How To Zero Your AR15

By Tom McHale

how to zero your AR
Eyesight is straight, while bullet flight paths arc.
Tom McHale headshot low-res square
Tom McHale

USA –-(Ammoland.com)- Today we’re going to do complicated math!! But in the end we will answer that question, how to zero your AR15?

We’ll be talking about AR15s, zeros, trajectories, and gravity.   Fortunately we will not be talking about shooting in zero gravity as bullets would fly forever, or at least until they crash into the drifting hulk of the Discovery One.

Fortunately, it’s not as complicated as deciphering the true meaning of White House press briefings, as long as you understand how bullets fly.

Bullet trajectory is almost as simple as dropping a brick, except the bullet flies forward where a brick just drops towards the ground. When you fire a bullet, there is no magical force that helps it defeat gravity. In fact, if you fire a bullet from your AR type rifle, perfectly parallel to the ground, the bullet you fire will end up hitting the ground at just about the same time as a bullet you let fall from your hand straight down. I say, “just about” only because the earth curves a bit, and the fired bullet will have a smidge farther to fall than the dropped one. It’s that gravity thing we just can’t defeat, no matter what.

No matter how fast a bullet is flying, it’s constantly falling towards the ground. Even bullets fired from those so-called “High-Powered Assault Weapons.” If you look at the path of a bullet, it will always be a downward sloping curve, kind of like congressional approval ratings.

But wait, you say, when I aim right at a target 100 yards away, the bullet hits it! That’s correct, but only because the barrel is actually pointed a little bit upwards relative to the ground. Shooting a bullet is a just like throwing a football except you don’t get 12 million a year plus a signing bonus. You need to aim it up a little bit so it arcs back down to intersect at your desired impact point. (See Bullet Flight Path image above)

Most AR optics are about 2 1/2 inches above the bore line.
Most AR optics are about 2 1/2 inches above the bore line.

Whether you use iron sights or a fancy optic on your AR rifle, you will always need to plan for the intersection of the straight line designated by your line of sight and the arc of the bullet. Your line of sight is not subject to the laws of gravity, so you see in a perfectly straight path, unless you stayed out too late last night. Since your bullet leaves the barrel in an arc pattern, it may actually intersect your line of sight twice – once on the way up, and again on the way down. But that depends on your zero distance.

Think about it. Your sight is already about 2 ½ inches higher than the center of the bore, so the barrel HAS to be aimed up a bit if it ever hopes to intersect with the line of sight.

Zeroing your rifle simply means configuring your sights, iron or optics, so that at some desired distance, your line of sight perfectly intersects the path of the bullet.

If this seems confusing, just think back to the example of throwing a ball. If you throw exactly at the target, the ball will hit the ground before it gets there. Because of gravity. If you arc it up a bit, gravity will bring it back down, and if you calculated right, that would happen right where your teammate is ready to catch it.

There is one more variable to consider and that’s the velocity of your specific bullet fired from your rifle. No matter what the velocity, gravity still rules. A faster bullet will not defy gravity any more effectively, but it will fly farther in the same amount of time, so there is an illusion that it “defies gravity” better than a slower projectile. So, with a faster bullet, those curves we just discussed will appear to be a bit flatter, but that’s just because the bullet travels farther forward in the time it takes to fall to the ground due to the effects of gravity.

Now that the conceptual scientific stuff is out of the way, let’s talk about how to zero your AR 15 rifle.

For purposes of this discussion, we’ll assume that we’re talking about a .223 Remington or 5.56mm caliber rifle, although at shorter distances, it really doesn’t matter as you’ll soon see.

Since the whole idea of zeroing is to line up your sights with the impact point of a bullet, you can set your “zero” just about wherever you want. But first, remember that the sightline is 2 ½ inches (give or take depending on your equipment) above the bore. For purposes of this discussion, our examples will assume we’re using a standard 55 grain .223 Remington cartridge.

  • If you set your zero close, say at 10 yards, you will have to align your sights so that the barrel points up very aggressively relative to the sight line. The barrel has to be angled up pretty severely for the bullet to move up 2 ½ vertically in such a short distance. As a result, after the bullet crosses the 10 yard zero, it will keep traveling upwards. Farther down range, say at 100 yards, the bullet will be 20 inches above your line of sight.
  • If you set your zero at 50 yards, the angles are less severe. The barrel is angled less aggressively towards the line of sight. With a 50 yard zero, your bullet will only be about 1.57 inches above the line of sight at 100 yards and height maxes out just over 2 inches above around 150 yards. From then on, it’s all down hill again.
  • If you set your zero at 100 yards, the bullet slowly arcs up to intersect the line of sight way down range. Coincidentally, with a 100 yard zero, the bullet never really travels above the line of sight. As soon as it intersects the line of sight at 100 yards, it starts the downward fall again.

As you can see, you have some decisions to make depending on how you anticipate shooting. If every single target you will ever shoot will be at the exact same distance, then set your zero for that distance. However, this is kind of unrealistic. Most people will need to be able to hit targets at different ranges, so you need to compromise.

The most common approach to settling zero distance compromises is to think in terms of acceptable impact zone. For example, if your shot impacts within, say, 3 inches above or 3 inches below your point of aim, that might be good enough for the job at hand. If this outcome is desired, then your job is to find the zero that prohibits the bullet from traveling more than 3 inches above the line of sight. At some point down range, the bullet will fall more than 3 inches below your line of sight. That will be your maximum range where you can hit your target “closely enough” without adjusting your aim point.

As an example, let’s look at the 50 yard zero. By definition, the bullet arcs upwards until it reaches the line of sight at 50 yards. It continues traveling above the line of sight until it peaks at 2.1 inches above the sight line about 150 yards down range. Now the bullet obeys gravity and starts to drop. At 300 yards, it’s fallen to about 4.16 inches below the line of sight.

If you’ve been paying attention, you’ll note that the total “vertical range” is only about 6 inches: 2 inches above the line of sight and 4 inches below anywhere from zero to 300 yards. If hitting in a 6 inch circle is good enough, you can aim directly at your target as long as it’s anywhere inside of 300 yards and you’ll get a hit. You might hear this concept called “point blank range.

It just means you don’t have to make any adjustments for targets within that range.

A look at how 25, 50 and 100 yard zeros impact the bullet's flight path.
A look at how 25, 50 and 100 yard zeros impact the bullet’s flight path.

I like to zero my .223 Remington (or 5.56mm) rifles at this 50 yard distance for a couple of reasons.

  • First, it gives me “point blank” aiming capability out to 300 yards, which is getting pretty darn close to the maximum effective range of a .223 Remington / 5.56mm cartridge anyway.
  • Second, most of my optics are in the 1x to 6x magnification range, and I can aim very precisely at the 50 yard target to get a very accurate zero.
  • Third, my eyes are old. I can only actually see targets within 300 yards, even when using a red dot sight with no magnification.

If you choose a shorter zero distance, say 25 yards, you simply have to be aware that you’re firing along a more aggressive arc. Your sight is still about 2.5 inches above the muzzle, so in order for the bullet to meet the aim point at just 25 yards, your rifle is firing upward at a steeper angle. That’s OK as long as you realize that the bullet will travel higher above the sight plane while on its path downrange.

The reverse concept applies if you choose a longer range zero. Between your firing position and your zero point, the bullet will always be within 2.5 inches of your line of sight as it’s still rising to meet the zero point intersection. After the zero point, since the bullet has been in the air longer to get there, it will rapidly fall away and you’ll have to account for how far below your line of sight it is at a given distance.

As you can see, setting the zero on a standard AR rifle is all about compromises that factor in your anticipated target range. I’ve just found that a 50 yard zero allows me the greatest flexibility and simplicity of aim at a wide range of distances.

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About

Tom McHale is the author of the Insanely Practical Guides book series that guides new and experienced shooters alike in a fun, approachable, and practical way. His books are available in print and eBook format on Amazon. You can also find him on Google+, Facebook, Twitter and Pinterest.

  • 44 thoughts on “How To Zero Your AR15

    1. Very good article. I sigh my AR15 at 35 yards. With this I am about 2inches high at 100 yards and 2inches low at 220 yards with a second zero at 145yards this is according to ballistic charts. This works for me.

    2. No, I did not read it.
      The first thing I searched for in this article was the word “WIND”.
      I didn’t find it.
      if its in there, I’m sorry, I should read it again.
      Please correct me if I am wrong.

    3. Phil,

      Are you saying that you need to first “zero” for wind?
      That is what it sounds like you are saying. Distance is easiest to control/anticipate.
      Yes, you need to always be aware of wind/windage adjustments. But with your concern for “wind” missing from this article, it seems that you would be re-zeroing your sights with every wind change.
      Maybe I missed your point.

      1. The AR with a 20″ barrel hits the line of sight at 35yrds and 300yrds. Saw a guy mention he was low at 200yrds after a 35yrd zero. Must have the 16″ barrel. Semper Fi.

      1. Hah, you must be old like a lot of us! :). That said this article makes it a lot easier for new and old shooters alike.

    4. I only have a 100yd range to shoot on, so I was hoping to let someone else do the brainwork. Ar15, EoTech 516, 62gr(2870fps?), 50yd Zero, I’m 2-3″ high at 100. I’ve got four graphs off the internet, and none agree with the FM3-22.9. The Winchester app is closer to what I actually get. Any excuse for another trip to the range.
      But it is really important to see exactly where you are hitting @5, 10, 25yds.. I keep one test target right by my desk to remember.

    5. Your advice is correct, but your technology is wrong. Speed does affect the effects of gravity and gravity does effect the line of sight. It’s just negligible in this case. It’s astrophysics.

    6. Corrections:

      “No matter how fast a bullet is flying, it’s constantly falling towards the ground.”

      False. Not if it is fired at an angle above parallel to the earth. Correctly stated, “No matter how fast a bullet is flying, it’s constantly being pulled earthward by gravity.”

      “But wait, you say, when I aim right at a target 100 yards away, the bullet hits it! That’s correct, but only because the barrel is actually pointed a little bit upwards relative to the ground.”

      Maybe, maybe not. Correctly stated, “But wait, you say, when I aim right at a target 100 yards away, the bullet hits it! That’s correct, but only because the barrel is actually pointed a little bit upwards relative to the line of sight.”

      Simple external ballistics, at least as far as elevation is concerned, focuses on 4 “lines”. “Level line”, which is a straight line from the muzzle to the actual point of impact. “Line of sight”, which is a straight line from the eye to the intended POI. “Bore line” or “Angle of departure”, another straight line defined by the bore axis. And lastly, the actual “Trajectory” which is an arched line.

      There are additional factors which will affect bullet fall other than gravity, but at other than extreme long-range shooting distances they are negligible.

        1. What’s with the hate man? Plus you expect him to read a comment NOW on what he wrote last YEAR? Get a grip & chill a bit eh?

      1. DL: Others have said this far more bluntly. I’ll try and be charitable. How many people do you think read your reply and had an understanding of what you said? Better yet, how many do you believe even cared? The article was to get the concept across to the greatest number of people and give them something that’s easy to remember when they go to the range. They can do none of that with your explanation. THINK before you completely muddy the waters.

    7. Seems Mr. McHale has gone the long way around barn to describe the simple Santose Combat zeroing method which has been around for decades now, something definitely not new and found along with other interesting tidbits of M16/AR15 knowledge at the original source aka “ar15.com” – where the faux experts go to steal their information and make it their own.

    8. Seems Mr. McHale went the long way around the barn to describe the simple Santose Combat zeroing method in use for decades which I’m guessing came from the original M16/AR15 experts aka. “ar15.com” – where faux experts go to steal the facts and make them their own…….

      Guess the editorial process could use some tweaking here at Ammoland or at least someone that recognizes plagiarism when they read it.

    9. Years ago Marlin distributed a table showing both distances where a bullet crossed the line of sight, once on the way up and again on the way down. Very handy for sighting in a rifle for longer distances using short distances. Have looked for one for several years without any luck.

    10. I enjoyed reading this article very much .I have only ever owned normal everyday rifle till I got my own Ar 15 .My combat issue I zero my ar in at25 yards fired 5 rounds got an amazing group moved my ta get out to 50 yards with my new rifle and scope and got a five round group the size of a 1/4 three inches high was ready for pulling my teeth out as I am bald .Anyway today I moved my target out to 150 yards and I am happy as a clam .The thing is I have to buy another scope maybe a red for shooting in my yard o well .I am lazy I have a 300 yards range on the back of my land I am plain lazy .I did go out to 300 and got a 1 1/4 inch group at 300 yards .Brilliant article

      Thank you

    11. Didn’t tell me one thing about how to sight my rifle ..how to move a sight which way it goes and how much . Nothing helpful .. I. Couldn’t care less about the information you gave was not helpful at all. Thanks for my time waisted for reading your misguided title said how to zero a rifle.. nothing.

      1. It was once said ” A NATION OF RIFLEMAN” get your gun zero at 25 yards, move to a hundred yards check point of impact make adjustments , move to 300 yards check point of impact make adjustments if required, you want to be in a kill zone while holding dead on, somewhere their is the magic of your rifle and you, the same process is done all the way out to 500 yards , you will learn know what to do at all ranges but must go shoot.

      2. You probably should NOT own a firearm or fire one, EVER if you do not know how to mount a optic and how to use an optic, let alone a firearm.

      3. Wow Michael, just wow. So just to help you here “how to move a sight which way it goes and how much” refers to “elevation”…Up and Down for you, and “windage”…Left and Right for you. The article was attempting to inform you on an accepted standard for zeroing in your firearm in order to minimize a lot of thinking around what gravity is doing to your shot and where to aim at certain distances. Information published before? Yes. Does that bother me? No. Misguided title? No.

        Please LEARN the language and concepts so you don’t sound like a five year old. Understand the concept so you don’t post stupid statements. Want to learn how to use YOUR specific optic (“move the sight”) on YOUR firearm (the part that fires the bullet)? Read the instructions…That’s not what this article was about.

        1. In the Corps, we zero at 35 yards, once zeroed at 35, you’ll get the same POI at 300 yards. 3-4″ high at 100. Of course slightly low at ranges under 35. Semper Fi.

      4. Hey Mikey – your comment reads like it was written by a retarded 8 year old… I hope that’s not actually your mental capacity, or obviously you should NOT have access to firearms! IF YOU CAN’T FIGURE OUT HOW TO ADJUST SIGHTS, YOU SHOULD NOT BE SHOOTING AT ALL. Be smart, be safe. Read. Get help. Absorb. Think. Learn. Practice with knowledgeable company to assist you.

    12. You just need a ballistics table for the round you are firing. Every bullet manufacturer has such a chart and it shows the curve and where the bullet crossed the arc at close range and at 100 yards. Get a copy of “point blank” software and input your reload info and you can print out a perfect drawing of the arc with footage attached. And it’s free. http://huntingnut.com/index.php?name=PointBlank

    13. Nice article for the fundamental intro it was intended to be.

      I would have simplified it into this : Virtually any centerfire rifle, firing a projectile with an initial muzzle velocity in excess of 2700 fps, zeroed to hit the target approximately 2.5 inches above the center of the bullseye (Point of Aim) will have the aforementioned Minimum Point Blank Range (MPBR) of approximately 300 yards.

      This will, of course, vary from cartridge to cartridge, and by bullet weights as well. But it is rule of thumb that I have used for over 40 years of competition shooting, hunting, and plinking. Within that context fine tuning is of course required for each cartridge to achieve the level of precision desired, for the particular task at hand.

      In summary: with the assistance of a good reloading manual and its included ballistics (for those without a 100yd range) charts, using a 2.5 inch high @ 100 yards sight in, 97% of the shooting public should be able to hit the aforementioned 8 inch pie plate out 250-300 yards. Beyond that it becomes pretty much a moot point because fewer than 10% of most shooters PRACTICE THE NEEDED SKILLS to be able to effectively shoot at those distances. Theory is one thing. Unless you actually practice at longer distances, it makes absolutely ZERO difference what your ZERO is set at. Most shooters would be far, far, better served spending as much or more time at the range as they do engaged in keyboard wars. Not passing judgement, merely passing along a lifetime of range observations.

    14. Thanks for your time putting this together.
      I use it to teach new shooters basic ballistics principals.
      Bill Payne ~ Ponchatoula, Louisiana

    15. I believe you accomplished what you intended – to inform those who didn’t know how to zero in their rifle and needed some easy to understand coaching. VERY well done in that respect.
      Anyone who writes an article, for public consumption, must have, or must develop, a thick skin while not becoming hard hearted.
      Unless you are offering an opinion – which is proven to be wrong/incorrect – move past the neigh Sayers.

    16. At least one of the commentators mentions ballistic calculators, but there is little elaboration given. Basically, these are simple, on line computer programs into which you put your bullet characteristics (weight, muzzle velocity, ballistic coefficient), firearm characteristics (the height of your scope above the barrel), and environmental conditions (temperature, elevation). You then specify your zero distance, and the output will be the height above or below your zero point, velocity, and energy at various range increments that you have specified. You can find generic ballistic calculators or those for the specific bullet or scope and bullet you are using. I use the ones by Hornady (bullet) and Nikon (scope and bullet) for two of my hunting rifles.

      Once you have the calculations, then you can zero your rifle at the range and check it against the calculations. If they are close, you then have the “dope” for shooting at various distances. I make a little table and tape it inside the eyepiece cover on my scope.

      If you want to know about wind, go back to the ballistic calculator that works best for you and input various wind speeds and directions to get a rough idea of windage adjustments. Generally you need only check 5 and 10 knots of wind at 45 and 90 degrees.

    17. I like to use adjusted zero targets for setting zero on my AR.

      Just google ARMA DYNAMICS OPTIC ZERO TARGETS, you can download them no cost,

      great for ranges that are only 50yd, zero at 50yd and you are good for 200yd too.

      Easy to follow instructions on the targets. They have them for AK-47 too.

    18. I used the Candian Bull as I was taught in basic training. The Canadian Bull has a black rectangle with the center bottom notched out. above the rectangle and below the rectangle are “X’s”. AT 25 meters thw rounds are suppose to strike the target at the bottom X. Technically the round is climbing in altitude. further down range the round crosses the LOS (Line of Sight). Somewhere down Range (about 237 meters) The round reaches its highest altitude which is about the location of the X above the rectangle. After that point the round begins to drop off in altitude because the velocity drops off. But at a range of 300 meters the round is still effective, and possibly up to 400 meters. The target is not the center knotch. This is only the LOS. If you set the target so that the notch is at center of mass, the area between the top and bottom X’s will show that you can hit vital organs at just about any range from 25 to 300 meters distance.

    19. Old guy here.

      I’ve used the MPBR of 25 to 35 yards for ALL of my scopes magnified and simple red dots since about 1980. I still read the article and it reaffirmed how I and my friends have initially zero’ed all 22-250, 7MM Mag, .308 and 5.56 or .223 rifles. I am retired but used to shoot with former marine or police snipers on occasion.

      Each scope has a manual for beginners on how to change windage and elevation. Learn about MOA, MPBR Parallax and why they matter. The marine snipers manual is helpful to newbies for terms and methods. Keep a log book to aid your shooting memory. Speer’s reloading manual has always included comments on zero and elevation for down hill and wind effects and bu8llet type or load. Speer’s reloading software includes a great ballistics chart.

      Some handy items? A 1000 yard range finder, a chrony chronograph, a GOOD 50 power spotting scope, any good reloading manual, a reloading machine and proper precision tools/components. Personally we used a properly built and sighted M1 or M1A with mil spec ammo to judge distance out in the wild for targets

      Note a Russian who shot with us routinely zero’ed his rifles at 300 met3rs MPBR and told us that is the Russian practice for AK-47s. He noted a proper AK or SKS iron sight will have that prepared and ready to confirm on the range..

    20. So if the 25 yard zero hits at 400 yards again, why would you not do a 25 yard zero if the rise is only 6 inches? Aiming center mass at a man is still a gut or neck shot.

      1. thats pretty much US Army training, the standard is a 25m zero. With a 25m zero, you should be able to hit man sized targets with iron sights out to 300m

    21. In 1962 I was at Fort Dix , NJ. We were taught to use Battle Sight Zero. We zeroed at 29 yards with the M1 . This was zero at 200 yards. We fired at siloutes at distances of 50 yards To 600 yards on the same course. Not known distances because in battle you don’t change your sights for different yardage. You use Kentucky Windage for firing at the different yardage.

    22. Thanks so much in 60s i was at fort Jackson but had been so long have for got lot i am old but times are coming that will be lot harder and getting ready as can stay safe.

    23. This article has been very well written. Simple language and concepts that even Jarheads can understand, which is why Marines are the finest marksmen in the world. (Semper Fi).

    24. Hi there,
      You’ re writing about zeroing but what you describe is not really zeroing. You are just sighting at a given distance. without any correction. This way, 50 yards will give you something not very far from a true zeroing. At 25 yards you will be zeroing only if your bullet hit the target 1″ more or less Under your aiming point. this will give you a good aiming from 25 to about 225 yards, just like sighting point blank at 50 meters.
      What is interesting in being able to zero at 25 yards is when you just have access to a short shooting range.
      But your article was interesting by itself.
      Sincerely yours,
      Marc

    25. You can ring steel at 600 meters with a 16″ barrel in 5.56N. I’m fairly certain it would kill at that distance, especially the heavier projectiles in a 1/7″ rate barrel. If the target was static it would take a hit. I see claims that 450 yards is a magic effective range, and it’s just not true. It’s a misconception. The effective range of a 14.5″ 1/7 5.56 in 62g projectile in M4 is 500 meters. That’s approx 546 yards.

    26. It is interesting that this article leaves out three very important items, bullet weight, bulled CD (cross-sectional density) and speed (muzzle velocity). Speed (Muzzle Velocity) is a result of bullet weight, powder weight, primer, and barrel length–yup, longer barrel means changes in amounts of powder burned and net pressure utilization (my term for when the powder charge stopped creating pressure) which requires matching your load to barrel length.
      When I was in RVN the Gunny told us to sight at 25 yards and we’d be on at 250 yards. We did and we were, using the M16A1 in 1970-71. Of course, when I traded my M16A1 for an M14 with a Starlite Scope on it, that information went out the window and the zero for that rifle was 300 yards. I don’t remember the load or the two points at which the projectile crossed LOS, but everything after 300 yards was downhill.
      My point is that there is a lot of variables not in this article that you need to pay attention to when you go out to sight in your AR-15 or AR-10. That said, this is a very good article and talks about stuff in a way that most people who don’t understand ballistics can readily understand. Remember folks, ballistics is a part of physics, a very exacting science and even heuristics (rules of thumb) need to have parameters.

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