Scope base: 20* or not?

Discussion in 'Long Range Scopes and Other Optics' started by TORCHRIDER, Apr 7, 2011.

  1. TORCHRIDER

    TORCHRIDER Well-Known Member

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    I am buying a one piece scope base for my Savage heavy barrel .223 1/9" twist with Sightron II Big Sky 6-24x. I have a 100 to 1000 yard range to shoot at. Is there any reason why i shouldn't go with a 20* base over a 0* base. Thinking better to have and not need.
     
  2. nitrousmudbogger

    nitrousmudbogger Well-Known Member

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    can be difficult to shoot closer range because you start 20 minute high
     

  3. TORCHRIDER

    TORCHRIDER Well-Known Member

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    How close are we talking?
     
  4. ICANHITHIMMAN

    ICANHITHIMMAN Well-Known Member

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    what?
     
  5. joseph

    joseph Well-Known Member

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    x2

    joseph
     
  6. Eaglet

    Eaglet Well-Known Member

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    Not enough information to help you.

    What is the total vertical adjustment that scope has and is it MOA, MILLS???

    WHAT BULLETS ARE YOU GOING TO BE USING AND WHAT IS AN ESTIMATED MUZZLE VELOCITY?
     
  7. Cordell

    Cordell Well-Known Member

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    TORCHRIDER,

    I will tell you what I did with my 338 Edge and Vortex PST and see if this helps you.

    I have a 20 MOA base and then monted my Vortex in Burris 30mm Signature Zee rings that you can use +10, 0 or -10 inserts. I used the +10 inserts to get a total of 30 MOA. I have about 6-7 moa of adjustment from my 200 yard zero.

    How much MOA adjustment do you have for your elevation turet and is it split in half when the scope is opticaly centered?
     
  8. TORCHRIDER

    TORCHRIDER Well-Known Member

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    My scope has a toal of 60 MOA elevation. With a 20* base will I be able to reach 1000 yet still be able to shoot at 100-200?

     
  9. Eaglet

    Eaglet Well-Known Member

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    To answer your question with the information you're providing above, we will need to make some assumptions:

    Let's assume it's a .223 Remignton
    Let's assume it'll be shooting Bergers VLD 70.0 gr. bullets
    Let's assume you'll have close to 3000 f/sec muzzle velocity
    Let's assume you'll be shooting at sea level
    Let's assume your scope height is 1.8"

    Then After you optically center the scope in the vertical and horizontal direction, move the turrets downwards about 16.2 MOA to be pretty close to zero at 100 yards. That will leave approximately 46.2 MOA of upward adjustment for long range shooting.

    Yes you will have enough adjustment(36.6 MOA) for 1000 yards though the bullet would be subsonic.

    At sea level elevation your max range for supersonic velocities would be about 900 yards and you would need about 29.1 MOA

    The above calculations are mighty close if everything else is where it's suppose to be. :) In any event are very close approximations.
     
  10. MSU Marksman

    MSU Marksman Well-Known Member

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    I just got rid of a 20 MOA base for a 0 MOA on my 6.5x47. I was running a Bushnell 4200 4-16x40 that only has 40 MOA built in, so at 100 yards I was all the way at the top of the scope.
     
  11. Eaglet

    Eaglet Well-Known Member

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    MSU Marksman,

    When your rifle scope is optically centered, using flat base would take about... let's say 3.92 MOA of upward adjustment on the turret to zero your rifle at 100 yards.

    If your scope has a total of 40 MOA, 40/2=20 MOA left from center to all the way to the top. But because you need approximately 3.92 MOA of upward turret adjustment to zero at 100 yards you would only have about 16.08 MOA left of upward adjustment for long range shooting.

    If instead of using a flat 0 MOA base we use a 20 MOA base, now we
    would go like this:20 MOA that you have from your rifle scope, + 20 MOA from the
    base would = 40 MOA. But you'll loose 3.92 MOA.

    Now you would need to turn the turret downwards
    16.08 MOA to be zeroed at 100 yards. That would mean that now you would have
    20+16.08=36.08 MOA left of upward turret adjustment to shoot at long range...

    The only way I could explain your experience would be making the assumption
    that you installed the 20 MOA base backwards; now the scope is aiming upwards
    instead of downwards in relation to the barrel. If that were so, then to zero at 100 yards you would have to dial upward the 20 MOA of the base + the 3.92 MOA
    which would total 23.92 MOA of upward movement when you only had 20 MOA of turret adjustment to begin with. Now you would be all the way to the top on the turret and never on target at 100 yards.

    Hope it helps.
     
    Last edited: Apr 23, 2011
  12. MSU Marksman

    MSU Marksman Well-Known Member

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    Interesting. All I can tell you is that my 20 MOA base was installed correctly, and when I zeroed my scope at 100 yards I had the reticle turned all the way to the top of the scope.
     
  13. Don Ward

    Don Ward Well-Known Member

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    If the reticle was all the way up. You were dialed all the way "down", which makes sense since a 20 MOA base limits downward dialing and increases upward dialing.

    Dialing "up" makes your reticle appear to move down and dialing "down" makes your reticle appear to move up.