Larry's Use Of The Duplex Crosshair
How to use the Scopes Duplex range-finding reticle. The secret to being able to quickly estimate the range to your target is in knowing the size of your target. Where the crosshairs go from thick to fine is referred to here as an "APEX". The Scopes duplex or 30/30 range-finding reticle is based on a "APEX to APEX" area of 30 inches at 100 yds @ 4x power.
The average size buck has a body of 30 inches in scope at 100 yards; so if it appears to fill the point to point area @ 4x power it is 100 yds away. If it only fills half the area (called "point to crosshair") it is 200 yds away, and so on, as shown in the illustration: The following table shows the target ranges, based on a 30 inch target at various powers and whether the target fills the "point to point" area or the "point to crosshair" area (ie half the "point to point" area).