Is it measured from the bottom of the rear sight notch to the top of the blade?

How much of a difference in impact height is there between blades that are .060 and .0146

With a set of Calipers.

You need the sight radius, the range along with the different sight heights to calculate the change in impact.

Run the rear sight slide all the way to the left and measure the distance from the bottom to top of the portion extended from the base using a dial caliper or micrometer. The difference in elevation is relative to the sight radius and distance to target. If the sight radius, not barrel length, is 6" and distance to target 25 yards each .001" change is sight height results in .150" difference on the target. (900" / 6". 25 yards = 900 ". So in this case changing the slide from .146" to .160" will result in .150" x 14 or approximately 2.1" in elevation. A shorter sight radius results in more change, and a longer sight radius in less.

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Gunsmithing since 1961