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50mm vs 40mm Objective +/-

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/26/2009 at 11:05
bookworm View Drop Down
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Can someone outline for me the advantages/disadvantages when deciding between objective lens diameter?

As far as I can tell the main advantage of 50mm is light transmission, with the main disadvantage being size/weight/cost.

What other important considerations are there?


PS - Sorry if this topic has been covered plenty here, but after some searching I couldn't find much.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/26/2009 at 11:17
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I have both and feel that it depends on what kind of hunting you are doing. If it's a slow going stalking type hunt in low light where weight and bulk are not an issue, I use the 50mm. When I have to cover a lot of ground, I want a light rifle and a light scope with good optics, this is where a 40 comes in. Less bulk, lower mounting, less weight in an all around scope, probably the 2.5-8x36mm class is my best all around as long as it's tough and has good glass. I can look out across my back field early in the morning at a grove of trees that deer bed in all year and make a fair judgement of field conditons. As near as I can tell the better glass is way more important than bigger glass!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/26/2009 at 11:26
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I find that I have a more consistent rest when looking through the lower profile 40/42mm but I generally use 50mm because of the additional low advantages. Bucky
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/27/2009 at 00:50
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I've read a lower mounted scope is supposed to provide more accuracy, personally I'm not sure how it works but I've seen it written many times.
 
Curious how much difference there is and how much that difference varies at longer ranges.  I'm pretty sure it can't be too bad for accuracy since many 1,000+ yards shooters use 50/56mm objective scopes.
 
Just in looks alone I think a 1" tube scope with a 50mm objective doesn't look right, especially if it is an abrupt enlargement from the mounting portion to the objective.  When it is lengthened out and especially with a 30mm tube, it can look nice.  A 13" scope with 50mm objective looks like an ugly flashlight on top of a rifle though.
 
Also a 50/56mm objective needs good glass and coatings or it will not give you the brightness advantage...so it's just extra size, weight, higher off bore axis for no good reason.  Example - a Millett TRS with 50mm objective (4-16x50) I got to look through today was not as bright as the 40mm objective Nikon Buckmasters (3-9x40) at the same store.
 
And a Fullfield 2 3-9x40 was very, very bright at 3-5x but seemed dimmer at 9x than the Buckmasters at 9x....so definitely check the exact scope you are thinking about regardless of objective size.  Obviously their light transmission % numbers mean nothing as well...
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/27/2009 at 06:20
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 Just to add to what these guys have already said:
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/27/2009 at 09:36
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Originally posted by danjojoUSMC danjojoUSMC wrote:

I've read a lower mounted scope is supposed to provide more accuracy, personally I'm not sure how it works but I've seen it written many times.
 
 
The lower the optic, the better the cheek weld. With a better cheek weld, better accuracy potential can incur, perhaps?  
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