Check that the scope rings and rail bolts are tight, and that you are shooting the bolt weight your bow's manual specifies. A loose mount or the wrong bolt weight makes every adjustment below meaningless.
A package crossbow arrives roughly aligned, not zeroed. Zeroing is a short, boring, repeatable process, and doing it in the right order is the difference between twenty bolts and an entire afternoon.
Step 1. Set up close
Start at twenty yards, on a solid rest, with a large backstop. Close range keeps early bolts on the target so you can see what the bow is doing, and a big backstop saves you from losing bolts while it is still wrong.
Step 2. Shoot a group, not a shot
Fire three bolts before touching a turret. One bolt tells you nothing - it can be your flinch, a bad rest, or a marked bolt. The centre of a three-bolt group is the only thing worth adjusting to.
Step 3. Move the group to the mark
Adjust so the group moves toward the aiming point. Scope turrets are marked for the direction the point of impact moves, and clicks are usually a fraction of an inch at 100 yards - which at twenty yards means it takes far more clicks than feels reasonable. Count them, move deliberately, then shoot another group rather than guessing.
Step 4. Confirm, then step back
Once a group sits on the twenty-yard mark, move to the distance your scope's top reticle is designed for, usually thirty or forty yards, and confirm there. Use the reticle marks as designed rather than re-zeroing at each distance - multi-reticle crossbow scopes assume the top mark is your zero.
Step 5. Verify the lower marks
Shoot the lower reticles at their intended distances and write down where they actually hit. They are calibrated for a speed and bolt weight that may not match yours exactly, and a bow that is perfect at twenty can be several inches off at fifty. Those written numbers are your real drop chart.
| What you see | Most likely cause |
|---|---|
| Group is tight but off-centre | Normal - this is what turret adjustment is for |
| Group is wide and scattered | Rest, hold, or mixed bolt weights before it is the scope |
| Point of impact wanders between sessions | Loose rings or rail bolts |
| One bolt always flies off | Check that bolt for a damaged nock or vane |
| Good at 20, badly off at 40 | Reticle calibration does not match your speed - record real numbers |
Mistakes that cost people an afternoon
Adjusting after every single shot. Shooting from a different rest than you will hunt from. Mixing bolt weights mid-session. Starting at forty yards, missing the backstop, and spending the rest of the day looking for bolts in grass.
Keep everything else constant
Zeroing only works if the bolt is the same every time. Use identical bolts of the same length, weight and nock type, with field points that match the weight of the broadheads you intend to hunt with. Mixing a light practice bolt with a heavier hunting bolt changes the point of impact and quietly undoes the whole session.
Mark your bolts and set aside any that have taken a hard hit. A bolt with a hairline crack or a damaged vane will fly wide and send you chasing a scope problem that does not exist.
Multi-reticle and rangefinding scopes behave differently
A standard multi-reticle crossbow scope assumes a fixed speed, and the lower marks are calculated from it. If your bow shoots slower or faster than that assumption - and most do, at least slightly - the lower marks will be progressively off. That is normal and it is not a fault; it is why step five of the process exists.
Rangefinding and illuminated scopes calculate or adjust for the measured distance, which removes most of that discrepancy. They also introduce batteries and electronics to a device that is otherwise mechanical, which is a trade worth making deliberately rather than by accident.
Broadheads change the answer
Field points and broadheads do not always land in the same place. Fixed-blade broadheads in particular catch air and can steer a bolt, so a bow that is dead-on with field points can be several inches out with hunting heads. Before the season, shoot at least a few of your actual hunting bolts with the actual broadheads and confirm - or adjust for - the difference. Mechanical heads usually track closer to field points, which is a large part of why people choose them.
Keeping the zero
Zero drifts. It drifts from transport, from a knock in a truck bed, from screws working loose over a season, and from a string that has stretched or been replaced. Check it at the start of every season and after any hard impact, and re-check after a restring - a new string is effectively a new bow as far as your scope is concerned.
| Check | Frequency |
|---|---|
| Scope rings and rail bolts tight | Every session |
| Bolts undamaged, matched weight | Every session |
| Rail lubricated per manual | Per manufacturer's interval |
| Confirm zero at 20 and at your top reticle distance | Start of season, after any impact |
| Confirm broadhead point of impact | Before hunting, every season |
| Re-zero completely | After any string or cable replacement |
Scope quality is part of why zeroing goes smoothly or badly - a scope that will not hold its setting cannot be fixed by procedure. It is one of the things we score under what you get in the ranking.