40mm or 50mm objective

Discussion in 'Long Range Scopes and Other Optics' started by cornchuck, Oct 9, 2010.

  1. cornchuck

    cornchuck Well-Known Member

    Sep 14, 2009
    I know this question has been answered many times. But which would be better for hunting and target shooting up to 1000 yards. 40 or 50mm objective lens

    Jason gun)
  2. trebark

    trebark Well-Known Member

    Jan 16, 2008

  3. Gunpoor

    Gunpoor Well-Known Member

    Apr 28, 2007
    I have had three Leupold scopes (my three kids have them on the rifles I gave them) and two of them had 40mm objective lens and one had a 50mm, other than that they were identicle. The scope with the 50mm objective was clearer and brighter at all power settings. Shooting long range, which to me means over 600 yds, requires higher magnification, and high X requires more light to make it useable, and this means a bigger front lens to allow more light to reach your eye. I have a Varmint scope (6x-24x X 50mm) and when set on 24X there has to be bright sunlight because if it is a dreary overcast day the sight picture is very dim.
  4. LouBoyd

    LouBoyd Well-Known Member

    Oct 15, 2007
    The primary disadvantage of the 50 over the 40 is more weight. The weight of a lens goes up with about the cube of it's diameter. Recoil puts more strain on mounts holding heaver scopes, also with lighter rifle and heavier cartridges. You also have to carry the scope and rifle. Maybe you just shoot close to your truck and weight doesn't matter or maybe you climb mountains. You didn't say, but it should be considered in making your choice,

    Looking through several hundred yards of sun warmed atmosphere the 40 will give a bit more jittery images. The 50 will be a bit more blurry but that difference is small. Neither is diffraction limited at magnifications used for hunting or long range target shooting. Image resolution is nearly always atmosphere limited.

    An advantage of a 50 is to give a few more minutes of light at sunrise and sunset or better resolution in low light (moonlight) where you can barely see in color.

    In my opinion a more important consideration in picking a scope is the contrast when looking into shadows near sunset. Poor contrast comes from off axis sunlight scattering off the scope's optical and internal opaque surfaces, including the eye and the eyepiece. That's what really separates well designed rifle and spotting scope from junk. Scope specifications generally don't give a good comparison, nor does advertising hype.

    I prefer to compare scopes by looking at a hill with trees with the sun a few degrees above your line of sight, as you would find about a half hour before sunset or after sunrise on a clear day. It should be around the distance you expect to shoot. Scattered light will "wash out" the image. Sunshades can help as does wearing a hat which keeps direct sunlight off of the eyepiece and your eye.

    Rifles scopes should be optimized for aiming the rifle. For finding game binoculars give much better results with their large field of view. They can be light weight too.
  5. dig

    dig Well-Known Member

    Sep 19, 2010
    Totally agree with these comments. The 50 will provide better low light transmission at higher power which is very important in the hunting "golden hour" The quality of the scope matters very much you are buying good quality in Leupold. I am debating a new purchase myself for a lite weight rifle and really have a hard time putting a 1 inch tube on something for even more of the same reasons.