Scope height measurement with a tapered base, where?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Horsemen, Mar 23, 2010.

  1. Horsemen

    Horsemen Active Member

    Messages:
    35
    Joined:
    Jan 22, 2008
    Just a stupid question…Where the heck would you make the measurement for sight height, with a tapered base?
    Seams to me, that it would be the center of the scope. Not on the ends. Any thoughts.

    Regards Mike.
     
  2. tom m.

    tom m. Well-Known Member

    Messages:
    82
    Joined:
    Jan 17, 2009
    i have always done it at the center. my thought behind it was,....thats where the reticle adjustment is so..
    tom
     
    Last edited: Mar 24, 2010

  3. topbrass

    topbrass Well-Known Member

    Messages:
    192
    Joined:
    Feb 24, 2010
    I dont own a scope that has the reticle in the center. It is usually well back toward the eye piece. But the center would appear to be a logical place to start. You would just have to remember to add the moa increase from the start if you use a ballistic table or program.
     
  4. outofayr

    outofayr Well-Known Member

    Messages:
    185
    Joined:
    Nov 20, 2008
    Actually, you don't add the MOA on the base to a ballistics program, at least not the ones I use. The tapered base just allows you to use more of your scopes adjustment to dial up. By mounting on a tapered base, the crosshairs are positioned more to one end of their travel, allowing you to dial up more elevation to shoot the longer ranges...

    Brian
     
  5. topbrass

    topbrass Well-Known Member

    Messages:
    192
    Joined:
    Feb 24, 2010
    So how do you measure the height of the scope with a 20moa base?
     
  6. outofayr

    outofayr Well-Known Member

    Messages:
    185
    Joined:
    Nov 20, 2008
    Center of tube at knobs. That is your reticle center. That won't really change that much with a 20 MOA base vs a flat base, but the angle you're looking down the scope does...that's how you get the extra 20MOA of adjustment on the base...

    The input of sight height above the bore just gets you in the ballpark, anyway - you still need to go shoot your drops :)

    Brian
     
  7. topbrass

    topbrass Well-Known Member

    Messages:
    192
    Joined:
    Feb 24, 2010
    I have never seen a reticle located at the knobs. All the scopes I have ever seen has the reticle just in front of the ocular lens behind the knobs.

    Which scope has the reticle under the knobs?
     
  8. LouBoyd

    LouBoyd Well-Known Member

    Messages:
    770
    Joined:
    Oct 15, 2007
    In my opinion all external ballistics measurements should be made from the rifles muzzle. That's the point where the bullet starts to drop, and that's the point where the computations for atmospheric drag begin to be applied in external ballistics programs. For the purposes of determining the bullet trajectory relative to the line of sight all ballistics programs I know of are doing their calculations relative to the muzzle, and (in my opinion) the proper scope height to use is the line of sight from the optical center of the objective lens to the target center which is at the rifles zero distance. That distance can be anything the shooter chooses. The "scope height" is the vertical distance between that line of sight and the point where the centerline of the rifles bore intersects the plane of the crown.

    A wedged base really has nothing to do with it as that may be canceled by an offset reticle in the scope. The line of sight does not have to be parallel to the optical or mechanical centerline of the the scope, but the optical centerline and the line of sight to the zero target will intersect within the objective lens. The scopes tube will normally be centered on the optical centerline but that's up to the scope's mechanical designer, not any law of optics.
     
  9. outofayr

    outofayr Well-Known Member

    Messages:
    185
    Joined:
    Nov 20, 2008
    Basically what I was trying to say:)

    You have to measure somewhere to have the input into the program, so I was just stating where I standardized on. I didn't say that I was measuring on the reticle, but rather trying to measure on the centerline of the line of sight.

    Do whatever you want - it all still has to be shot out anyway.

    YMMV, BIDI.

    Brian