Scope height measurement with a tapered base, where?

Horsemen

Active Member
Joined
Jan 22, 2008
Messages
35
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.
 

topbrass

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Joined
Feb 24, 2010
Messages
192
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.
 

outofayr

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Nov 20, 2008
Messages
185
Location
Lincoln, NE
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
 

outofayr

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Joined
Nov 20, 2008
Messages
185
Location
Lincoln, NE
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
 

topbrass

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Joined
Feb 24, 2010
Messages
192
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?
 

LouBoyd

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Joined
Oct 15, 2007
Messages
770
Location
Patagonia Mountains, Arizona
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.
 

outofayr

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Joined
Nov 20, 2008
Messages
185
Location
Lincoln, NE
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
 

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