Three Uses for a Chronograph

There’s no doubt we are living in the golden age of long-range shooting. And the reason this is the case is largely because of the technology available. While rifles and ammunition are better than they’ve ever been, much of our long-range capability comes from the availability of laser range-finding devices to measure distance and chronographs to measure bullet velocity.

I first dove into the world of chronographs many years ago and have continued upgrading as the technology has evolved. Today’s compact Doppler radar-based units are incredibly capable, and I can’t imagine a serious shooter being without one. Most shooters understand that a chronograph measures bullet velocity, but what’s often overlooked is how valuable the data can be beyond that single number. Here are three ways to use chronograph data that, taken together, make a compelling case for every precision shooter to own one.

Accurate Trajectory Prediction

The most obvious use of the velocity information a chronograph provides is to calculate a bullet’s trajectory. By now, I think we all know that relying on manufacturers' published velocity data is not accurate enough for precision rifle work. Factors such as temperature, barrel length, lot number changes, and more all contribute to making published data just an estimate. Whether it’s for factory ammo or the estimate in a reloading manual, these published numbers are good guidelines, but far more precise information is needed to hit a target at distance.

Accurate velocity numbers, combined with a good ballistic program that factors in environmental conditions, will provide bullet drop at distance, wind drift numbers, time of flight, and even supersonic/transonic behavior. All these are needed to accurately predict a bullet’s trajectory, and a chronograph provides the raw numbers to do it. That alone is enough reason to own and use a chronograph, but they can do more.

Monitor Consistency

A less-used application for a chronograph is its ability to monitor consistency. While all chronographs provide an average velocity for a series of shots, the modern ones will also spit out consistency numbers. These are expressed in either extreme spread (the difference between the fastest and slowest shots) or standard deviation (a statistical measure of how consistent bullet velocity is). Because it’s a predictive number, standard deviation is the most valuable of the two. However, it’s fair to ask why consistency is important.

First, it’s necessary to understand that a series of shots will never have the same velocity, and that changes in velocity will affect the downrange trajectory of a bullet. Add those two facts together, and we can understand the value of consistency. Poor velocity consistency is observed downrange, resulting in high vertical dispersion. It’s unrealistic to hope for every shot to be the same velocity, so the best we can hope for is consistency to be high, with little shot-to-shot variation. Long-range shooters typically aren’t happy unless standard deviation values appear as single digits, indicating excellent consistency.

Safety for Handloaders

And perhaps least understood is a chronograph’s ability to provide safety information, particularly for handloaders. Those estimated velocities in reloading manuals mentioned earlier, while just estimates, are still valuable information. If a load produces velocities significantly higher than indicated in the manual or higher than those of previous loads using the same recipe, consider it a warning sign. There is no free lunch; unusually high velocities mean unusually high pressures. The cause could be a change in propellant lot number, an increase in ambient temperature, a carbon ring, or a host of other issues. A chronograph won’t tell you where the problem is, but it will alert the observant shooter that a problem needs to be addressed.

Chronograph readings can also alert shooters when velocities drop below expected levels. While this is rarely a safety concern, it can become a significant performance issue, especially when a handload that normally delivers consistent speeds starts showing unexplained velocity loss. That's why careful observation and record-keeping are so important. To get the most from any modern chronograph, shooters must look beyond the raw numbers and focus on trends over time. These remarkable instruments provide a wealth of valuable information, but only if we take the time to interpret the data correctly and use it to its full potential.

ABOUT THE AUTHOR

Al Voth calls himself a "student of the gun." Retired from a 35-year career in law enforcement, including nine years on an Emergency Response Team, he now works as an editor, freelance writer, and photographer, in addition to keeping active as a consultant in the field he most recently left behind—forensic firearm examination. He is a court-qualified expert in that forensic discipline, having worked in that capacity in three countries. These days, when he's not working, you'll likely find him hunting varmints and predators (the 4-legged variety)