Is Your Carbine’s Zero Wrong?

January 14th, 2024

7 minute read

Pull a new AR out of the case, peer through some sights, and one of the first questions will invariably be “What distance should I zero this stuff at?” I could easily regale you with ballistic charts and simply say that “at x distance you’ll be y inches high and that’s why it’s better than z”, but that would be a little disingenuous.

In this image, you face three targets designed to help you zero your rifle. When shooting with optics or iron sights, you need to understand where your bullet will impact. The angle between the scope and bore matters and greatly impacts where you will want to zero the gun. As your POI changes, so does your point blank range. They say precision shooting is simply applied mathematics and they are not wrong. — How do you zero your carbine? Is it at 25, 50 or 100 yards as shown here? Each has its pros and cons. In this article, the author suggests there may be a better option with the 36 yard zero.

Frankly, I don’t think one zeroing scheme is better than another. However, for practicality’s sake you’ll want a zero that is essentially point-and-shoot within your desired effective range. Whether that’s 100 yards and in or from zero to 300 yards, there are a few viable options from which you can choose.

[Be sure to read our article on how to dope a scope.]

To help keep things on track and provide context, I’m using a SAINT Victor 5.56 rifle with a 16” barrel shooting some flavor of 55- to 62-gr. FMJ bullet at about 3,000 fps in my examples. Currently, this is probably the most common AR configuration going, shooting the most common ammunition available.

In this photo, the author has his AR-15 on a shooting range to determine his POA and POI at various ranges. These change depending on your zero point. A zero at 25 yards is different from a 300 meter zero, for example. When it comes to your go-to 5.56 carbine, you want to be sure of your scope dope and combat zero. — Determining the correct zero for your needs will require some thought as well as some range time. Understanding your point of aim and point of impact is critically important.

However, let’s be honest … in the hands of the average shooter, this combination is probably good for 3 MOA on a good day. Sometimes it may do better, sometimes worse. The overlaid circles in the included illustrations help to visualize what that 3 MOA extreme spread translates to on a target at a given distance to get beyond arbitrary ballistic figures.

[Learn how to use a BDC reticle here.]

25 Yard Zero

Even though I don’t recommend the 25 yard zero, I’m starting here because it is suggested so often, but is also often misrepresented as a 25/300 yard zero. Two minutes and a ballistic calculator will show you this zero creates an arching trajectory that rises about 9” above the line of sight at 200 yards.

Shown is a target used for helping you in zeroing your carbine at 25 yards. When outfitting your carbine, you might like a red dot instead of a magnified optic. Even so, you should take the time to properly zero your sights. Bullet drop isn't terribly important as much as understanding holdover when determining the deviation between aim and impact because of the height over bore. — According to the author, the 25-yard zero is one of the most recommended, and misunderstood, zeros for your carbine.

The problem is that it forces you to have to think when to hold under a certain amount on closer targets and when to hold dead on. In the military, we were told to hold low up to 250 meters and then hold dead on for 300 meters. That’s all well and good when your target is 20″x40″, but it starts to get trickier on smaller targets. I can also tell you from experience that when you’re amped up and the lizard brain takes over, you’ll really only be thinking point and shoot.

[For an additional view on the subject, check out How to Zero in an AR-15.]

36 and 50 Yard Zero

That brings me to these two options, which I’d like to talk about together because they’re pretty similar and do well to exploit the advantages of a practical carbine. Now, the arguments that I’ve read on each of these techniques could put a good, old fashioned Ford vs. Chevy debate to shame.

The author is sighting in a non-magnified reflex sight in this photo. Shown is the author's Springfield SAINT AR-15 rifle with a red dot on a riser. You POI at 200 yards is almost certainly different than at 50 yards no matter where you sight in. — The Springfield Armory SAINT Victor chambered for the 5.56 NATO cartridge was the author’s test platform for this article about zero distances.

Like a lot of those situations, though, the points argued are based on personal bias and the actual differences are pretty minimal. To see for myself how these two zeros stack up, I took two similarly set up rifles to the range, one zeroed to 50 yards and the other zeroed to 36 yards.

This is a target demonstrating the impact locations of M193 55-grain FMJ bullets. As you can see, the 100, 150, and 200 yard impacts are all very close together. From 36 to 250 yards, the impacts are all within a circle that is less than the size of the upper center mass. This makes for a good maximum point blank range in the target shown. — While not as well-known as the 25 yd zero, a 36 yd zero has many benefits for which to recommend it.

For better or worse, the 36 yard zero is basically a hybrid that flattens out the St. Louis Arch of a trajectory the 25 yard zero creates while still providing a decent maximum range. Compared to a 50 yard zero, its peak trajectory is slightly taller, about 4” above line of sight between 150-200 yards.

The author wrung out the 36 yard zero on targets at a variety of ranges, with his 5 to 10 yard target shown here.

With the rifle zeroed at 36 yards, I can reasonably expect to hit a BC-Zone target out to 300 yards without excessive hold-overs. If I need to push out a bit farther, I can just hold level with the shoulder line or top of the target for 350 and 400 yards, respectively. To me, the 36 yard zero makes things about as simple as they can get for a multi-purpose rifle that could be used for range, home defense or duty use.

You can see in this image the impact points for the bullets using a 50yd zero. When you zero your rifles along your needs and within the parameters of your optics - such as a battle zero reticle on an ACOG - you can ensure your projectiles go where you want them. — The author is a fan of the 50 yard zero, due to its flexibility. It offers good precision from 50-200 yards, and it can stretch to 250 while stating in the center mass area.

All that being said, the 50 yard zero continues to be one of my favorite zeroing schemes because it’s versatile, proven and effective. The rifle zeroed at 50 yards shot a little flatter with a max ordinate of just a few inches above the line of sight. This affords me the ability to be a little more precise on smaller targets out to 200-250 yards without hold-overs. If I need to shoot farther than that I can aim at the shoulder line to push out to 300 yards or hold on top of the head for 350. Logistically, it may also be easier for some shooters to get a 50 yard zero since many ranges may not have the facilities available to set up and shoot 36 yards.

As seen in this image, the 36 yard zero is preferred by some shooters as it allows for accurate shot placement over multiple distances due to bullet trajectory and gravity's effect on it. It provides relatively flat trajectory up to around 200 yards, allowing high precision without having to adjust sights or holdover. — Shown above are the author’s results with a 50 (left) and 36 (right) yard zero.

At the range I ran through some drills to work on accuracy and precision. Failure drills were shot at the 10, 7 and 5 yard lines, while the hostage taker was done at the 10 after running to make a button hook turn. In both exercises I didn’t feel I had to work harder to get hits using one zero or the other. So long as I accounted for my height over bore, they both worked about the same.

For all intents and purposes, I don’t think you’re going to be let down or at a severe disadvantage if you choose either one over the other.

This image of hostage and hostage taker targets helps to set up a 36 yard zero. One must first safely secure their firearm in a stable rest or shooting bench. Then aim directly at a target placed exactly 36 yards away. Fire several rounds, then adjust the sight based on where your shots are grouping until they are hitting precisely where you are aiming. — The author also tried out the 36 yard zero with this hostage taker target at 10 yards. All hits were on the criminal.

100 Yard Zero

Zeroing a carbine with open sights or a red dot at 100 yards isn’t intuitive, but the concept has been gaining ground in recent years for certain applications. The chief benefit to using a 100 yard zero is that whether your bullet is going 2,500 fps or 3,000 fps it is the peak trajectory. That means from 0-100 yards you only need to be concerned with your height over bore when shooting a target.

To me this makes the 100 yard zero a perfect choice for a carbine that will be used in close terrain where long shots will be limited. The 300 yard shots are still doable, but as target distances increase you’re going to need to know the specific holds for your set up out to that distance, so it’s important to really know your gun.

This target shows the placement of shots when using a 100yd zero. While Springfield Armory might not specifically recommend an ammunition type for achieving an accurate 36-yard-zero, its generally accepted that consistent accuracy comes from using quality ammunition. Different firearms may also perform better with certain types of ammo, so shooters often experiment to find what works best with their specific firearm. — Less commonly seen is the 100 yard zero, which the author thinks is better for when longer shots are unlikely.

Depending on your sighting system and target size this could end up obscuring your target, so keep that in mind if you plan to use this zero. If you’re concerned about getting a good zero at 100 yards, you can always start at 50, adjusting so that your impacts are about ¾” low, and then confirming at 100 yards. Chances are you’ll be very close, if not dead on.

Closing Thoughts

I can’t tell you which zero distance is the best one; that’s really going to be up to you, your skill level and the set-up of your rifle. If you’ve read all this and still aren’t sure of the answer, start with a 50 yard zero and go from there.

Shown is the author shooting his AR-15 on the range. While many firearms can be used effectively with a 36-yard-zero setup, rifles such as those in Springfield Armory's M1A series or their Saint AR-15 series have been noted by shooters for their accuracy and consistency over various distances when properly sighted-in. — However you zero your carbine, make sure you really wring it out on the range and are familiar with where it hits.

Whichever distance you do zero at, I recommend shooting out to as far as possible so that you know what you, your rifle and your ammunition are capable of doing. I’ll leave you with this tip: if you have astigmatism like I do and your red dot looks wonky, flip up the small rear aperture — it will help focus the dot for a better defined aiming point.

Editor’s Note: Please be sure to check out The Armory Life Forum, where you can comment about our daily articles, as well as just talk guns and gear. Click the “Go To Forum Thread” link below to jump in and discuss this article and much more!

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Ian Kenney

Ian Kenney served as an infantryman in the U.S. Army just after 9/11 and is a veteran of the Global War on Terror. Ian is a life-long firearms enthusiast and competition shooter regularly participating in everything from rimfire to long-range precision matches. When not shooting or writing about shooting, Ian enjoys bushcrafting and hiking in the woods of Virginia.