From the vault: A few tips on how to use a chronograph from Hugh Birnbaum. As published in the July 1992 issue of Shooting Sports USA.
Chronographs and Competitors By Hugh Birnbaum
Chronographs are among the most misunderstood accessories shooters use. This is because they have an aura of high-tech wizardry that beguiles the first-time user with hopes of decrypting a ballistic Rosetta stone. The fact is, a chronograph can tell you one thing and one thing only: how fast a bullet or other rapidly moving object travels between the chronograph's start and stop sensors. That is the basic truth the chronograph reveals. All else is embroidery or interpretation.
Like many competitive shooters, I had never used or owned a chronograph because I never felt a pressing need to know how fast a shot charge or bullet or pellet was speeding down range. As long as whatever I shot arrived at the desired area or point-of-impact I was content. I was not concerned with knowing precise velocities. When firing factory ammunition I relied on the manufacturer's ballistic tables and when reloading I accepted at face value the velocities published in the data manuals.
And then one day I had an idea for an article that would involve considerable reloading and test firing. The editor with whom I discussed it was enthusiastic but it was obvious from our conversation that he expected chronograph data as part of the package, so I promptly acquired a chronograph. It was a simple, self-contained unit. It had no printer and performed no calculations, but it was small, lightweight and serviceable. I still have it as a back-up to its successor, an Oehler 35P Proof Chronograph. The Oehler is much more elaborate and there are more components to assemble when setting up at the range. However, the more involved setup is more than offset by the convenience of a built-in printer and ability to provide all the number-crunching I needed at the push of a button. Ultimately, though, both chronographs tell me the speed of a passing projectile. From the perspective of a competitive shooter you may well ask, "So what?"
Some action-shooting games require ammunition that meets or exceeds specific minimum power criteria, and competitors' cartridges are sampled for on-site chronographing to ensure that the relationship between velocity and bullet weight is appropriate. If your ammunition is a tad slow, you may be compelled to compete in a disadvantageous category with built-in scoring penalties. If it is much too slow, you may be barred from competing. Checking ammunition you purchase or reload to make sure it delivers the speed you expect and need will avoid such disappointments.
Smallbore rifle and Smallbore Hunter's Pistol silhouette shooters can benefit from using a chronograph when test firing various brands and types of cartridges. Occasionally, two or more brands or types or production lots of rimfire ammunition yield equally good accuracy in a particular rifle or pistol. If price and availability are also about the same, chronograph results could well tip the balance. All other factors being equal, my own inclination would be to pick the ammunition that showed a clear advantage in velocity, which would help avoid the sinking feeling of hearing the bullet strike steel, but not seeing the target fall. if velocities are too close to differentiate, select on the basis of maximum consistency of velocity from shot to shot.
Competitive shooters who handload may find a chronograph nearly indispensable.Competitive shooters who handload may find a chronograph nearly indispensable. One fact of life in handloading is that the published velocity for a given combination of components may or may not correspond closely to the velocity you are actually achieving. Small variations in production lots of primers, powders, bullets, cases, assembly techniques and firearms can account for a significant difference between the velocity a technician achieves in laboratory load development and the velocity you or I obtain. Sometimes knowing there is a difference matters to me and sometimes it doesn't.
When I prepare handloads for offhand practice with a .45 ACP auto pistol, for example, minor velocity discrepancies don't bother me because I can easily correct the sight settings at 50 feet, 25 yards and 50 yards. I shoot regularly at ranges with target supports at all three distances. When I work up a load for Hunter's Pistol silhouette, though, I have a bit of a problem. The outdoor range where I shoot centerfire pistols has target supports at 50 and 100 yards, but not at 40, 50, 75 and 100 meters. Range regulations and topography prevent erecting improvised target supports at the proper silhouette distances. My solution to the problem was to chronograph a load I had previously tested for accuracy. Once I knew the actual velocity, I consulted the bullet manufacturer's comprehensive trajectory tables, which showed me that zeroing the scope on the T/C Contender for a center of impact about an inch high at 100 yards would allow me to hold the crosshairs at the junction of the leg and body for chickens, just under the belly for pigs, about an inch above the leg-body junction with turkeys and dead center for rams. During the match the following week, I never had to touch the elevation knob on the scope. The bullet splashes on the white silhouettes indicated that the combination of data from the chronograph and the trajectory table had given me a "universal" setting for the load that would let me hit as well as I could hold. When I missed, it was me, not the scope setting.
Another important application of the chronograph for handloaders lies in quality control. Every time I have to change to a new batch of primers, powder, cases or bullets, I make a point of assembling and chronographing at least 10 rounds of a load I have chronographed previously. By comparing the latest results with the prior results, I can see quickly whether or not the new lot of whatever component was changed will make a significant difference in velocity. If it does, I can live with it if it is within safe bounds and doesn't degrade accuracy, gun function or usefulness. Otherwise, I have the option of adjusting the powder charge to bring the velocity back to the previously obtained level. Clearly, chronograph data have important applications in keeping handloads safe as well as accurate and consistent.
These examples are merely tantalizing glimpses of the possibilities chronographs can offer shooters with a taste for precision. As stated earlier, I shot for a long time before learning to use a chronograph and I didn't feel I was missing anything. Now, I consider it as important as any of my competition guns and I would find it difficult to live without one. Coming from someone who tends to be suspicious of most electronic gadgets, that is high praise, indeed.