How Rifle Scopes Work

Sighting-in a Rifle Scope

Eye relief
Eye relief refers to the distance from a shooter's eye to the scope's eyepiece.
Martin Lovatt/iStockphoto

The process of aligning a scope­ is called sighting-in. It takes time and patience to sight-in a scope properly. But all that time and effort will pay off when you can fire at a target and have confidence that your shot will be true.

Does your rifle have a lot of recoil? If so, you need to be sure you have enough eye relief. That's the space between the end of the scope and your eye. Eye relief is usually more of a concern when firing a handgun or shotgun, but it's something to keep in mind.


Tighten the screws on the mounting rings so that your scope is secure in the mount. Take turns tightening each side of the rings in short increments. You want to make sure the gap between the top and bottom halves of the mounting rings is the same on all sides.

­Find a location where you can set up a target 100 yards (91.4 meters) away from your position. Bring different kinds of ammunition with you -- make sure your rifle can fire each type of ammunition. While most rifles can fire a range of ammo, no two kinds of ammunition will fire in exactly the same way. You need to find out which ammunition works best for your rifle.

You'll need to install the bore sighter in the muzzle again. Try to line up your scope's reticle with the reticle on the bore sighter. If the two crosshairs don't align exactly, you'll need to adjust your scope's settings until they do. This is where the windage and elevation controls come in to play. Tweak the controls until the crosshairs overlap exactly.

The next step is critically important: Remove the bore sighter from your rifle's muzzle. If you load and fire your rifle with the bore sighter still in place, you will damage your rifle and risk serious injury. After you remove the bore sighter, load a cartridge into your rifle. Take aim at the center of your target and fire. Check your target and see if your shot made contact. Don't worry if you didn't hit the target dead center just yet.

Now load your rifle, take aim at the target again and fire off a few shots using one of the types of ammo you've brought. Make a note of where your shots group on the target. Switch to a different kind of ammo and repeat this process. If your shots with one type of ammo are closer to the center of the target than the other, you know which ammo you should use in the future.

Now you can fine-tune your scope's settings so that your shots hit just above the center of the target. This will ensure that you'll be able to hit a target whether it's at close range or hundreds of yards away. Congratulations, you've just sighted in your rifle's scope!

Remember to do your homework before you buy and mount a scope to your rifle. Keep in mind the kind of shooting you'll be doing, the environment you'll be in and the budget you have to spend on a scope. And always remember that it's better to splurge a little on your scope purchase -- it's an investment that will save you frustration in the long run.

To learn more about rifle scopes and related articles, take aim at the links below.

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More Great Links


  • Barnes, Glen. "Scope mounting and sighting in: here's how to do it right the first time." Guns Magazine. Sept. 2003. (Nov. 10, 2008)
  • BinocularsDirect. "How to Sight In Your Rifle Scope." 2008. (Nov. 10, 2008)
  • Brown, Eben. "How to Choose Telescopic Sights for Rifles and Handguns." E. Arthur Brown Company. (Nov. 11, 2008)
  • Double Gun Shop. "Blue Book of Gun Values - Glossary." April 29, 2008. (Nov. 10, 2008)
  • Hawks, Chuck. "Choosing the Right Sight." 2003. (Nov. 11, 2008)
  • Ledin, Steven K. "Scope Mounts and Mounting." RifleScopeBlog. May 28, 2008. (Nov. 12, 2008)
  • OpticsPlanet. "How to Choose a Riflescope." (Nov. 10, 2008)
  • OpticsPlanet. "Importance of a Secure Rifle Scope Mounting System." (Nov. 11, 2008)
  • Staubus, Kent. "Rifle Scopes." AllExperts. Feb. 10, 2004. (Nov. 10, 2008)
  • The Rifle Scope Store. "How to Choose a Rifle Scope." 2006. (Nov. 11, 2008)