3-9 x 40 vs. 3-9 x 50


March 15, 2011, 05:43 PM
I picked up a Redfield 3-9 X 50 for basically 1/2 price. I am very new to hunting. In speaking with a supposed knowledgeable fellow, he basically said it was a poor choice to buy this. The game is Florida deer. I do not understand why the big deal (or potential big deal) of a scope that is 10mm difference.

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March 15, 2011, 05:56 PM
Not sure how he came to that conclusion. When I lived in FL all I ever used was a 3-9 X 40. The 50 requires higher mounts if I'm thinking correctly.

March 15, 2011, 05:59 PM
50mm glass of equal quality costs a lot more. If you buy 40mm vs 50mm at near the same price point the 40mm will generally have better glass and will more than compensate for the larger glass's potential advantages.

March 15, 2011, 06:16 PM
If glass and internals are the same, 50mm always beats 40mm for brightness. The only disadvantge is weight and mounting height.
As jmr stated, 50s cost more for equal quality.

March 15, 2011, 06:51 PM
If you got a 1/2 price deal on a Redfield revolution then I dont see a problem.....

I have a Redfield revolution 4x12x40 Since getting it zero'd in I have shot about a hundred or so round of 30-06 with no more adjustment needed. It has held zero, and allow for good light. It seems on par with all the scopes I have in the $250 to $350 range.

As I understand it Redfield is now owned by Leupold and manufactured in Oregon.

If you like your glass I wouldn't worry a whole lot about it. If I understand correctly 50mm allows for more light than 40mm.Hopefully someone will chime in and correct me if I'm wrong about that.

Hope you enjoy your new scope....Tentwing

Whoops looks like matrem beat me to the punch ;)

March 15, 2011, 07:10 PM
You bought it right & that's all that matters. Mount it as low as you can, but you'll probably need high rings.

March 15, 2011, 07:56 PM
If you have to crane to get you eye up to the scope, look for a stick-on cheek pad for the butt stock. They make some very nice ones now days :)

March 16, 2011, 12:46 AM
I personally don't care for regular 50mm scopes because unless you have some really good mounts, in order to clear the barrel, the scope has to be mounted higher. Even with the best of mounts it can cause problems. Also, I have been told and have read that until you get above 10X the larger objective doesn't help much. However, having said this, I have a 56 MM objective scope ordered for a build that's in progress. It's a Leupold VX-3L which has the relieved spot on the bottom of the objective lense so it will sit down low over the barrel. This allows you to use lower profile mounts like those made for a 40mm or smaller objective scope which allows you to rest your cheek in the cheek well on the rifle butt and you will be able to shoot tighter groups because your head and eyes will be steady.

March 16, 2011, 01:30 AM
50 MM objective -vs- 40MM just means you are going to have a wider field of view. aka... you are going to see a larger picture at each magnification over the 40MM.

March 16, 2011, 02:17 AM
Lakedaemonian, I believe a 50mm scope will transmit more light than a 40 in addition to a wider field of view. However, what I have read is that it doesn't make much difference below 10 power. Then it starts to really make a difference. The big problem is getting the scope low enough on the rifle where you're neck isn't craining to shoot.

March 16, 2011, 02:21 AM
It's no big deal. You got a buy on a 50mm scope. Good for you.

A 50mm scope has to be mounted a whopping 0.2" higher than a 40, but a lot of 40mm scopes are mounted higher than they have to be. I bought my first 50mm scope last year, and I'm using the same medium rings that were already on the rifle.

A 50mm scope will rarely give you a wider field of view than a 40. More often, it will go the other way.

You're new to hunting, and you're starting out with a 50mm scope. I predict you'll like it, and you'll decide that 50mm is a fine size for a hunting scope. Just like that knowledgeable fellow you mentioned decided about the smaller objectives he started out with.

March 16, 2011, 09:01 AM
3-9 is probably the most common variable size scope today. The 50mm lens well gather more light that a 40mm lens. The 50mm well mount .098 higher than the 40mm, that's less than a tenth of an inch.

March 16, 2011, 12:46 PM
madcratebuilder - Just out of curiosity, how did you come up with that .098" number?

March 16, 2011, 12:55 PM
you did fine, as long as you don't have a problem with high mounting to clear the big objective lens

Dr T
March 16, 2011, 01:17 PM
The surface area of the 50 mm is 56.25% greater than that of the 40 mm. This contributes to the brightness, but the quality of the glass does the rest.

March 16, 2011, 02:06 PM
3-9 is probably the most common variable size scope today. The 50mm lens well gather more light that a 40mm lens. The 50mm well mount .098 higher than the 40mm, that's less than a tenth of an inch.

I was thinking, thickness of the tube walls being equal on both scopes, perhapts .197" higher.

10mm diference in the objective, so 5mm difference in the radius, assuming you only have to take the radius since half of the difference in diameter will be going up away from the center and not down toward the barrel. Then there are 25.4 millimeters per an inch. so 5mm/25.4~197"

35 Whelen
March 16, 2011, 07:40 PM
50 MM objective -vs- 40MM just means you are going to have a wider field of view.

ENTIRELY untrue, though the scope companies would have you believe this. Don't believe me? Here are the specs to a Leupold VX2 3-9x40 and 3-9x50. You'll find they EXACTLY the same field of view.

Leupold VX2 3-9x40 specs (http://swfa.com/Leupold-3-9x40-VX-II-Riflescope-P2565.aspx)

Leupold VX2 3-9x50 specs (http://swfa.com/Leupold-3-9x50-VX-II-Riflescope-P2571.aspx)

The 50mm lens well gather more light that a 40mm lens.
If glass and internals are the same, 50mm always beats 40mm for brightness.

These statements are true only to a certain extent. First and foremost, the largest diameter beam or shaft of light the human eye will accept is about 8mm. So, one can roughly calculate how much "brightness" the human eye will realize when using a scope. This is done by dividing the diameter of the objective lens by the power of the scope. Thus, a 3-9x40mm set at 3X, will permit a 13.33mm shaft of light, but we only realize, at most, 8mm of that amount. Set the scope at 9X and we're talking a 4.4mm shaft of light or less than the human eye can detect/use. That is why we can look through a scope, turn the power ring from 9 down to 3 and see a much brighter "picture"...dial it back up and the picture becomes somewhat dimmer.
So, using the 8mm shaft of light as our reference, this means the 3-9x scope with the 40mm objective is at its best up to about 5x where it still permits the 8mm shaft of light while the 3-9x50mm will give the same relative brightness at 6.25X.
Bottom line is if the optical quality of the scopes are precisely, exactly the same, the scope with the 50mm objective is brighter, but only at slightly higher magnification than the 40mm. IOW, the 3-9x40mm has the same brightness at 5X as the 3-9x50mm does at 6.25X.
Personally, if I can see it/do it at 6.25X, then I can likewise do it at 5X. I've never liked scope with huge objectives on a nice, trim hunting rifle. To me, it's like putting custom mag wheels and big tires on a Rolls Royce. But, to each his (or her) own!

March 16, 2011, 09:05 PM
Good advice 35 Whelen.

For some reason some hunters want to make their hunting rifles LOOK like sniper rifles, but 99% aren't willing to pay the price for the real thing. 50mm lenses look cool,( at least to some) but unless you are willing to spend big bucks for quality 50mm glass you are better off with a decent quality 40mm lense.

By the way a scope mounted .1" higher is a big deal. It makes a big difference in getting a proper mount. Heavy scopes mounted higher are subjected to more recoil forces because of the extra weight and torque which can lead to more scope problems.

Leupold scopes as a whole are about 1/4 lb. lighter and 1.5"-2" shorter than most of the competition. I've always felt that was a big reason they are regarded as tougher and more durable than most of the competition. They are just subjected to much less recoil forces working on them when the gun is fired because of their smaller size.

March 16, 2011, 09:19 PM
I went to replace a scope with a 40mm objective with one having a 50mm lens, and found that it hit the rail with medium-height rings. I had to go back and get high rings to have enough clearance.

35 Whelen
March 16, 2011, 11:08 PM
The "biggest" scopes I own are a couple of Burris Fullfield II's in 3-9x40. One is on my "business" hunting rifle; an old Ruger 77 in 280 Rem. The other is on my Remington 700 Classic in 220 Swift. When I'm hunting, the scopes are always, without exception set on 3X. I've learned that it's really no big deal to shoot at distant game with low powered scopes, but let a buck walk out at 40'-50' when your scope is set on 9X, and your field of view is about 2 FEET, and you may have trouble.
My Scout rifle wears a Burris 2.75X and has accounted for more game than all the other 13 or so centerfire hunting rifles I own combined. My old Ruger 77 in 6mm Rem. likewise wears an olf 4X Redfield and it's all I've ever needed. Ditto for my 35 Whelen which wears a 4X Burris and holds the title for my longest measured shot on game which was exactl 355 lasered yds.

March 17, 2011, 11:08 AM
Had a 50---won't own another----sits up too high.

March 17, 2011, 11:49 AM
I have a problem with high mounted scopes. Found the optics line of sight and the bore (bullet) trajectory to be a problem if you change range to target. For that reason I buy 40mm scopes.. also found that rarely do I use power greater than 6-7x

edit; I like the objective bell to barely clear the barrel

Art Eatman
March 17, 2011, 11:58 AM
See Post #7.

It's no big deal to add a pad to the comb of the stock if need be, so that you get a good cheek weld while easily looking through the center of the scope. Once all that is dealt with, it's just a 3x9.

Generally, I learned that while walking-hunting or sneaky-snaking, keeping the scope on 3X is the best way to go. If sitting and watching over an area where longer shots would be expected, setting the scope to 5X or 6X is fine. I only use 9X on prairie dogs or when sighting in.

March 18, 2011, 02:28 AM
35 Whelen, great post. I think you pegged this whole thread. And I agree with you about the difference between a 40 and a 50mm Objective. However I have heard as the power goes above 10 it really begins to help. I don't know how true this is but I'm going to find out within the next month when my new rifle build is finished because I bought a Leupold 4.5-14X56 with 30mm tube for it. Oh yeah and the objective focus is on the side. In other words it's the most expensive scope this country boy ever thought about buying. Looking back, I could have bought a nice zeise, Smit Und Bender, or a Swarovski for that much. But, buy American I always say. So I'm hoping it will be everything I imagine. For $900 it better be.

March 18, 2011, 02:34 AM
Art, my eyes aren't as good as yours. I can no longer see small objects at 300+ yards at 9x. I just bought a Nikon Buckmaster 6-18X40, and about 12 power things just start to looking good at really long range. Of course 10-20 years back I was using a 6x El Paso Weaver. Time marches on and so does our ability to see and hear well. Don't even ask about my hearing......LOL!

Lloyd Smale
March 18, 2011, 06:25 AM
Only thing i see it adds is a bit of light gathering if you insist on buying a cheap scope. A good scope with good glass will pick up all the light you can use with a 40mm objective. Field of view is related to eye relief but not to objective size. if your comparing two scopes that are identical other then objective size and the 50mm one is noticealby better in low light then the 40mm you basicaly have a scope with pour optics.

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