February 1999

Chronographs: Buy Oehler’s 35P For Reliability, Handiness

Oehler’s $225 Model 35 Proof model provided tight data groupings with easy-to-use functions and readouts—better performance than the Alpha Chrony or ProChrono Plus.

Shooters often need to know the actual velocities of the loads they’re using. Whether to know the downrange energy of a particular hunting load, or to plot the trajectory of that new match-grade load, knowing what it is actually doing once it leaves the gun’s barrel is essential. A chronograph should be a simple, painless source for this information.

We selected three models for testing, choosing some that had some evaluative capability, but without printers or computers attached. Most models can be upgraded with software that downloads load performance results to your computer, and can be converted to accept a dedicated printer for instant hard copy readouts. The models we tested were: the Alpha Chrony, $99.95 from Shooting Chrony, Inc.; the Model 35 Proof Chronograph, $225 from Oehler Research; and the ProChrono Plus, $109.95 from Competition Electronics.

How We Tested
All three units were tested with two loads—the Remington Thunderbolt .22 Long Rifle Hi-Speed rimfire cartridge, fired from a Smith and Wesson Model 617 revolver with 6-inch barrel, and UMC’s .357 Magnum 158-grain semi-wadcutters, from a Smith and Wesson Model 686 revolver with 6-inch barrel.

To eliminate as many peripheral factors as possible, all testing was done in one extended session, under relatively constant sunlight, temperature, humidity, and wind. We compared all results within our test, rather than to some external standard of uniform velocity. We assumed, for the purposes of these evaluations, that differences in velocities within a given string were due either to variability in each batch of ammunition or to variability in the chronograph’s ability to measure bullet speeds. Since ammunition should remain relatively constant throughout a given batch, most variances were attributed to the chronographs themselves.

After completing our testing on the range, we examined the data obtained. In addition to average velocities, extreme spread, and standard deviations, we determined relative standard deviation, which we define as the standard deviation (a measure of data spread) compared to the average. This gives some insight into the percentage of spread. Differences here, from one unit to another, were attributed to variability in the chronographs themselves, since the same loads were tested on all three units.

Will these three chronographs give you usable velocity data? We believe so. How comfortably and easily they provide that data is another story. The one other tool essential for good chronography is a good sturdy tripod. It’s possible to get by without one, but you wouldn’t want to try.

Oehler: Model 35 Proof Chronograph
The first thing that struck us was how complicated this unit seems to be. Opening the shipping package reveals an overwhelming array of parts, gizmos, and hardware. But once this initial hump is passed, the remainder of the ride is surprisingly smooth. Unlike the other units, the individual sensors, called “skyscreens” by the manufacturer, are separate. The rail must be placed in the provided tripod adapter, which in turn goes on your tripod. Skyscreens are then placed at either end and the middle of the rail, and the rails and diffusers are then added.

Although this unit takes longer to set up than its competitors, the total time involved is less than 10 minutes. The side rails and diffusers set up more smoothly and easily than either ProChrono’s or the Alpha Chrony’s. All wire connections to the main unit, which automatically turn it on, were a snap. After we aligned the skyscreens with our shooting platform and the targets downrange, we were ready to begin.

Before we even started shooting, the advantage of the Oehler design became apparent. The main unit was set up right there in the shooting bay with us. We needed no accessory units to effectively use the product, nor did we have to keep going back forth from the shooting bay to the unit, as we did with other units. Push-button controls and readout were immediately handy. This is a real advantage over other units we tested.

During actual chronographing, we found the unit perfectly satisfactory, with one exception. If the time between shots was less than about 10 seconds, subsequent shots didn’t register. By itself this isn’t necessarily a problem. But if a lone shooter is evaluating a new load and puts his shot string—say, ten rounds—into the target without looking at the readout, he might not be aware that the unit is missing one or more readings.

Scrolling through the stored and calculated information after each shot string was effortless. We did run into a minor glitch while trying to use the “Edit” mode, which allows the user to remove specific shot velocities from a given data string and re-calculate the statistics. This data then reappears after the “summary” information is reviewed.

But we couldn’t get to that function. When we kept pressed the “Edit” button, the unit to reset, so we had to repeat shot strings. Further study of the manual revealed that the Edit function is controlled by an internal switch, like those old daisy-wheel and dot-matrix printers’ DIP switches from about a decade ago. Other switches control printer use, and variable distances between the first and last skyscreens. So we turned the unit off, changed the appropriate switch, and were immediately back in business.

If stored data is critical, be sure you’re in Edit mode before you try using it. Otherwise, trying to use this mode will delete your data. The unit we tested came with the Edit mode off. The 30-page instruction manual, although a bit intimidating at first blush, is well-written and well-organized. It describes in detail how the unit is assembled, set up, and operated. Our unit came with the manual for the Model 35P, which has a built-in printer.

The Oehler unit also showed the smallest average of relative standard deviations. This may well be due to the system’s three sensors rather than the two the others use. This allows the Oehler to calculate two velocities—the test velocity itself and a “proof” one. These are compared electronically to determine if a significant difference exists, which is then flagged.

Competition Electronics: ProChrono Plus
This chronograph comes as one unit, with separate guide rods, black side shields and diffusion hoods. This design made it very easy to mount on our tripod in just a couple of minutes.

The next task was to set up the diffusion system. For most chronographs, light diffusion is unnecessary on a cloudy or overcast day, although the side, guard or guide rails should be used to guide shot placement. This part is a little tricky; the design for attaching the side rails to the top hoods is clumsy, in our view. However, their flexibility makes it possible to store the hoods and rails while still attached. They will fold up for easy storage. Subsequent sessions can skip this hood-to-rail assembly.

When we began our .22 rimfire shooting, we were surprised to see that no velocities were registering. Planning tests with both .22 rimfire and .357 magnum centerfire ammo, we had placed the chronograph about 10 feet in front of the front barrel support we used. This is per manufacturer’s directions, which recommended 5 to 10 feet for handguns.

“Distance is not critical,” read the directions, “but must be far enough away to keep from blowing apart the diffuser hoods with the muzzle blast.”

Trial and error showed that moving the unit closer—to about five feet in front of our firearm’s muzzle—allowed it to register properly. This worked fine until we began our testing with .357 magnum ammo, when the muzzle blast did disrupt the diffuser hood assembly, as promised. So, back the unit went to its original 10-foot position.

Operation of this unit takes some getting used to. To get through each function on the machine, the same button must be pressed at least 13 times—more if there is more than one velocity reading stored, as there undoubtedly will be. The directions, a single page long, are much less clear than we’d like. The section “Push Button Control” is one very long paragraph, describing over a dozen functions. Good luck finding the specific information you need.

We also had a problem reviewing data. Imagine you’ve got several loads you want to examine. You’ve made the shots, and now you need to review and record your results. Unless you’ve paid an extra $25 for an accessory remote control unit, you have to keep going to the machine and stand there pressing the control button—an inconvenient characteristic, we thought. This is especially bothersome if you’re at a crowded range and you need to wait until the firing line is clear.

Finally, relative standard deviations for this unit were a bit higher than those recorded on the Oehler, but not high enough to make us question the unit’s accuracy.

Shooting Chrony: Alpha Chrony
Arriving in the most compact packaging of the three, this little unit is similar to the ProChrono in that it is one unit with separate diffuser components. The main unit actually unfolds for use, and the diffuser components, some of which are reminiscent of a Chinese puzzle, are then assembled.

Operation was simple. Shot velocities were recorded without difficulty, and all functions went off painlessly. Like the ProChrono, all operation must be done on the machine itself unless the optional remote control is in place. Shooting Chrony’s remote, costs less than $13—about half the cost of ProChrono’s remote. For $20 more, the Master Alpha features a remote unit that includes an LED data readout, a good feature for those whose eyesight isn’t what it used to be, or who hate to squint. The instruction manual is not as good as Oehler’s, but certainly provides all the information needed. One drawback: the manual is designed for four separate models and their variants, so it’s necessary to assure that what you’re reading actually applies to your model.

Relative standard deviations were the highest of the group, but not distressingly so. We were still satisfied with its accuracy.

Gun Tests Recommends
Our choice is the Oehler Model 35 Proof Chronograph. At over $200, this unit is the most expensive of the group we tested, but we liked the tight data groupings it provided, especially for the higher-velocity load. We believe that the third skyscreen and its data-checking function is worthwhile. This chronograph’s ease of use—by having all functions and readouts right at your fingertips—appealed to us as well. We recommend it.

The Shooting Chrony Alpha Chrony is a solid buy, if the Oehler is more than your budget can manage. At just under $100, this one is highly affordable. Be sure to include at least the push-button remote for $13 dollars more. We’d spend another $7 and get the Master remote that includes LED readout. Simplicity of use, set-up, and position earned praise for this unit.

The Competition Electronics ProChrono Plus provided performance comparable to the Chrony unit, and its relative standard deviations were actually a tad better. But we felt that its higher cost ($110, plus $25 for a remote control), combined with more difficulty of use and access to features, made it less of a value.