How to Zero a Rifle Scope at 100 yards – Step by Step

If you want accurate aim, one of the most important things to do is zero your rifle scope and 100 yards is one of the most convenient distances to shoot at since it requires minimal measuring, in turn, reducing the chances of you missing.

But while it is important, it isn’t the easiest to do and most beginners struggle with it. Are you one of them?

You are in the right place. I have been working with scopes and rifles for over 5 years now and used 100+ scopes and today I am going to tell you all that you need to know about zeroing your rifle scope at 100 yards like a pro.

So let’s get into it.

How to Zero a Rifle Scope at 100 yards the Right Way

The scope should be mounted correctly

The first thing to make sure is that you have mounted your scope correctly. A few things to keep in mind when mounting a scope includes not over tightening the screws. I know the urge to do so because you want everything in place but it can hamper performance.

Another to keep in mind is that you avoid using Red Loctite as these are harder to remove in case any screw needs readjustment. Instead, go with a thread locker. This is the best way to ensure there are no wiggle or wobbles while leaving room for adjustment later.

The next thing to do is focus the reticle correctly (because nobody wants a blurred dot or crosshairs when you look through the scope, right?) One of the easiest tricks for this is to aim the scope at a single color background. Look away, back through the scope, and away again.

Why so quickly?

Because you do not want to give your eyes the time to focus on the reticle as it may reduce the blurriness. 

So, was the reticle sharp and clear? If yes, you are good to go but if not, turn the diopter. You will find this at the end of the scope near you. Make adjustments till the reticle is spot on.

You also want to adjust the eye relief correctly so there is no dark halo.

In case you are having trouble mounting, here’s a step by step guide on how to mount a rifle scope the right way.

Boresighting

I already talked about bore sighting in my post on How to Sight in a Red Dot Scope Without Shooting but to give you a brief idea, it is aligning the bore of the gun with the sight. Here’s how to go about it.

Firstly, make sure the rifle is empty and nothing is obstructing the barrel. Detach the bolt and rest the rifle on a low but stable platform. I prefer sandbags for the job but you can also use a table, rifle rest, or other solid but stable platforms.

Continue to move the rifle while looking through the bore till the target isn’t in the exact center. 

The next step is to center the reticle onto the same target but make sure the rifle remains unmoved. So how do you adjust it? Well, using the turrets on the scope. Top turrets will move the reticle upwards or downwards (elevation) whereas the ones on the side adjust the windage i.e. left and right adjustment.

If the boresight is slightly off, no worries. Just make sure it isn’t too far off though.

In case you are a newbie and are having trouble with the bore adjustment, getting a laser bore sighter would be ideal. These are installed into the chamber of the rifle and while the goal is still to get the reticle dot center of the target, with a laser, the task is way easier and quicker. 

Not sure which laser bore sighter to get? My favorite is the LaserLyte Universal Laser Boresight. It works with almost any rifle, costs less than $100, mounts in quick-time, and is bright so you can easily spot it in low light as well.

On a tight budget? You should consider the EZ Shoot Laser bore sighter as it costs less than $35. It turns on in seconds with the push of a button and though cheap has a good battery life ensuring you won’t have to worry about carrying batteries or replacing them every few hours.

Getting on the paper

Once the sighting is complete, your rifle is ready to get kicking but there’s one thing a lot of the newbies get wrong i.e. not using the same ammo used during the sighting. That is because every rifle reacts differently to the various ammo and if you want to be 100% certain about the settings and accuracy, do not change the ammo. 

Start with 25 yards as it would be easy to test the setting and then adjust the scope for ranges between 100 yards to 500 yards. Not only will you save on ammo you’d otherwise waste testing straight at 100 yards out but it also makes the process quicker. 

I use bull’s eye targets but some prefer dedicated zero targets with a grid format. For starters, these targets are ideal as the grids make adjustments easier but, in the end, use whatever floats your boat.

When you are out hunting or practicing, stability of the rifle is important. The easiest solution is sandbags and I vouch for them after using them for years. In case you are ready to spend a few extra bucks, there are dedicated rifle rests also available on Amazon and other stores.

Caldwell is one of the most popular brands when it comes to these rests and their Zeromax Adjustable Ambidextrous Rifle Rest is worth the consideration. It costs less than $35 and works with both rifles and shotguns offering you excellent versatility. It also boasts of a durable build and is easy to adjust.

Never use your muscles as support as you are bound to miss the aim since muscles do not provide the same stability.

Ready to fire? Take 3-4 shots in a row. Do you see bullet marks on the target or did you miss it? If you missed it, no problem, it is normal. 

Just measure the distance of the bullets from the bull’s eye and adjust windage and elevation accordingly. Your scope most likely has ¼ MOA adjustment, right? That means every adjustment moves the bullet ¼-inches at 100 yards. 

Once adjusted, take 3-4 shots again in a row. Continue to make adjustments until you hit the bull’s eye with most of your shots. If you are using a high-end scope, the turrets will have numbered markings along with a good click sound for precise adjustments. The turrets should also be smooth so adjusting them takes minimal effort. 

The one thing I like doing is always going a few clicks up. For example, rather than 15 I’d go 18 and bring it back to 15. Another sign of good turrets is their ability to hold a position irrespective of the number of times you mount/detach the scope or move around with it on bumpy terrain. To be doubly sure, just give each turret a gentle tap with a finger so they get locked in. Some of the premium scopes come with special locking features.

Since you might need to test the settings multiple times, give the barrel ample time to cool down, especially if you are using a .300 Win Mag cartridge. That is because, with a heated barrel, the rifle is likely to miss the target. Simply touching the barrel will give you an idea of whether it is too hot or not.

Cooling should take no more than a couple of minutes so the rifle won’t be out of action for long. You can also switch to shaded areas to ensure it doesn’t heat up quickly. 

If you have taken 10-15 shots, you also want to clean the barrel and do this at the range itself and take a few shots after that since you might notice some change in the point of impact. 

Fine Tuning the Scope and Rifle

Well, it is time to take things up a notch by aiming at the designated 100 yards. Since you have adjusted at 25 yards, you should be hitting around the bull’s eye without any adjustment. Just measure the distance from the area and adjust the windage and elevation.

Make sure the windage is spot on (no not even an inch away). As for the elevation, it will come down to the type of cartridge you use. For example, cartridges like  .30-30 Winchester or the .45-70 Govt have trajectories similar to the shape of a rainbow then you want to keep the elevation spot on.

But if not, I’d suggest keeping it about 1-inch to 2-inches higher. That is because it adds to the versatility allowing you to take shots at even 200 yards and yet hitting important areas. 

Once you think the adjustments are made, fire 3-4 shots again. You should hit the target but if not, make the adjustments again.

While it is a good habit to double-check zero before you go hunting or even right before you begin hunting, high-end rifle scopes are much better at maintaining zero even with all the movements, constant mounting/detaching, etc. But that isn’t the case with cheaper scopes, especially if you happen to drop it (don’t tell me you weren’t warned).

A final say.

That’s it, folks. There’s everything you need to do to zero your rifle scope at 100 yards the right way. You can follow these steps for longer distances of 200 to 300 yards as well. 

Remember, practice makes you perfect so even if you aren’t getting any of the steps spot on just yet stick at it. Hunting is a game of patience so settle down, take a deep breath, and then take your shots.

And if you think you need some help at my end, feel free to leave your questions in the comments below. You can even reach out to me via my email or the contact page.