How to Zero a Scope: A Basic Guide

Hunting season is upon us, and if you haven’t zeroed your rifle yet, you better get on it. It’s always a good idea to re-zero every year, and many folks will be using new rifles, new scopes, or both. With that in mind, especially with all the new gun owners out there, here’s a basic guide to zeroing your scope. Be warned, zeroing uncovers several rabbit holes in which to lose yourself. You’re free to do that, but this article just hits the basics. We will, however, point you toward those deeper concepts if you’re so inclined.

zeroing a scope
Proper zeroing is crucial to accurate shooting. (Mike Searson Photo)

Mount Your Scope Properly

Properly mounting your rifle scope may seem a little too basic, but it’s fundamentally important. Proper leveling and alignment are obvious, but the mounting screws must be tightened according to the manufacturer’s instructions. Over- or under-tightening those screws will negatively impact the scope’s ability to hold zero and will eventually damage your optic. And even cheap scopes aren’t exactly “cheap.” A torque wrench will get you on target here.

If you aren’t sure how to do it yourself or don’t have the proper tools, many gun stores will mount the scope for you. But you’ll still want to be certain they do it correctly. Take it to someone you trust.

Select Your Distance and Your Load

The distance at which you zero your scope should account for your rifle’s purpose and what ammunition you’re using. My deer rifle, for example, is a Marlin 336 chambered in .35 Remington. I zero it at 100 yards. My hunting range and rifle choice mean I’ll rarely take a shot past that distance.

My AR-15, chambered in 5.56 NATO, is zeroed at 50 yards, which accounts for that round’s performance coupled with the rifle’s projected role. Finally, my 9mm Henry Homesteader Carbine is zeroed at 85 yards, again, accounting for that cartridge’s capabilities and the rifle’s job as I see it. But let’s keep it simple and stay at 100 yards.

.25 MOA rifle scope adjustment turret
This Vortex Strike Eagle adjusts in 1/4 MOA increments. (Author’s Photo)

You should also understand that you’re zeroing for a particular ammunition load. For my Marlin 336, I hunt with the Hornady 200-grain FTX LEVERevolution cartridge. When I zero my rifle each fall, I understand that I’m zeroing for that particular load and nothing else. Each load can and, usually, will perform at least a little differently. Even a theoretically identical load from a different manufacturer.

It boils down to bullets, powders, brass, primers, and other components. Dive into that hole if you want. I might shoot a similar group with something else, but I can’t assume so. I can only be certain by testing that other load. But I know what I hunt with, so there’s no need. The Hornady round delivers consistent performance at my chosen range, to the point that I only have to make minimal adjustments, if any at all.

That consistent performance means I know my holds out to 200 yards if I unexpectedly take such a shot. I’ve taken almost all my deer shooting unsupported, so that small margin of error works well for me.

Finally, I use the 25-yard method of zeroing at 100 yards. It makes it a little easier and probably saves me a few rounds. I know it saves me some frustration, especially with a new scope. I’ll hit that below.

Scope Adjustment and Target Selection

Before zeroing your scope, you should know the units of measurement by which it’s adjusted. Ideally, these units were part of your buying process, but maybe they weren’t. That’s alright, especially if you’re new to this. So long as you know how to use the adjustments, you’re good either way.

Scopes are adjusted one of two ways: Minutes of Angle (MOA) or Milliradians (MRAD or Mils). Most are MOA. One minute of angle equals 1 inch at 100 yards. 1 Mil equals 3.6 inches at the same distance.

MRAD scope adjustment turrets
This MRAD ZeroTech scope adjusts in .1 Mil increments. (Author’s Photo)

Your scope is adjusted for elevation and windage at certain values. The most common are ¼ MOA, ½ MOA, 1 MOA, and .1 Mil. The differences between and merits of MOA and MRAD are yet another rabbit hole if you want to pursue it. Not being mathematically inclined, nor a precision shooter, I’m not all that interested. Your scope knobs should indicate the unit of measurement. If they don’t, your owner’s manual certainly should.

What you should know for the 100-yard zero is that 1 MOA equals 1 inch on your downrange target. If your scope adjusts at 1 MOA, then 1 click on the adjustment knob equals 1 inch on the target. A ½ MOA scope will need two clicks, while a ¼ MOA scope requires 4 clicks to move the reticle 1 inch on the target. If you choose a 50-yard zero, however, you’ll need to double the number of clicks, since the closer distance means the reticle has to move more to adjust.

Zeroing at 25 yards, which is how I start, means you quadruple the number of clicks for a 100-yard zero. I like the 25-yard zero for new scopes or newly mounted scopes because it’s easier to get my rounds on paper at that distance. And since I know the simple adjustment formula, my zero should still be fairly close once I take the target out to 100 yards. Keep in mind, however, that bullet trajectory means your elevation will almost certainly need adjustment at 100, even if your windage is spot on.

Dedicated MOA targets are easily found. They include a grid of 1-inch squares, making it easy to see how many inches you need to adjust. Knowing how many inches means you also know how many clicks on your scope’s turret dial.

MOA rifle targets
MOA rifle targets are easy to find. Note the inch square grids.

If you’re using an MRAD reticle, you can use the scope itself to adjust. The reticle will be marked in Mils, allowing you to walk in your elevation and windage using those marks. If you’re using a Second Focal Plane (SFP) scope, make certain your magnification is set to maximum. SFP windage adjustment marks and bullet drop compensator measurements are only accurate at full magnification. SFP vs. FFP (First Focal Plane) is another topic into which you can delve if you choose.

Shooting Position

Now that you know how your scope works, you’re ready to zero it. The first thing you need is a firm shooting base, whether it be a bipod, tripod, rifle rest, or a sandbag of some kind. I recommend a sandbag or rifle rest. You do what works best for you. Even though I usually shoot freehand, there’s no way I can get a good zero like that. Consistency demands a solid support. I also recommend zeroing your rifle while sitting at a bench or from the prone position. These positions are stable and will help provide that consistency.

Groups are Important

A common zeroing mistake, especially for beginners, is adjusting the scope after one shot. I did this myself until someone taught me better. Adjusting after a single shot doesn’t allow for variables like improper trigger pull or flinching. You should only adjust after firing a group. Some folks shoot three-round groups and others prefer five.

I like the five-round group because it allows for a flyer, plus I acknowledge that I am not a precision shooter. In my opinion, a five-round group just gives you more data. More data is always good. Here’s the process:

  • Fire five controlled, aimed shots at the bullseye. Keep the same aiming point for all five rounds, no matter where you’re hitting the target. Keeping the same aiming point validates your group. Changing the aiming point means your group is useless data-wise.
  • Determine the center of your group. You can measure or estimate the center, whatever you’re comfortable with. If you have a flyer, or a shot that is clearly caused by a bad trigger pull or whatever, you can disregard it. If your group is nothing but flyers, perhaps consider evaluating your shooting technique. I get that it’s tempting to try saving ammo by adjusting after one round. But I learned that I probably used at least as much ammo trying to do it that way because my data was poor.
  • Adjust your scope from the group’s center point. I like to adjust the elevation first. After dialing in the vertical axis, I then move on to windage. You can do whatever works for you, but I’ve found that trying to do both makes me think too much, and that’s never a good thing.
  • Confirm your zero. Once you dial in on both axes, fire another five-round group to confirm your zero. If you’re using the 25-yard method, this isn’t necessary unless you just want to do it. The 25-yard target’s purpose is to get you close at 100 yards. I don’t shoot the confirmation group until I’m on target at 100 yards. Confirming may require another minor adjustment. You can repeat this until you’re happy with the result.
  • Set your turrets back to zero. Most scopes allow you to loosen the dial and turn it back to zero. That way, if you accidentally move the dial, it’s easy to put it back where you want it. Make certain you properly loosen the dial and go slowly. If the dial clicks, you’re changing the zero. Once it’s done, tighten the dial back down.
Prone shooting position
The prone shooting position is very solid. (Jake Bush Photo)

Accuracy Matters

We all want to hit what we’re shooting at. Obviously. But accuracy is a responsibility too. Safe shooting requires accurate shooting. You’re responsible for every round that you fire, meaning that it’s on you to do everything you can to hit your target. And since we mentioned hunting, accurate shots are a big part of hunting ethically. It’s your responsibility to kill an animal as cleanly as possible. That requires accuracy.

Properly zeroing your sights, whether a rifle scope, red dot, or iron sights, helps ensure you’ll hit whatever you’re shooting at. Proper shooting fundamentals obviously play a big part too. But even fundamentally sound shooters can’t hit with improperly zeroed sights. So, take your time and do it right. You’ll be glad you did.

William "Bucky" Lawson is a self-described "typical Appalachian-American gun enthusiast". He is a military historian specializing in World War II and has written a few things, as he says, "here and there". A featured contributor for Strategy & Tactics, he likes dogs, range time, and a good cigar - preferably with an Old Fashioned that has an extra orange slice.

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