How to Zero a Rifle Scope at 100 Yards?

No matter the style or size of your rifle, there is an excellent choice of rifle scopes out there. Therefore, you are sure to find one to fit your shooting style as well as your budget.

With that choice made and the scope in hand, you will be keen to get out there and see if it lives up to expectations. That is certainly the way to go, but before you do, there is one piece of housekeeping you need to put in place. That is understanding how to zero a rifle scope at 100 yards.

This is not as daunting a task as you may think. The benefits of correctly zeroing your scope make this a procedure that all shooters should familiarize themselves with.

So, let’s take a look at this essential process and dig into the “why, what’s needed, and how to.” Once completed, accuracy and precision will be your constant aim!

how to zero a rifle scope at 100 yards

Why Bother Zeroing in Your Rifle Scope?

Before getting started, it should be made clear that ‘zeroing-in’ is often referred to as ‘sighting-in.’ Both terms refer to the same thing and will be mixed and matched throughout the piece.

As for the meaning of zeroing- or sighting-in, this is the process used to adjust your rifle scope in order to hit a target at a specific range.

The main reason to zero in your rifle scope is to achieve consistent accuracy. This accuracy is based on using the same type of cartridge/load to sight-in as you intend to use during your regular shooting sessions.

But, this is not the only benefit of correctly zeroing in…

Because you know your scope is correctly zeroed and accurate at the specified distance, it will help to highlight any shooting technique issues you have. Once these are identified, you can work on correcting them.

Your confidence will increase as regular shots are placed accurately. This consistency will then continually breed even more confidence and up your shooting expertise. Another important factor comes with the ability to increase the distances you are shooting over. This can be built up gradually and will determine the farthest distance you are consistently accurate at.

Why Choose 100 Yards to Zero Your Rifle Scope?

Although this article is concentrating on the best way of zeroing a rifle scope at 100 yards, you can zero-in at any distance. The process is the same, just the target distance varies. Having said this, 100 yards is by far the most popular distance.

It is an acceptable distance to verify alignment between your scope and the bore of your rifle. 100 yards lends itself to a variety of different shooting applications as many shooters target this distance. It can also be looked on as a springboard for those looking to up their longer distance shooting game.

Gaining confidence and consistent accuracy at 100 yards will encourage many to take their distance game further.

Riflescope manufacturers also see the popularity of this shooting distance. There are lots of different scope models out there that have the parallax adjustment set at 100 yards. If this applies to your scope, zeroing in at the same distance makes good sense.

But I Intend Shooting Well Beyond 100 Yards?

Sighting-in at 100 yards is certainly not for everyone. A good example relates to experienced hunters who have their sights set on targeting prey much further afield. This means they will zero in their weapons at far greater distances.

A broad-brush comparison of hunting distances shows that many hunters are consistently accurate at around the 200-yard mark. This means it makes far more sense to zero-in at that distance than having a 100 yard zero.

The thing to remember here is that your sighting-in distance is a moveable feast. You will know your accuracy and distance capabilities and should zero-in to that. Change caliber/load, re-zero-in. At the start of the hunting season and before each hunt, zero-in.

Ammo Used & Logging Shot Detail

Regardless of your chosen zeroing-in distance, there are two things that must always be remembered…

The first relates to cartridge type and load. The type of ammo you use is a personal choice, and that is absolutely fine. But, it is really important to use the same ammo for zeroing-in your scope as you intend to use during future shooting sessions.

This is because to achieve accuracy; you need ammo consistency. The cartridges used for sighting-in will be a particular brand. They will have a specific bullet shape, weight, and load. Jumping from one cartridge type to another is likely to change these variables. If so, it will affect your original zero and mean that your scope and rifle will no longer be correctly aligned.

Tables and charts…

To counter these changes, you can compensate by using bullet-trajectory tables and charts or ballistic programs. While this is the case, it is also true that the zeroing process is not an onerous task. It doesn’t take long to complete, and the more often you zero in, the more familiar the procedure will become.

The second important task needs to become part of every shooting session. You need to get into the habit of logging shooting stats. Firearms enthusiasts are never slow on the uptake and have coined an easy to remember acronym for this: DOPE – “Data On Previous Engagements.”

Examples of what you need to log are the location, ammo load, shot distances, wind conditions, humidity, and scope settings. You should also note the angle of the shot and any other details that are useful. By doing so and referring to this past information, it will help your future shooting game no end.

Be Prepared!

There are various ways of zeroing your rifle scope at 100 yards. I will, therefore, take you through a quick and efficient method that covers preparation, equipment needed, and shot requirements.

Let’s start with the obvious….

Yes, that is your rifle scope! This should be correctly installed on your rifle. Take time over this. You need to read and follow the installation instructions carefully. It is also very important that the mount, rings, and any bolts or screws are tightened to the correct torque. Positioning also needs to be spot-on as this will impact eye relief.

Correct install really is crucial. Having the best scope money can buy will mean very little if it is not correctly attached to your rifle. The result will be disappointment through substandard performance. As for stated eye relief, this will likely be one of the factors that swayed you towards your chosen scope.

It is clear that different rifles loaded with different cartridges will produce recoil that ranges from mild to harsh. If your rifle and load is on the harsh end of the recoil scale, sufficient eye relief is a must. If not, you will be increasing the chance of eye or facial injury each time a shot is taken.

how to zero a rifle scope at 100 yard

Your next step should be a boresight…

This needs completing before the zeroing-in shot process begins. This can be done either manually or using a laser bore sight tool. Bore sighting is straightforward and is not a lengthy procedure. The goal is to ensure that the center of your rifle barrel (bore) aligns with the scope’s sight.

A boresighter device is an accessory that will ease the sighting-in process. They come in two styles; laser or magnetic. Using either type will save time and ammunition. Having said that, such a device is certainly not mandatory. Many shooters manually bore sight and do so with ease.

A quality recommendation is the StrongTools BoreSighter for 223/9MM/7.62X39MM/30-30/30-06/.25/270/243/308/7MM/ 45 Colt Caliber Rifle Scope Handgun Brass Red Dot Boresight Kit.

Also, getting hold of the RUB1ZR0 Boresighter Kit Precision Alignment Bore Sighter with 16 Pieces Adjustable Arbors is an excellent option if you’re looking for pinpoint accuracy.

Next comes the ammunition you will use…

This has already been covered in detail under the “Ammo used and logging shot detail” section. However, the bottom line is that whatever brand and caliber of cartridge you intend to use on a regular basis should be the type you use for zeroing in your rifle scope.

A rifle rest (or a vise) is needed to ensure your gun remains completely stable during the zeroing process.

You also need to have a target set up at 100 yards. Use an easy to see target. Some come with bright-colored, large bullseyes; others have marks showing the distances from the bullseye. The latter type can certainly make your calculations easier. The Remington Bullseye Style 100 Yard Sight-In Target (Pack of 12) is an excellent choice and well worthy of consideration.

The final thing recommended is a pen and paper; obviously, any pen will do, but the 50 BMG Real Authentic Brass Casing Refillable Twist Pen – Tactical Gift Box will certainly impress your friends down on the range. Or for something a little more subtle, how about the NEJLSD Tactical Pen Defensive Tool, Aircraft Aluminum Material Self-defense Weapon. This will allow you to jot down calculations and other relevant information.

Setting Up and Scope Check?

Ensure your target is in position. Then place your rifle with scope securely attached on the shooting rest and pointing at the target. If you are using an alternative ‘rest,’ make sure your rifle does not move while shooting.

Looking through the scope, you need to see a crisp, sharp, and clearly defined target image. Check and adjust such things as the magnification level. This needs to be set to the correct range.

If you have a variable magnification scope, you should be aware of what distances each power setting gives. Then carry out any windage and elevation adjustments. This may be simply fine-tuning, but adjust as necessary in order to have the scope reticle pointing dead-on the target center.

Fire Your First Shot or Shots

When you are satisfied that the crosshair of the reticle is level with the bullseye of the target, fire one round only, then check the target to see where it has hit. This is known as the POI (Point Of Impact). It will be this position that determines whether any scope adjustment is required and by how much.

While just one shot can be used for this exercise, many shooters recommend taking three shots. The reasoning behind taking a group of shots is that it will give a better idea of consistent shot placement.

If you do go for a group of three shots, they should not be fired in rapid succession. The form should be: One shot, check POI. Keep your rifle and scope in exactly the same position and do the same for shots two and three.

A close group of three shots landing in the bullseye is what you are after. However, it is more important that these three shots actually land somewhere on the target and are closely grouped. The reason for this is that a tight group gives you a clear indication that shooting is consistent and the rifle was kept steady.

Assessing your POI

Examining where your shot or group of shots actually landed on the target is your next step. This assessment will tell you what scope adjustments are needed to ensure that your next shot or group of three shots lands in the bullseye. Continue adjusting and shooting as described until you hit the bullseye.

Most U.S. shooters favor scopes that offer adjustments in MOA (Minute Of Angle), although MIL DOT scopes are gaining favor in some quarters. For the sake of understanding how to zero a scope at 100 yards, MOA measurements will be used.

All are not equal…

The first thing to understand is that not all MOA click steps are equal! There is good reasoning behind this, as different click step measurements suit certain shooting applications better than others. Because of this, you will find that manufacturers design different scope models with different MOA click step values.

For example, those into target shooting and precision shooting generally use 1/8-inch MOA clicks. 1/4-inch MOA is popular with hunters, while other rifle users prefer 1/2-inch MOA.

Note:

If you use a MIL DOT scope (often called an MRAD scope), adjustments are more straightforward. These come in 1/10ths.

Adjustments are calculated based on the POI position and distance from the target center. Before giving some calculation examples, here is an easy way to remember exactly what MOA really means:

The MINUTE = Inches – The ANGLE = Yards. The further you are away, the greater the angle.

Calculating MOA Adjustments

Let’s use the three common MOA click steps just mentioned: 1/8-inch, 1/4-inch, and 1/2-inch. To get you in the groove, the same POI shot position and distance from the target center will be used.

Your shot lands 2-inches below and 3-inches to the left of the bullseye. Counting your 1/8-inch MOA click adjustment steps means there are 8 click steps per inch. This means you would have to adjust your aim by 16 MOA click steps up, and 24 MOA click steps to the right.

Using 1/4-inch MOA click adjustment steps means there are 4 click steps per inch. This means you would have to adjust your aim by 8 MOA clicks up, and 12 MOA clicks to the right.

Using 1/2-inch MOA click adjustment steps means there are 2 click steps per inch. This means you should adjust your aim by 4 MOA clicks up, and 6 MOA clicks to the right.

The Final Step

Once your scope has been adjusted, it is time to try another shot. If your calculations were correct and the right adjustments have been made, your shot accuracy will improve. If you are still off the target center, continue to make finer adjustments and take another shot. Once you hit the target center, you have zeroed your rifle scope at 100 yards.

There is also a “belt and braces” last check that many shooters carry out. Let your rifle barrel cool completely, then take one final shot. This will conclusively prove that your sighting-in exercise has been successful.

You are then ready to get out there and improve your shooting accuracy over 100 yards. The best way to do this may be old fashioned, but it is certainly effective. That is to practice, practice, practice!

Looking for a New Rifle Scope to Zero?

Then check out my comprehensive reviews of the Best AR15 Carry Handle Scopes, the Best Air Rifle Scopes, the Best Low Light Rifle Scope, the Best Rimfire Scopes, the Best Mini 14 Ranch Rifles, or Best Scopes for M&P 15-22 on the market in 2022.

Or, take a look at our comprehensive reviews of the Best 308 Rifles Scopes, the Best Deer Hunting Scopes, the Best Scopes for AR15 under 100 Dollars, the Best Mil Dot Scopes, the Best Scout Scopes, as well as the Best 300 Win Mag Scopes you can buy.

Final Thoughts

Understanding the best way to zero a rifle scope over 100 yards is not as daunting as it may initially seem. It is also something that shooters of all levels should learn to do. As mentioned, the 100 yard distance is not set in stone; however, this has become far and away the most popular range to achieve accurate sighting in.

Having your rifle and scope combo correctly set up and zeroed-in should show positive accuracy results. It will breed confidence and help you to become proficient at this distance.

There is no doubt that consistent accuracy is something all shooters want. 100 yards is a distance that many initially aim for. Achieving it with a correctly sighted-in scope will do wonders for your shooting confidence. It will also leave you with a real sense of achievement!

Happy, safe, and accurate shooting.

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About Wayne Fletcher

Wayne is a 58 year old, very happily married father of two, now living in Northern California. He served our country for over ten years as a Mission Support Team Chief and weapons specialist in the Air Force. Starting off in the Lackland AFB, Texas boot camp, he progressed up the ranks until completing his final advanced technical training in Altus AFB, Oklahoma.

He has traveled extensively around the world, both with the Air Force and for pleasure.

Wayne was awarded the Air Force Commendation Medal, First Oak Leaf Cluster (second award), for his role during Project Urgent Fury, the rescue mission in Grenada. He has also been awarded Master Aviator Wings, the Armed Forces Expeditionary Medal, and the Combat Crew Badge.

He loves writing and telling his stories, and not only about firearms, but he also writes for a number of travel websites.

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