rifle scope - 40mm or 50mm?

[Paul in Idaho]

My next major hunting purchase probably will be a Leupold riflescope. I have been using an off-brand 50mm AO scope for the past 15 years. Its optical clarity is fine, but I have had increasing doubts about its reticle stability.

I bought the 50mm with the understanding that larger objective = brighter image. Is that still correct, or can a 40mm be just as bright in poor lighting with the better lens coatings and quality available now?

The 50mm is more expensive more, and heavier, than the 40mm version. I don't plan on buying an AO model again.

Which diameter would you choose, and why?

 

[Deleted member 20812]

It depends on what power you plan on shooting at. The exit pupil is the size of the objective divided by the magnification power. I.e. a 10x bino with a 40mm objective = exit pupil of 4 mm. Your eye can only utilize a maximum of 7mm.

I do most of my shooting at 6x, with a 36mm objective = 6mm exit pupil. Plenty for me. If you plan on doing a lot of shooting at higher magnification, you may want the 50. If you mostly use 4-6x for your shooting, you're wasting your money.

Keep in mind, 7mm exit pupil is the maximum your eye can use. As you age, this can get considerably less.

 

[Gunner46]

It's all in how the lense is coated. If you're going with a Leupold you'll be fine. I never really saw the need to drag around extra weight if not absolutely necessary. And, you'll probably need to go with higher mounts as well.

 

[nrpate05]

The 50mm should allow more light in during low light hunting, but I don't think that is worth lugging the bigger scope around all day and having to use the higher mounts, which I really dislike for whatever reason Probably mostly aesthetic. I have really only used Leupold, but have shot Nikon and Vortex on occassion. I think the VX-2 is probably one of the best values in scopes today or the VX-3 if you can spend a bit more.

 

[sagebrush]

40 MM. It's the largest objective I want on a hunting rifle and I've never had a problem finding a target during hunting hours with a 40 MM Leupold.

 

[schmalts]

50mm will usually give a wider FOV at the same magnification as a 40mm and a clearer image at higher magnifications as well. Brightness differences at moderate magnifications are minimal and unless you are hunting in a state that allows big game hunting without the approximate 20 min before and after sunrise/sunset any brightness gain is no advantage. If you are planning on staying under 12X do not even consider a 50mm. JMO

 

[Gunner46]

There ya go Paul. Straight from the Scope Kahunna !

 

[Rooster52]

To me,I hunt the high country every chance I can and ounces count

 

[SFC B]

I LOVE my Vortex Viper HS 4x16x44......You should definitely give them a look

 

[Ben Lamb]

Agree with Pat, but with the caveat that you should get what you like the best.

 

[MKotur325]

I agree with others on here. Glass and coatings will have more to do with apparent brightness than objective will. I hunted a few years with Leupold VX-II's an the newer VX-2's. I had one situation that limited me to waiting until about 5 minutes after legal shooting light to be comfortable taking a shot on an elk in MT with a 3-9x40 VX-II. It was cloudy, 25 minutes before sunrise, and I was deep in a steep draw. It took an extra few minutes before I could make out enough of the outline of an Elk against the hill behind it to be comfortable taking a shot. One 5 minute delay in 10 years of hunting with that scope isn't in my mind enough to be worth the extra weight and higher mounts of going to a 50mm Objective unless you are going to have 12x+ magnification. If you look at it with leupold. The VX-2 3-9x50 is the same MSRP as the 2.5-8x36 in the VX-3 Line. For the same money. I'd get the VX-3 and drop to 8x magnification while getting better glass, better coatings, and better low light performance.

 

[Ben Lamb]

I've got both the VX 2 & the VX3 in MKotur's post. Absolutely agree. My VX2 hasn't ever failed me excpet when it was heavily overcast and I couldn't get a detailed view of a whitetail at 150 yards. I should have just trusted Rat Fink and shot it because by the time it was light enough to see, I had screwed up the shot so bad I missed - twice.

I'm very happy with both, and like the slim lines of the 2.5x8 a lot more than the 3x9.

 

[mtmander]

I use a 5-20 x 50mm for varmint hunting where long shots are possible. I would not use that scope when I have to go up and down mountains due to the size and weight.

 

[danr55]

A 40mm objective with a 30 or 34 mm tube will transmit more usable light than a 50mm objective on a 1" tube.

 

[1_pointer]

A 40mm objective with a 30 or 34 mm tube will transmit more usable light than a 50mm objective on a 1" tube.

Any link/source to the actual physics showing that to be the case?

 

[Paul in Idaho]

Thank you everyone. There is some great info here to think about.

 

[stillkickin]

The 50mm should allow more light in during low light hunting, but I don't think that is worth lugging the bigger scope around all day and having to use the higher mounts, which I really dislike for whatever reason Probably mostly aesthetic.

In my stable I have one 50mm Leupold, and I agree 100% with nrpate. It is a great scope performance wise as are all of my Leupolds.

 

[fishing4sanity]

The 50mm objective is going to require taller rings to mount the scope, if you like to get a good solid cheek-weld to the stock the taller rings make that harder to do. Also, if you use a scabbard on a saddle or some of the backpacks, that bigger bell on the end of the scope interferes a little more. At the same time, I know a lot of guys who really like their 50mm scopes.

 

[Big Billy]

I have 2 leupold 6.5 -20 Vari x 3's one with a 40 mm and the other is a 50 mm AO and I can't tell the difference in field of view just my 2 cents worth..good luck with your choice

 

[schmalts]

Any link/source to the actual physics showing that to be the case?

The larger tubes give the benefit of more adjustment for your turrets. You cannot get enough adjustment from a 1" tube to use it for something like F-class or other long range shooting where you are dialing in the drop and wind.