How to Zero an ACOG Scope at 100 Yards? A Step-by-Step Approach

Zeroing, or sighting in, your ACOG (Advanced Combat Optical Gunsight) scope is an important process to ensure accuracy on the range. While scopes come pre-aligned from the factory, taking the time to zero it yourself to your specific rifle is crucial for precision shooting.

When zeroing a scope, the goal is to adjust the windage and elevation so the point of aim matches the point of impact at a set distance, usually 100 yards or meters. This ensures the reticle crosshairs align with the bullet trajectory from your particular gun.

Zeroing in an ACOG provides maximum accuracy and consistency for your preferred range and caliber. Here are the step-by-step instructions to properly zero an ACOG scope at 100 yards.

Step 1 – Choose an Appropriate Range

First, select a range or shooting area with targets positioned at 100 yards distance. Ensure there is a solid bench rest or stable shooting platform available. The range should accommodate firing at paper targets downrange for clear visibility of bullet impact.

Safety is paramount, so ensure a safe downrange area and proper supervision of the range. Communicate to all present that you will be zeroing a rifle scope. Follow all range commands and ceasefire procedures.

Step 2 – Mount the Scope Properly 

Mount the ACOG scope securely to the rifle’s Picatinny or weaver rail system based on manufacturer specifications using quality rings and bases matched to the rifle and scope. Improper mounting can prevent holding zero.

Torque the scope ring screws down incrementally in an X pattern to the recommended inch-pound rating. Do not over-tighten. The recoil lugs should fit snugly in the mount. Confirm the scope has minimal play when installed.

Step 3 – Establish a Stable Shooting Position 

Use a bench rest, bipod, or stable prone position to create a solid rifle support. The goal is to eliminate as much human error from the shooting process as possible. Sandbags can help stabilize the front of the rifle.

Align the reticle to target at 100 yards. Control breathing patterns and relax muscles not needed for shooting to minimize rifle movement. Maintain consistency in form and aim for all test shots.

Step 4 – Fire a 3-5 Shot Grouping 

Load 3-5 rounds into the magazine. Fire shots in succession at the 100-yard zeroing target, focusing on proper trigger pull and minimal disruption of aim between shots.

Using a spotting scope or binoculars, identify the bullet hole grouping on the target. Draw a circle around the tightest 3-shot cluster if all shots did not hit the same point of impact.

Step 5 – Adjust Windage and Elevation 

If bullet impact is centered, no scope adjustments are needed. But if the grouping is off-center, use the windage and elevation turrets to bring the point of impact to match the point of aim.

For windage errors, turn the horizontal dial to move the impact left or right. For elevation errors, use the vertical adjustment dial to move the impact up or down. Refer to scope instructions for MOA adjustment values.

Step 6 – Re-Test Adjustments with Additional Shot Group 

After adjusting the windage and elevation, fire another 3-5 shot group at the same 100-yard target. Spot and assess the new grouping. Make minor additional tweaks to bring the point of impact precisely to the point of aim.

Repeat this process until satisfied with the 100-yard zero. Record the number of MOA turned on both knobs to track your adjustments.

Step 7 – Confirm Zero at 100 Yards 

When confident that adjustment dials are zeroed at 100 yards, fire a 5-shot group to confirm. All shots should strike within 1-2 inches of each other centered on the bullseye at 100 yards when the aim is consistent.

Make any final minor adjustments needed to fine-tune the zero. Record the final adjustment values for the rifle scope combination. The scope is now precisely zeroed for 100-yard shooting.

Step 8 – Consider Zero Stop Adjustments

Some ACOG scopes feature Zero Stop turrets that allow setting a mechanical zero point for the adjustment range. Once zero is established, you can set the zero stop to prevent accidentally dialing below 100-yard zero when adjusting for other ranges.

This provides a quick reference point and protects your established 100-yard zero if dialing in adjustments for 300, 400, or 500-yard shooting distances. Refer to manufacturer instructions for setting Zero Stop adjustment limits.

Step 9 – Label Your Zero 

As a final step, mark the 100-yard zero on the adjustment dials or turret caps to save the dialed-in reference point specific to your rifle and scope. This avoids losing zero if inadvertently turning knobs later on.

You can now accurately engage targets at 100 yards relying on your ACOG bullet drop compensated reticle. Getting in frequent practice at your zeroed distance leads to consistent shooting and reinforces proper form. Zero your scope regularly to account for any shifts over time.

Bonus Tips

Here are some additional tips for zeroing an ACOG sight at 100 yards:

• Use a good quality target. A bright orange or yellow target is ideal.
• Make sure that your rifle is properly secured in the bench rest.
• Use a consistent firing grip.
• Aim carefully at the center of the target.
• Fire slowly and carefully.
• Be patient. It may take several groups of shots to zero your ACOG sight.

Once your ACOG sight is zeroed at 100 yards, you can use the built-in bullet drop compensator (BDC) to aim at targets at longer distances. The BDC is a series of dots or hash marks on the reticle that correspond to different distances. For example, the 300-meter BDC dot is designed to help you aim at a target at 300 meters.

To use the BDC, simply aim the tip of the chevron reticle at the target and the bullet will drop to the point of impact at the corresponding distance. For example, if you are aiming at a target at 300 meters, you would aim the tip of the chevron reticle at the target and the bullet would drop to the 300-meter BDC dot.

Conclusion

Zeroing an ACOG scope requires careful mounting, shooting technique, and dialing in windage and elevation adjustments. Sighting in at 100 yards provides a reliable zero foundation for field use at that distance and for dialing in variable ranges. Follow these target shooting steps to get the utmost accuracy from your ACOG scope. Consistently zeroing your optic maximizes precision for hunting, tactical, or competitive shooting.