides a perfectly suitable 4mm exit pupil (similar to the 4.2mm exit pupil of your typical 10X42 binocular). Once you get to 15x, the larger objective becomes more beneficial as the 50mm scope now has a useable 3.3mm pupil, while the 40mm scope has a dim 2.6mm exit pupil.

 

[jenbickel]

OMG Vince!! You're alive!
I say, go big or go home. Haha

 

[Ikeepitcold]

50mm is a must for me. With the high country long range hunting we do it makes the biggest difference to me. I have Leupold on 5 of my guns and all are 50mm.

 

[Shaun]

I swear by 50mm

 

[NDHunter]

OMG Vince!! You're alive!
I say, go big or go home. Haha

Yep I'm still alive and well! I've been busy trying to figure out where to hunt this fall.... How have you been?

I saw that you got yourself a new horse. Congrats! Does this mean that I can call you up the next time I am in Wyoming and need someone to pack out an animal?????????

Thanks to everyone for their responses. I'm still not sure which one I'll get but at least I have some good info to help me decide!

 

[jenbickel]

Hahaha!! Well that's a no brainer! You hunt Wyoming in the fall. Duh! And then when I am using my 50mm leupold scope and you're using your 40mm scope and I get the animal, you can watch me pack it out on my horse! Hahaha

 

[Colorado Cowboy]

I'm pretty much old school...reflects my age. My first scope was a new Weaver K3 I got for my 14th birthday, which in their time were great scopes. I now use Leupolds on everything I shoot. I have an older 6x on the same 03 sporterized Springfield that had the Weaver, to a Vari XIII 6 x 20 on my custom .220 Ackley Swift for varmints. I don't care for the 50mms because of the high mounts needed to clear the lens. I have always like to keep my cheek welded to the stock as low as possible...just more comfortable for me and my neck/shoulder relationship. I have not used the Leupold concept of the L series, but I imagine it would fit my criteria. But I have 10 Leupold scopes and it is not really feasible to change them as they all work fine for me.

The only thing that ever bothers me with scopes is the fade out you get from direct sunlight. I can live with that. I have never felt I needed more light gathering ability...when its dark, its dark and I quit hunting and head for camp!

 

[NDHunter]

Hahaha!! Well that's a no brainer! You hunt Wyoming in the fall. Duh! And then when I am using my 50mm leupold scope and you're using your 40mm scope and I get the animal, you can watch me pack it out on my horse! Hahaha

Sorry Jen, doesn't look like I'll be going to Wyoming this year. Hopefully will be going to New Mexico though for elk
I'll be buying another point for Wyoming this year and hope to go there in another year or two. And with my 40mm scope to boot!!

Is that what you have though is a 50mm? Do you put it in a scabbard at all? I've got an Eberlestock J34 and last year when I had my rifle in the scabbard, it was kind of a tight fit even with a 40mm scope so I'm wondering if a 50mm will be too tight.

 

[ChadH]

Bitterroot Bulls gave you some excellent information. The exit pupil is most if not all the equation. One thing that always seems to come into play to me is the tube diameter (1 inch or 30 mm) I personally can't really tell the difference between a 40mm obj with a 30mm tube, and a 50 mm objective with a 30mm tube in practical hunting conditions. I do however find a 40mm with a 30 mm tube brighter than a 50 mm obj with a 1 inch tube. I have no idea the math behind that because exit pupil doesn't really factor in the tube diameter. I always thought of it this way, the limitng factor at some point would have to be the tube diameter. A bigger objective would be fine, but the light still has to pass through a 1 inch tube to get to your eye, or you could give it a bigger hole by going to a 30mm tube. My mind could easily be playing tricks on me though (not an uncommon occurance ). In the end a 40mm with a 30mm tube just mounts up better to me and the check weld is way more comfortable and consistant with the lower Talley rings it lets me use. Someone mentioned the newer Leupolds have an objective end shaped to allow you to mount it lower and that might well be the answer, I haven't tried that yet.

 

[Bitterroot Bulls]

Tube diameter comes up a lot. It does NOT affect brightness!! Ask any optical engineer - I have. The light doesn't fill up the tube on its way through the scope. It follows a narrow path through the erector assembly. The advantage of a larger tube is twofold:

1. Larger tubes have some strength advantages.
2. Larger tubes allow for more internal adjustment (more room for the erector assembly to move).

These are the reasons that the high end long-range tactical scopes have huge 34mm and 35mm tube diamters, not brightness.

 

[ChadH]

Tube diameter comes up a lot. It does NOT affect brightness!! Ask any optical engineer - I have. The light doesn't fill up the tube on its way through the scope. It follows a narrow path through the erector assembly. The advantage of a larger tube is twofold:

1. Larger tubes have some strength advantages.
2. Larger tubes allow for more internal adjustment (more room for the erector assembly to move).

These are the reasons that the high end long-range tactical scopes have huge 34mm and 35mm tube diamters, not brightness.

I kind of figured as much... like I said, I am probably crazy (my wife would tell you that is for sure the case). It just always seemed to me that the my scopes with a 30mm tube were brighter, but then I should probably figure in the fact that those a better scopes to begin with. I do haowever really like using low rings, and the last time I was buying a scope the new Leupold design on the Objective end wasn't available, so I always stayed away from 50MM tubes. That is probably personal preferance though.

 

[Bitterroot Bulls]

You're not crazy Chad, we see what we see. The bigger-tube-brighter thing is a common misconception that was actually started by riflescope marketers in their advertising. Of course, they were full of it, and it did sell scopes.

If you want a bright scope in low light, just get a big enough exit pupil. a 4X32 (8mm exit pupil) scope will be noticeably brighter than a 4-14X50 scope on 15x (3.5mm exit pupil) of similar quality. Now the big scope will get brighter as you dial down the magnification, of course.