What Is Zeroing (Sighting In)?

Zeroing (Sighting In): definition

Also called: sighting in, sight-in, zero, zero distance, boresighting

Zeroing means adjusting the scope’s windage and elevation until the bolt’s point of impact matches the aim point at a chosen distance. That distance is the zero distance. Every other mark on a BDC reticle, and every holdover you apply, is measured from the zero.

The process is the same in outline for every scope: fire a group from a stable rest, measure where the group sits relative to the aim point, convert the offset to clicks using the scope’s MOA value, adjust the turrets, and confirm with a second group. The detailed steps are in our guide on how to sight in a crossbow scope.

A zero is only valid for the setup it was made with. Changing the bolt weight, tip weight, string, nock or scope mounting shifts the point of impact, so the zero should be re-checked after any change. Many reticles state a zero distance, such as the 40-yard zero on the Vortex Crossfire II.

Clicks from a measured offset

Common zero distances and what they suit

Why Zeroing matters

A scope that is not zeroed can look precise on the target while being consistently wrong. Zeroing converts group tightness into accuracy.

The zero is also the reference for hold marks. If your crossbow is zeroed at a different distance than the reticle assumes, every mark is shifted.

Zeroing is where bad habits show up. Inconsistent rest, grip or cheek weld spreads the group and makes the adjustment unreliable.

How to read it on a spec sheet

• Spec sheets sometimes state “zero at 40 yards” or similar. That is the distance the printed marks assume.
• Reticle instructions list the speed range for which the zero and marks are valid.
• If a scope says “auto-calibrated”, it still needs a verification group at one distance.
• Click value, such as 1/4 or 1/2 MOA, tells you how finely you can set the zero.
• Turret caps hide the adjusters on many scopes; remove them as the manual directs.

Common mistakes

• Zeroing from an unstable rest. Group centre moves with every wobble.
• Chasing single bolts instead of a group. Adjust from the centre of a five-bolt group.
• Zeroing with field points, then hunting with broadheads, without checking that they land together.
• Moving turrets the wrong way. Read the direction arrows and confirm on target.
• Forgetting to lock or replace turret caps after the final adjustment.

A short zeroing routine

1. Choose a safe range with a proper backstop and follow your crossbow’s safety rules from the manual.
2. Shoot a first group of three to five bolts from a stable rest at 20 yards.
3. Measure the offset from the aim point and convert it to clicks with the formula above.
4. Adjust windage first, then elevation, and shoot another group.
5. Move to your zero distance, confirm, then check other distances. Details: how to sight in a crossbow scope.

In my testing

Every review starts by zeroing the scope before I shoot strings over the chronograph and five-bolt groups at fixed distances, measured centre to centre. In the scope reviews I also noted whether the zero held; the TruGlo 4x32 and the EVO-X Marksman Elite showed no zero shift across their durability and recoil testing. How I test.

See it in our reviews

• Vortex Crossfire II 2-7x32 — rated 4.6/5
• TruGlo 4x32 Compact Scope — rated 4.3/5