The trigonometry of sighting in your hunting rifle


By Trey Spaulding
The first Colorado elk rifle season begins Saturday, Oct. 12, and the first combined deer/elk season starts Saturday, Oct. 19. If you are planning to hunt big game this fall you have hopefully taken your rifle out to the range to practice and to sight it in. Too often, I hear someone say, “My gun was sighted in last year, so I don’t need to sight it in this year.” Or I hear a hunter say, “I went to the range and I hit a paper plate three times at 100 yards…I am ready to hunt.” Nothing could be further from the truth.
During my youth, I shot rifles competitively and I won many state and national championships.  I even held a couple of national records for a short period of time. I would not have won these awards if I had not practiced extensively and sighted in my gun as close to “dead center” as possible.
When you sight in your rifle you should use a bench rest. Before each shot you should relax, take a deep breath, let half of your breath out and hold it, and then squeeze the trigger. Before each shot you should also make sure that the butt plate of the rifle sits in your shoulder “pocket” in the same place as the previous shot. You should not be satisfied that you are sighted in until you have a three shot group that is dead center with each shot touching, or at least a three shot group that can be covered with a half dollar coin.
Here is why?  When you are at the range you have a level and steady rest, adrenaline is not pumping, and you are not trying to catch your breath after just climbing a mountain. When you are in the field, you have these factors and more that will influence the accuracy of your shot. (See diagram). If you are happy that your shot hit 3 inches to the right of center at 100 yards you need to review your basic trigonometry class. At 100 yards, from a steady rest at the range, you hit the target 3 inches to the right of the bullseye. With all of these factors staying the same; if you were to shoot at a target/animal at 200 yards your shot will be 6 inches to the right, and at 300 yards, your shot will be 9 inches to the right. It’s basic trigonometry that needs to be corrected so you do not miss, or worse wound, an animal.
So please take the time, make the investment, and shoot a box or two of ammunition through your rifle to get it “dialed in.” Because when that 300 class bull steps out in front of you at 200 yards and you are experiencing “bull fever” you don’t want to have the disadvantage of your rifle shooting 6 inches to the right because it was not sighted in correctly.

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