RETICLE RANGEFINDING RIFLESCOPES OFFER A SIMPLE WAY TO CHECK OR COMPUTE RANGE. HERE’S HOW. ometimes it seems rifle shooters went directly from “guesstimating” ranges to laser precision, but before lasers there was a more accurate alternative than guessing. More shooters should probably know how to use it, just in case their laser doesn’t work, or as a check on laser results. S JOHN BARSNESS Reticle ranging is based on a principle of geometry called the subtended angle, defined as “the angle formed by an object at some external point.” Any reticle subtends a certain angle at certain ranges. Let’s say we’re using a simple plex-type reticle, and aiming at a typical target marked in 1-inch squares at 100 yards. As an example, we’ll say the tip of KEITH’S METHOD the reticle’s bottom post is 6 squares (6 inches) Eventually I found a plex below the crosshairs. reticle was more accurate, This is called subtending and I learned how primar6 inches at 100 yards. ily by reading Elmer Keith, If we aim at the same a former GUNS columnist. target at 200 yards, the Perhaps because Keith was tip of the bottom post also a good long-range will be 12 squares below target shooter, he was the the crosshairs. This ratio one hunting writer of the of distance-to-reticle period who discussed using (angle) is consistent with a scope’s reticle to estimate range: At 300 yards the range. For pronghorns he distance from crosshairs suggested a scope with to post will subtend 18 two parallel horizontal inches, at 400 yards 24 This big caribou was taken in the days before laser rangefinders with a heart shot crosshairs. They could be inches, at 500 yards 30 at close to 450 yards, by using the scope’s reticle as a rangefinder. used for estimating range, inches, and so on. If we and the lower crosshair know the size of a target we can use this still had plain crosshairs, useless for as a secondary aiming point at longer basic geometric principle to measure reticle range estimation. As a result, distances. range, and even if the target’s size is most hunting “experts,” whether our Here in Montana (and in Keith’s only approximate, we can come up with Uncle Fred or the columnist in our Idaho) a mature pronghorn buck a much closer estimate than simply favorite magazine, suggested various usually measures about 15 inches from “guesstimating.” ways to estimate range. Perhaps the the bottom of the chest to the top of When I started shooting as a little most common was to break the land- the back. This is not around the curve kid in the 1960’s, most hunting scopes scape down into imaginary football of the body, but viewed directly from 12 WWW.GUNSMAGAZINE.COM • AUGUST 2015 fields, because a football field was 100 yards long (They also assumed any redblooded American kid frequented a football field.) Unfortunately, most of the earth isn’t dead-flat and marked off in yardages, but this useless piece of advice showed up repeatedly, apparently because the gunwriters of the day all copied each other (This still happens, but not as blatantly.) Occasionally somebody warned us distances appear different in “clear Western air,” because most gunwriters, along with most people, lived in the East. While it’s possible to get pretty good at estimating distances, I never ran into anybody who did it by imagining football fields. Instead they got good by estimating the distance to a certain object, then measuring or pacing the actual distance to test their guess. This guess-accuracy, however, is normally only possible in pretty flat country, when looking at familiar objects. I became very good at it when guiding pronghorn hunters in the 1980’s, before civilian laser rangefinders appeared, and could usually guess the range to a buck within 25 yards out to 400. But the skill didn’t transfer to mule deer in mountains, and I wouldn’t bet my ability today.