How to Zero a Rifle Scope at 100 Yards: Practical Step-by-Step Guide

Prepare the Rifle, Scope, and Ammunition

Before cleaning or inspecting a firearm, unload it, remove the magazine, lock the action open, and visually and physically check that the chamber is empty. Once that check is complete, inspect the scope base, rings, and mounting hardware. Follow the rifle, mount, and optic manufacturers’ torque specifications rather than estimating tightness. Confirm that the scope has suitable eye relief, the reticle appears level, and the reticle focus is clear.

A laser or manufacturer-approved bore-sighting method can reduce the correction needed to reach the target. Bore-sighting is only a preliminary alignment; the rifle is not zeroed until its point of impact has been confirmed with the intended ammunition.

Choose one load for the entire zeroing session. Changes in bullet design, bullet weight, velocity, or loading can change point of impact. Shoppers comparing suitable factory loads can browse ammunition. Bring a target with a visible center and a measurement grid, along with appropriate supports from the accessories category.

Establish and Measure the Initial Group

Place the target at a measured 100 yards. Use a stable support appropriate for the range and follow the support manufacturer’s instructions. If you are unfamiliar with range procedures or rifle zeroing, get qualified instruction rather than attempting to learn by trial and error.

• Keep your finger off the trigger and outside the trigger guard until your sights are on the target and you have decided to shoot.
• Be sure of your target and what is beyond it.

Use the exact same aiming point to produce a deliberate three-shot group. A larger group can offer more information, but three impacts are generally enough for an initial correction when ammunition and range time are limited. Avoid moving the turrets after every impact because a single shot does not reliably identify the group center.

After the group is complete, identify its approximate center. Measure from that center to the desired point of impact, recording horizontal and vertical error separately. For example, write down whether the center is low or high and left or right. If no impacts appear on the target, use a larger target or seek qualified assistance instead of making random turret changes.

Convert the Measurement Into Scope Adjustments

First determine whether the scope uses MOA or mil adjustments and read the click value marked on the turret or listed in the manual. Common click values exist, but they are not universal. The turret label and manufacturer’s instructions control.

MOA Corrections

One MOA spans approximately 1.047 inches at 100 yards and is often treated as roughly one inch for field calculations. Divide the measured error in inches by 1.047 to calculate the required MOA correction. Then divide that result by the MOA value of each click.

As a practical example, a group centered about four inches low at 100 yards requires approximately four MOA of upward correction. If the scope is specifically marked as one-quarter MOA per click, that correction would equal approximately 16 clicks. Verify the turret value before using that example.

Mil Corrections

One mil spans 3.6 inches at 100 yards. Divide the measured error in inches by 3.6 to calculate the correction in mils. Divide that result by the scope’s stated mil value per click. A group 1.8 inches low would require approximately 0.5 mil of upward correction.

Turrets are normally marked with the direction that moves point of impact, but scope designs can differ. Follow the optic manual rather than assuming what an arrow means. Make horizontal and vertical corrections carefully, recording each adjustment so it can be reversed if necessary.

Confirm the Zero and Diagnose Inconsistent Results

After dialing the calculated correction, produce another group using the same aiming point, ammunition, target, and support. Measure the new group center and make a smaller correction if needed. Once the desired relationship between point of aim and group center is reached, produce a separate confirmation group without changing the turrets.

Record the load description, zero distance, turret setting, and any zero-stop setting supported by the scope. Recheck the zero after removing or reinstalling the optic, changing mounting components, changing ammunition, or noticing an unexplained shift in point of impact.

If groups remain too large to identify a useful center, stop adjusting the scope and inspect the setup. Possible causes include loose bases or rings, an unsuitable support, inconsistent ammunition, unclear parallax settings, or a mechanical issue. Manufacturer guidance or qualified assistance can help separate an optic problem from a rifle, mount, or ammunition issue. Supplies for routine upkeep are available under Cleaning and Maintenance.

A 100-yard zero does not mean the bullet will strike at the aiming point at every distance. Trajectory and point of impact vary with the rifle, sight height, cartridge, load, and distance. Confirm any additional distances relevant to your intended use.

Ready to select or update your sighting system? Browse BT Gun Company’s Optics and Sights category for rifle scopes, mounts, and related sighting equipment.