What Is Trajectory (Bolt Drop)?

Trajectory (Bolt Drop): definition

Also called: bolt drop, arrow drop, bolt trajectory, arrow trajectory, drop

Trajectory is the path a bolt takes from the rail to the target. From the moment it leaves the string, gravity pulls it downward, so the path is a curve rather than a straight line. Bolt drop is the amount the bolt has fallen below the line of the bore at a given distance.

Time in the air is what drives drop. A slower bolt takes longer to cover the same distance, so gravity has longer to act on it. That is why a heavier bolt shot from the same crossbow, which leaves at a lower FPS, lands lower at 40 yards than a lighter one. The bolt also loses speed to air drag as it travels, so drop grows faster at longer ranges than a simple speed figure suggests.

Because the scope sits above the rail, the line of sight and the bolt path cross. When you zero at 20 yards, you are choosing the distance where the curve meets your aiming point. A multi-dot or BDC reticle adds aiming points below that for longer distances, and each is calibrated for a speed range, because a different bolt speed produces a different curve.

Drop in a vacuum (no-drag simplification)

Why Trajectory matters

Drop is why distance judgment matters. A bolt that hits the aiming point at 20 yards will land well below it at 40 yards, and misjudging the range by a few yards at longer distances moves the impact more than the same error close in. Knowing your bolt's curve is part of shooting ethically and safely, with a backstop that covers misses.

It also explains why changing bolts or tips means re-checking your zero. A heavier bolt, a heavier tip or a different crossbow changes speed, and a change in speed changes where every aiming point lands. The bolt drop chart lets you compare the effect of different speeds before you head to the range, but your own shooting at known distances is the final check.

How to read it on a spec sheet

• Manufacturers rarely list drop directly. Start from the listed FPS and remember it is usually measured with a lighter bolt than many people shoot.
• If a scope lists a speed range for its reticle, check that your actual bolt speed falls inside it.
• Read published drop charts as a guide for a specific speed and bolt weight, not as a promise for your setup.
• Compare drop figures only at the same zero distance. A chart zeroed at 20 yards and one zeroed at 30 yards are not comparable.
• Remember that downrange speed is lower than launch speed, so long-range figures depend on how much speed the bolt keeps.

Common mistakes

• Assuming a reticle marked for 20, 30 and 40 yards is correct without shooting each distance with your bolts.
• Changing to heavier bolts or tips and not re-checking the aiming points.
• Using the vacuum formula as an exact answer. It ignores drag and underestimates real drop.
• Guessing range at longer distances, where a small distance error produces a large vertical miss.
• Comparing drop charts that use different zero distances or bolt weights.

Check your real drop

1. Zero your scope at the distance the manual recommends, usually 20 yards, with the bolts and tips you will actually shoot.
2. Measure out 30, 40 and further distances with a tape or rangefinder rather than pacing.
3. Shoot a small group at each distance using the matching aiming point.
4. Note how far each group lands from the aiming point and adjust the scope speed setting if it has one.
5. Write the results down and repeat after any change of bolt, tip or crossbow.