Re: Redfield Accu-range
Most of the old Vari XIII series have yardage marked on the power ring. You bracket a 16" or 32" target using the duplex reticle then look on the power ring on the outside of your scope and it has a number corresponding to the the yards. Its the same concept, they don't have the slick little "tombstone" inside the scope giving you the yards. The factory is basically "mapping" the power setting/yardage that the reticle subtends to 16" at. Newer Leupold models may do it as well. All my newer scopes have a mil related reticle.
http://www2.leupold.com/resources/downloads/2011_Rilfescope%20Owners%20Handbook.pdf
Pages 27-28 of the Leupold Scope Manual has some drawings to go along with the text.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">RANGE ESTIMATING WITH VX-3 SCOPES
Selected VX-3 scopes have a built-in range estimator.This system uses the Duplex® portion of the reticle in combination with an additional set of numbers on the power selector ring.In scopes with this feature the space between the tip of the thicker post of the Duplex reticle and the center of the reticle covers 16 inches at 200 yards (the size of a Whitetail buck from backbone to brisket).
NOTE: The Duplex reticle was designed to estimate ranges based on the backbone to brisket dimension of a Whitetail buck. The distance of other game with a body dimen¬sion that is known to be 16 inches (or 32 inches if the measurement is taken from post to post instead of post to crosshair) may certainly be estimated. It is necessary to know the approximate physical size of your target whenever you estimate range.
On scopes with this feature, the numbers facing forward show the scope’s magnification settings.The numbers facing the back are for ranging and show the distances in yards, as shown in Figure C.
To estimate range, follow these steps:
1.View the target through the scope.
2.When targeting an animal with a body that is 16 inches from backbone to brisket, adjust the power selector until that area of the animal’s body fits between the center of the crosshair and the top of the upper heavy post.
3.Read the number on the power selector ring to determine the approximate distance in yards.</div></div>