Crossbow Chronograph: What It Measures

Crossbow Chronograph in plain terms

Crossbow Chronograph meaning: A chronograph measures the real speed of a bolt in feet per second as it passes the sensor, so you can check a crossbow against its rated FPS.

Also called: chrono, bolt speed meter, arrow chronograph, measured speed, chronographed speed

A chronograph is a device that measures how fast a projectile is travelling. For crossbows it reports bolt speed in FPS, measured a short distance in front of the crossbow rather than calculated from a spec sheet.

Its value is that it turns a manufacturer's claim into a checked number. A rating is taken with one bolt weight under the maker's conditions; a chronograph shows what your crossbow does with the bolt you actually shoot.

Speed varies a little from shot to shot, so a single reading means little. Shooting several strings and reporting the lowest and highest reading gives a range that shows both the speed and how consistent the crossbow is.

Rated versus chronographed speed in reviews

Each row comes from the review file, measured in five shot strings with a 400-grain bolt unless noted.

Why it matters

Box speeds drive many buying decisions, and they are not always comparable. A chronograph reading with a stated bolt weight lets you compare crossbows fairly, which is how the fastest crossbows ranking on this site is ordered.

Your real speed also sets your scope. A reticle or speed ring is calibrated to a speed band, so a measured figure is the number to enter in the scope speed matcher and the kinetic energy calculator.

A drop in measured speed over time can be an early sign of a worn string or another problem, so a reading at the start of each season is a useful baseline.

How to read it on a spec sheet

• Check the bolt weight. A reading with a 400-grain bolt is not comparable with one taken with a 350-grain arrow.
• Prefer a range from several shot strings over a single "best" number.
• Compare the range with the rating: a few FPS either side is normal; a large shortfall is worth investigating.
• Note whether a figure is your reviewer's own reading or a published test from elsewhere. Reviews on this site label them separately.
• Remember that speed is measured near the crossbow; the bolt slows downrange.

Common mistakes

• Comparing one crossbow's chronograph reading with another's box rating.
• Judging a crossbow on a single shot.
• Shooting a bolt lighter than the manual's minimum weight to chase a higher reading, which can damage the crossbow.
• Setting up the chronograph without a safe backstop or without following its instructions.
• Assuming energy is measured. Kinetic energy is calculated from the measured speed and the bolt weight.

How to chronograph your crossbow safely

1. Read the chronograph instructions and your crossbow manual first.
2. Set up at a safe range with a proper backstop and nothing downrange.
3. Place the chronograph at the distance its instructions specify, with the bolt path clear of the unit.
4. Use the bolt weight you hunt with, and note it.
5. Shoot several strings and record each reading, then compare the range with the rating.

In my testing

Every crossbow review on this site that reports a measured speed comes from five shot strings over a chronograph, almost always with a 400-grain bolt, reported as a low-to-high range. The TenPoint TRX Ultra read 511 to 517 FPS against its 515 FPS rating, and every crossbow in that ranking landed within a few FPS of its rating. How I test.

See it in our reviews

• TenPoint TRX Ultra — rated 4.9/5
• Ravin R470 — rated 4.7/5
• Killer Instinct Logix 435 — rated 4.2/5