Do you REALLY need a chronograph?
by B.B. Pelletier
Many airgunners have chronographs and more get them every day. But why are they buying them? Do you really need a chronograph to enjoy airgunning?
A chronograph is like a fish scale
They call fish scales "de-liars." You can guess why. Chronographs are in the same category of equipment. They tell you something about your airguns without changing how they shoot. A chronograph measures the velocity of a pellet, bullet or arrow in feet per second or meters per second. With that information, you can use the formulas here at Pyramyd Air to determine how powerful your airguns are.
Some chronographs are very affordable
For over a decade, chronographs have been affordable, with the least expensive costing under $50. The Shooting Chrony brand out of Canada starts at about $65, and they average just under $100. The units are small, lightweight, rugged and run on batteries, so you can take them anywhere. They need a good, even light source to work correctly. Although their screens are very close together and their clock speed is low by today's standards, the Shooting Chrony is accurate enough for the hobby shooter.
Shooting Chrony makes a range of rugged,
inexpensive chronographs that airgunners love.
Next up in price is the Pro Chrono brand. They sell for around $100 and have a few more features than the Shooting Chronys, but most of those are for computer input. Like the Shooting Chrony, they can drive an optional printer, which is a nice thing to have if you plan on doing a lot of experimentation. Their clock speed is also relatively slow, but they still give reasonably accurate data when used correctly.
The Pro Chrono brand is just a trifle more expensive and has the same nice features of the Shooting Chrony, plus it connects to some computers.
How chronographs work
A chronograph contains a crystal "clock" that ocillates at a precise, known frequency. When the shadow of a pellet (that's why lighting is so important) passes over a start screen, the clock starts running and an accumulator stores the impulses. When the shadow passes over the stop screen, the clock stops and the number of impulses is tallied in a computer. Since the crystal oscillates at a regular rate, the computer can turn the number of pulses into elapsed time, which equals the speed the pellet was moving.
If you don't use them right, you can fake out some chronographs
If you don't shoot STRAIGHT through the less expensive chronographs, you can get readings way above and below the actual velocity. By shooting on a slant, the chrono will read slower than it should, because the slanting path of the pellet is longer than it would be if shot straight. An expensive chronograph senses this and warns you that the shot seems incorrect, but the lower-priced ones don't.
Top of the line
The Oehler (pronounced Ehler) 35P printing chronograph is the best available. Whenever you read an article in a mainstream gun magazine where velocities are quoted, it's always an Oehler. The chronograph has a second "proof" channel to check the primary reading, and the crystal clock is 40 times faster than the less expensive ones. All the powder manufacturers plus the government use Oehler chronographs exclusively.
The Oehler 35P chronograph is the recognized world standard instrument.
Having said all that, I still contend that you don't need a chronograph to enjoy an airgun. It's a nifty thing to have, as long as you don't end up more fascinated by the numbers than by where the pellet strikes. Because THAT, after all, is the primary objective.