AR Sights & Zeroing Guide

Point of aim vs. point of impact, mechanical offset, sight height, 25-, 36-, 50/200- and 100-yard zeros, iron sights, red dots, LPVOs, prisms, MOA and MRAD adjustments, BDC reticles, magnifiers, tall optic mounts and confirming what the rifle actually does at distance.

Zero   |   Mechanical Offset   |   Trajectory   |   MOA / MRAD   |   Irons   |   BDC   |   Confirmation

Zero is the relationship between the sight line and the bullet's trajectory at a chosen distance.

It is not a property built permanently into the rifle.

Change the ammunition, velocity, sight height, optic, suppressor, barrel or environmental conditions and the trajectory relationship can change.

That's why a zeroing target is the beginning of knowing the rifle—not the end of it.

A ballistic chart predicts the rifle. A confirmed zero proves the rifle.

When a rifle is zeroed at a specific distance, its sighting system has been adjusted so the point of impact matches the intended point of aim at that distance.

Hornady defines zero range as the exact muzzle-to-target distance where the firearm is zeroed and uses that value to calculate the rest of the trajectory.

The bullet still travels according to its ballistic trajectory before and after that point.

On an AR, the optic or sights sit above the bore.

The sights therefore cannot be both physically above the barrel and point along exactly the same line as the bore if the rifle is expected to hit the sight line farther downrange.

Hornady's 4DOF calculator requires the exact height from the center of the optic to the center of the bore.

That's because a 1.42-inch red-dot mount and a 2.26-inch tall mount do not begin with the same sight-line geometry.

Taller optics generally create more mechanical offset at very close distances and can move the ranges where the trajectory crosses the sight line.

When the target is only a few yards away, the projectile has had very little distance to converge with the sight line. So if you're aiming at a small precise point at close range, expect the impact to remain below the sight line by an amount strongly influenced by the rifle's sight height.

You will often hear that an AR bullet “rises” after leaving the muzzle.

Gravity starts acting immediately.

What creates the apparent rise relative to the sight line is that the bore is oriented slightly upward relative to that sight line when the rifle is zeroed.

Hornady describes bullet trajectory in exactly this line-of-sight relationship: changing the firearm's angle of departure changes where the trajectory intersects the line of sight.

With many common AR zero configurations, the bullet starts below the sight line, intersects it once at a closer distance, travels above it for part of the trajectory and then crosses it again farther away as gravity pulls the projectile downward.

That's where names like:

• 25/300
• 50/200
• Other near/far zero descriptions

come from.

Fifty yards may produce a second intersection near 200 yards with one 5.56 load, barrel length and optic height and somewhere different with another. EOTECH's own 50/200-style reticle calibration assumes specific .223/5.56 ballistics. Primary Arms likewise uses different BDC zero relationships for 10.5-, 14.5- and 16-inch 5.56 configurations. Treat the slash as useful shorthand—not a guarantee.

The U.S. military has historically used short-distance zeroing systems that represent a farther battle zero.

Current Army training still uses 25-meter group-and-zero work for M4 training before shooters engage targets at longer ranges.

More importantly, Army marksmanship discussion specifically points out that a 25-meter zero does not guarantee the intended impact at 300 meters and emphasizes confirmation at actual distance.

That lesson applies far beyond military iron sights.

The 36-yard zero has become popular among AR shooters trying to keep a 5.56 trajectory relatively close to the sight line over a broad practical distance window.

Primary Arms' current zeroing guidance lists the 36-yard zero as one common choice for AR/LPVO configurations alongside the 100-yard zero.

What it does on your rifle still needs to be verified with your barrel length, ammunition and optic height.

A 50-yard zero is extremely common on general-purpose 5.56 ARs with red dots and holographic sights.

EOTECH's current .223/5.56 reticles use the 50-yard zero in several configurations and describe a corresponding farther aiming relationship near 200 yards with their assumed ammunition.

Primary Arms similarly uses a 50/200 relationship in certain 5.56 BDC configurations while using different zeros for different barrel lengths and reticles.

That's a great demonstration of the rule: zero labels depend on the ballistic system they're attached to.

A 100-yard zero is particularly common on magnified ARs, SPR-style builds, LPVOs and optics with reticles calibrated around that distance.

Its biggest advantage is conceptual simplicity.

Primary Arms notes that a 100-yard zero generally eliminates the need to remember a substantial mid-range hold-under relationship found with some shorter battle zeros: beyond the zero distance, the shooter increasingly deals with drop and holds above the target rather than a trajectory substantially above the sight line.

If the optic's BDC manual specifies 100 yards, use the reticle the way it was designed before inventing your own zero.

A short red-dot carbine, a tall-mounted night-vision rifle and an 18-inch SPR do not have identical geometry or jobs.

Pick the zero based on expected distances, optic/reticle design, ammunition, barrel and sight height. Then map the trajectory.

Different loads can produce different:

• Velocity.
• Trajectory.
• Point of impact.
• Group size.
• BDC agreement.

If the rifle is built around one primary ammunition load, establish and confirm the primary zero with that load.

Zeroing off single shots is a great way to chase normal dispersion around the target.

Use a stable shooting position and establish a repeatable group before deciding how far the sight actually needs to move.

EOTECH's current zeroing procedure uses groups, adjustment, and another confirmation group rather than chasing individual impacts.

Aimpoint likewise recommends a solid support during the zeroing process.

1. Verify the optic / sights are securely mounted.
2. Know the intended zero distance and reticle requirements.
3. Use the ammunition the rifle is actually being zeroed around.
4. Start from a stable supported position.
5. Fire a real group before adjusting.
6. Identify the center of the group—not the prettiest single hole.
7. Calculate the required angular correction.
8. Adjust windage and elevation according to the exact sight's click value.
9. Fire another group and verify.
10. Once zeroed, confirm at the actual intended distance whenever possible.
11. Then shoot intermediate and close distances and record the real holds.

Bore sighting can save ammunition by getting the optic roughly aligned with the bore before the first live-fire group.

EOTECH specifically describes bore sighting as a preliminary step and then directs the user to complete the zero through live-fire range confirmation.

A laser in the bore does not reproduce actual projectile trajectory.

On most modern optics, turret markings tell you which direction an adjustment moves the bullet's point of impact.

If the group is two inches left, you want the point of impact to move right.

Still verify the exact manufacturer's instructions because sight mechanisms are not all identical.

MOA is an angular measurement.

One MOA subtends approximately:

Leupold defines one MOA as approximately 1.047 inches at 100 yards. For fast field math, shooters commonly round that to about one inch.

Common optic adjustments include:

• 1 MOA per click.
• 1/2 MOA per click.
• 1/4 MOA per click.
• 0.1 MRAD per click.

EOTECH, for example, currently uses 0.5 MOA adjustments on many HWS models. Trijicon offers optics with 1/4-MOA adjustments and others with different values. Read the actual sight specification before counting clicks.

A milliradian is another angular measurement.

Trijicon's technical glossary gives the useful conversion:

If your reticle and turrets are both MRAD, you can measure the miss in the reticle and dial that angular correction directly without converting everything into inches first.

MOA reticle with MOA turrets or MRAD reticle with MRAD turrets keeps corrections simple. A miss measured as 0.6 mil can simply be corrected 0.6 mil instead of converting angular systems in the middle of the process.

Traditional AR sights normally divide correction between:

• Front sight: primarily elevation.
• Rear sight: primarily windage, with elevation capability on some systems.

Actual click values vary with sight design and sight radius. Use the instructions for the sight installed on the rifle rather than assuming every AR iron moves the same amount.

Co-witness does not mean the red dot and iron sights become one adjustment system.

Zero the irons.

Zero the optic.

If both are correctly zeroed for the same trajectory relationship, their aiming references should agree appropriately without using one as a substitute for live-fire confirmation of the other.

The previous Optics & Mounting Forge File covered 1.42-, 1.57-, 1.93- and 2.26-inch optic-height families.

As the optic centerline moves higher above the bore, the rifle starts with a larger vertical difference between where the optic looks and where the barrel actually sits.

If you move from a traditional low mount to a tall NV-oriented mount, reconfirm the zero and relearn the close-range offset.

A Bullet Drop Compensating reticle places aiming references at angular positions intended to approximate the trajectory of a particular ballistic setup.

Trijicon states that its BDC reticles are calibrated around specified cartridges, and individual products may further assume particular projectile / velocity relationships.

Primary Arms likewise publishes different ACSS BDC relationships for different calibers, barrel lengths and zero distances.

A BDC is fast because somebody already did ballistic math for an assumed configuration. Your job is to find out how closely your rifle matches that assumption.

If your reticle says “300” and your rifle's actual trajectory puts that aiming mark slightly high or low at 300, the rifle is not broken. The rifle simply does not exactly match every ballistic assumption used to design the reticle. Shoot the distances and record your real data.

If you're using an SFP BDC or ranging reticle, know which magnification makes the markings correct.

EOTECH explicitly states that a magnifier does not need a separate zero because it is magnifying the already-zeroed HWS reticle.

Magnifier windage/elevation adjustments are used to center the reticle in the magnifier's viewing field—not to create a new point of impact.

Zero the primary optic. Align the magnifier sight picture.

Adding muzzle weight and changing barrel dynamics can move point of impact even when the suppressor is correctly mounted.

If the rifle is regularly used both suppressed and unsuppressed, determine whether there is a repeatable point-of-impact shift between the two configurations.

Record it rather than assuming the zero remains identical.

A reduced-distance zero target is a tool.

It can approximate where the projectile should be at a short distance so the rifle will be close at the intended farther zero.

But muzzle velocity, ammunition, sight height, barrel and shooter error all remain real.

Even Army marksmanship discussion emphasizes this exact point: a near-distance zero should be confirmed at the real distance.

Once the rifle is properly zeroed, shoot it at the distances you actually care about.

Record:

• Close mechanical offset.
• 50-yard impact.
• 100-yard impact.
• 200-yard impact.
• Farther holds relevant to the rifle.
• BDC discrepancies.
• Suppressed / unsuppressed shift if applicable.
• Meaningful changes between primary ammunition loads.

That information is more useful than memorizing somebody else's screenshot of a ballistic chart.

• After installing or removing the optic.
• After changing mounts or mount height.
• After significant optic / rifle impact.
• After barrel or upper changes.
• After changing the primary ammunition load.
• After adding a suppressor you intend to use regularly.
• When groups or impacts unexpectedly move.
• Before relying on the rifle after extended storage or major service.

We don't care which zero has the strongest internet fan club.

Pick the zero that fits the rifle, optic and distances. Measure the sight height. Use the ammunition the rifle actually runs. Confirm the zero at distance.

Then learn the holds instead of pretending a two-number label replaced ballistics.

A zero is a geometric and ballistic relationship.

Sight height establishes mechanical offset. Ammunition and velocity establish trajectory. Zero distance determines where you intentionally intersect the sight line. BDC reticles add another set of ballistic assumptions on top.

The target tells you whether all those assumptions were right.

Zero it. Confirm it. Map it. Then stop guessing where the rifle hits.

• Aimpoint — Zeroing Your Red Dot Sight
  Supported zeroing technique, stable shooting position and dedicated targets for 25-, 50- and 100-meter zero work.
• EOTECH — Help Center / Zeroing & Bore Sighting
  Bore-sighting as a preliminary step, live-fire zero completion and parallax considerations during zeroing.
• EOTECH — HWS Reticle Index
  Current .223/5.56 50-yard zero relationships, 200-yard reference behavior and cartridge/velocity assumptions used by specific reticles.
• EOTECH — Magnifiers 101
  Why a magnifier does not require a separate ballistic zero and how its adjustments center the primary reticle in the viewing field.
• Hornady — 4DOF Ballistic Calculator Instructions
  Zero range, sight-height measurement, atmospheric variables and ballistic trajectory inputs.
• Hornady — External Ballistics
  Line of sight, bore / departure angle, trajectory, gravity and how different zero distances change bullet path relative to the sight line.
• Primary Arms — Rifle Zeroing Guide
  Current zero-selection guidance including 36- and 100-yard AR / LPVO approaches and confirmation methodology.
• Primary Arms — Iron-Sight Zeroing
  Point-of-aim / point-of-impact concepts, ammunition consistency and common 25/300- and 50/200-style AR zero strategies.
• Trijicon — Technical Glossary
  MIL/MRAD angular relationships and BDC reticle calibration principles.
• Leupold — Optics Glossary
  Minute-of-angle definition and the 1.047-inch-at-100-yards angular reference.
• U.S. Army — Confirming Zero at Distance
  Why a reduced 25-meter zero does not automatically guarantee the intended 300-meter impact and why confirmation at distance matters.
• Vortex Optics — FFP / SFP & MOA Technical FAQ
  First- vs. second-focal-plane reticle behavior and angular measurement fundamentals.

Research reviewed October 2, 2026. Trajectory depends on cartridge, projectile, velocity, barrel, sight height, atmosphere and zero distance. Published near/far zero relationships should be treated as starting predictions and verified with the actual rifle and ammunition.

IRONKELLS ARMORY | AR FORGE FILES

Zero It. Confirm It. Map It.

The label on the zero is theory. The impacts on the target are the rifle.