Results 1 to 10 of 10

Thread: Lower mag scopes, larger objective lens: No-go?

  1. #1
    Member
    Join Date
    Apr 2006
    Location
    Fairbanks, AK
    Posts
    554

    Default Lower mag scopes, larger objective lens: No-go?

    I was just told that a larger objective lens (50 mm) on a lower magnification rifle scope (1.5-6x) would be more of a hinderance than a help for shooting under low light conditions. This individual suggested I look at the 20 mm or 24 mm objective lens scopes instead. I thought the Nikon Monarch Gold 1.5-6x, 40 mm, would be a great scope atop my 416. Any opinions out there? thanks. john

  2. #2
    Moderator LuJon's Avatar
    Join Date
    Mar 2007
    Location
    Palmer, AK
    Posts
    11,415

    Default

    The key is the exit pupil size. Divide your objective by the power setting to find the exit pupil size. Most kids with healthy eyes can utilize up to a 6mm exit pupil and most adults (the vast majority of us) can only utilize 5mm. So literally your eye to an extent becomes the limiting factor. To calculate exit pupil the formula is P=D/M where P is your exit pupil, D is your objective diameter and M is your magnification power. With this knowledge we can begin to calculate optimal objective size for the scope magnification we are looking to hunt with.

    a 6X scope will top out on light gathering for most of us at 30mm objective. A child may be able to benefit by stepping up to a 36mm
    A 4x tops out at 20mm objective for most of us and 24mm for a healthy child.

  3. #3
    Moderator LuJon's Avatar
    Join Date
    Mar 2007
    Location
    Palmer, AK
    Posts
    11,415

    Default

    I would also add that eye relief is something you should probably pay attention to with the bigger thumpers. The higher the magnification on most scopes the closer you have to have your eye to the scope. Zeiss is one of the few manufacturers out there who maintains even eye relief across the full range of magnification. Most others force you to creep up on the scope as you crank up the power. Some creep more than others and it is a good thing to test before you strap it onto a rifle that kills at both ends.

  4. #4
    Member hodgeman's Avatar
    Join Date
    Jul 2008
    Location
    Delta Junction AK
    Posts
    4,057

    Default

    Bigger objectives tend to be more common in Europe where shooting after dark is relatively common. A good quality 6x42 is about as bright as scopes get on samples I've used.

    Pretty moot in AK where most of our hunting is in daylight. I dislike big objectives for a variety of reasons but light gathering isn't one of them.
    "I do not deal in hypotheticals. The world, as it is, is vexing enough..." Col. Stonehill, True Grit

  5. #5
    Member
    Join Date
    Apr 2006
    Location
    Fairbanks, AK
    Posts
    554

    Default

    OK, and thank both of you for clearing that up. I presently have a 1-4x, 20 mm scope, and now I think I know why my forehead and it have become intimate on several occasions. I've bled from that mutha little scope, which is stuck at 4x. Perhaps looking at a Zeiss will eliminate the bite I get now and then. I will do some reading about eye relief specs; I know some of the scopes I've looked at recently have bragged about how much you can sit back. Thanks again. john

  6. #6
    Member
    Join Date
    Apr 2006
    Location
    Fairbanks, AK
    Posts
    554

    Default

    Upon more digging, it looks like the Leupolds have about as good of eye relief as any; right around 4" and consistent. I'll have to get my face on my stock and have my eye relief measured w/ my present scope; maybe it is a good as it is going to get, too, as well as the light it gets to the eye. The 30 mm tube, then, is apparently not a big advantage over the 1". ??? So, this advice here may have saved me from buying a new scope for nothing. Thanks. j

  7. #7
    Member hodgeman's Avatar
    Join Date
    Jul 2008
    Location
    Delta Junction AK
    Posts
    4,057

    Default

    Just as a matter of interest.... eye relief is widely variable from one brand to the next. As a general rule- higher magnifications tend to be less forgiving when it comes to eye relief.

    Leupold and Zeiss have excellent eye relief and tend to not be very critical- meaning you can move closer or further back a little without disturbing the sight picture. On rifles of any substantial recoil those two brands are pretty tough to beat.

    I had a very fine scope at one point that had excellent optics but the eye relief was both minimal and critical...I mounted it on a hard kicking rifle and that thing hit me three or four times and I sold the whole mess as soon as I could.

    On a hard kicking rifle also look at your technique as well as how far aft the scope is mounted- I am a habitual stock crawler and I have to work at not getting tagged with some setups.

    General rule for a hard kicking gun is a lower magnification scope, more eye relief, scope mounted as far forward and as low as practical.
    "I do not deal in hypotheticals. The world, as it is, is vexing enough..." Col. Stonehill, True Grit

  8. #8
    Member
    Join Date
    Apr 2006
    Location
    Fairbanks, AK
    Posts
    554

    Default

    Hodge: "General rule for a hard kicking gun is a lower magnification scope, more eye relief, scope mounted as far forward and as low as practical." And a 416 w/ only 175 lbs behind it is a hard kicker. When I sit on the bench at the range, I almost get knocked off the seat. I will surely get the most eye relief I can. j

  9. #9
    Member
    Join Date
    Apr 2006
    Location
    Fairbanks, AK
    Posts
    554

    Default more info

    Some researching has turned up some interesting points. For one, "exit pupil = magnif over objective lens size" is not consistent. For example, (and I've seen a couple of others) Bushnell states this: exit pupil = 14 mm to 2.6 mm on it 2.5-8x32mm Elite 6500 scope. Most of the scopes I looked at have 3.5 (Zeiss) to 4" of eye relief, basically, with the above Bushnell boasting 6". Most of the lower power scopes have a field of view of 60' and 100 yrds. The Nikon Monarch Africa 1-4x20 mm has 90'; huge. Chuck Hawks reviewed the above Bushnell and compared it to the VX3 Leupold in similar magnification: 6 of one, half dozen of the other. I also looked at my scope and it is a Leupold VX II, and my wife measured the eye relief at about 4". As a testament to its durability, it has survived a few hundred rounds atop the 416. So, the next step is to take my scope off and compare it to a couple of others outside the store at dusk. If I can break it loose (stuck at 4x) maybe it will just stay on the rifle. Thanks again for the suggestions of things to consider in researching.

  10. #10
    Member hodgeman's Avatar
    Join Date
    Jul 2008
    Location
    Delta Junction AK
    Posts
    4,057

    Default

    Quote Originally Posted by jklingel View Post
    I also looked at my scope and it is a Leupold VX II, .... If I can break it loose (stuck at 4x) maybe it will just stay on the rifle.
    If your current scope is a Leupold VX II then no need to break it loose....send it in and they'll fix it. It has a lifetime warranty and their customer service is absolutely second to none.
    "I do not deal in hypotheticals. The world, as it is, is vexing enough..." Col. Stonehill, True Grit

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •