If you do a lot of long-range shooting and have a high-power telescopic sight mounted on your rifle, you have probably run into parallax.
The correct definition of parallax involves more science than most people want to deal with. So here is a simpler version that I hope will be of interest and is far more understandable to folks like myself when viewing a target through multiple lenses.
The target's location may be different by a few inches or more than where one thinks they see it when experiencing parallax.
A little demonstration of parallax can be done right now. Put your hand in in front of you, making a "V", with your forefinger and thumb. Through the bottom of the "V," view an object across the room such as a door knob. Focus on the "V." Now shift your focus to the door knob.
Notice how whatever you are not primarily focused on seems to float a bit. Perhaps a dual image appears.
Our eyes are incredible tools and so are high-quality scope lenses. But this bit of inaccuracy could result in a shot that is an inch or more off, resulting in a miss or an inhumane kill, so it must be addressed at the range by the shooter.
Now that you have experienced parallax without a scope, let's look at it using a scope. Make sure your scope is securely mounted to your rifle and is zeroed for you and not some other shooter. Also, make sure the rifle is mounted on a bipod or some other stable object.
Pick a stationary target at a mid-range distance, such as 300 yards. Make sure the picture is clear and in focus as you center the reticle on the target.
Now, keeping the scope perfectly still, move your head, keeping focus on the target. See how the target seems to move around? Repeat this head movement exercise, taking note of whether the reticle stays on target and seems to move with it or whether it remains in the center as the target moves around.
If the center of the reticle remains on target, moving in unison with it, your shots should go where you want them to go. If the reticle and the target separate, you are experiencing parallax.
Many people mistake the left-hand adjustment knob on their rifle scope as a fine tuning knob. It is really there for parallax adjustment.
If your scope has a parallax knob, repeat the parallax test while adjusting the parallax knob until the target and reticle images float as one.
The fine focus adjustment on most rifle scopes is the small ring on the rear of the optic. It is recommended that one secure the ring with electrical tape once fine focus is achieved, preventing unintentional turning of the ring while carrying your rifle in the field.
Smokey Merkley was raised in Idaho and has been hunting since he was 10 years old. He was a member of the faculty of Texas A&M University for 25 years. There he taught orienteering, marksmanship, self-defense, fencing, scuba diving and boxing. He was among the first DPS-certified Texas Concealed Handgun Instructors. He can be contacted at mokeydo41245@hotmail.com.
