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.

11 Responses to “Do you REALLY need a chronograph?”

  • Anonymous Says:

    Do you have any opinion on the British-style Combro chronograph?

    http://www.combro.co.uk/cb625.html

    Thanks!

  • B.B. Pelletier Says:

    Yes, I do. I owned a Combro and found it very limited. First, it doesn’t fit the muzzle of all guns, so you are limited as to when you can use it. Second, the screen spacing is less than two inches, so accuracy is dubious. You get a number, but who is to say what it means? Third, because it uses IR screens, it doesn’t work well in brightly lit situations. I don’t consider a Combro to be a serious chronograph.

    B.B.

  • Anonymous Says:

    I have seen a number of people use a microphone and the freeware Audacity sound editor to make speed measurements. for someone on a budget (or has a long toy list) this can give rough speed info for little money.
    I dont use a chrony all that much, so it is hard to justify the expense for such and item. That leapers AO scope however…

  • B.B. Pelletier Says:

    Wow! Can you please tell us more about this homemade “chronograph?”

    B.B.

  • Yarzak Says:

    I have not tried this but pretty much follow the concept. BB am interested in what your thoughts are.

    Ray

    The following it is copied from:

    http://www.reviewcentre.com/review_comments156260.html

    Comment by hotsky on 10th May 2005 | other work
    Hi; How did you make the Chrony? I always wanted one, but don’t have the extra money :(

    Comment by psy303 on 10th May 2005 | other work
    hi hotsky, extra money ??? i want a chrono too !!! now my self made chrono: i do the same thing that a chrono do. i measured the time, that the pellet net for a known distance. i measured at 5 meters. so all my results aren´t the muzzle velocity. my results are the average pellet speed for 5 meters. so the muzzle velocity is a few percent higer. but for me it is accurate enough. to build your self made chrono you need: a pc with sound card, a mike, and a recording program ( i used audacity, because it was the first i found for free. this prog isn´t very good but it works).
    1. place mike exacly at the half distace to the target and start the recording.
    2. shoot an exactly known distance from the muzzle to the target. ( i shoot at 5 meters )
    3. stop recording and do some math.
    with the audacity prog ( or any other ) you can see the recording as a wave form as a funktion of time. you can exactly see when you have fired and an when the pellet hit the trap. the difference is the time that the pellet neet for this distance. with this information you can calculate the average pellet speed for this distance. i do this measuring method with 3 different 7.5 joule weihrauch guns, and i measured with the first gun 173m/s, the second 176m/s, the third 179m/s. this shows how accurate this method is. example for my gamo p800: i used RWS hobby pelets with 0.45 gramms at five meters. i can see that i shot 14.12494s after the recording start. the pellet hit the trap after 14.17805s. so the difference is 53.11ms. this is the time that the pellet need for five meters. the SI unit is for speed is [1m/1s]. so i devide the difference by the distance. the result is 53.11ms/5m = 10.622ms/1m. now devide 1meter by the result. 1m/(10.622ms/1m) = 94.144 m/s. {average speed for 5 meters} the pellet energie: e=0.5*mv². 0.5*(92.144m/s)²*0.00045kg = 1.91 Joule
    always put the mike exactly between the measuring points or you have to do more math.
    an other example, same pellets same distance:
    the weihrauch hw50 15 Jears old ( german f type with max 7.5 joule). my results:
    16.153030s-16.12422s=28.81ms; 28.81ms/5 =5.762ms; 1/5.762ms = 173.55m/s.{average speed for 5 meters} e = 6.77 joule. hope you understand my proceeding and have fun with your new zero cost chronograph :) psy303

    Comment by hotsky on 16th May 2005 | other work
    Thanks a lot Psy303 I downloaded the program you mentioned and tried it with my Skif. I works pretty good ; ). One question though what do you put for mic’s input volume? I noticed that when I leave it high at say 0.8+ it’s hard to tell what’s happening on the wave. Also I simplified the formula for calculating the velocity: >m/s = distance (m)/ Time (in sec), In your case 14.17805s minus 14.12494s = 0.05311s, So, 5m / 0.05311s = 94.144m/s. Thanks again

    Comment by psy303 on 25th May 2005 | other work
    i put 0.8 for input volume and i disabled the +20dB gain from my sound card, but every mike has another sensitivity. try the simple way and wrap your mike with some t-shirts. what happened on the wave EXACTLY, it is really hard to tell. maybe a better recording prog will help. psy303

  • B.B. Pelletier Says:

    Ray,

    Sound transducers have been used in world cup competition for decades to score targets more accurately than measuring gauges. Turning on crystal-driven accumulators with them is no problem.

    Sound being slower than light means this kind of chronograph will always have a larger error built in, but it should work okay for most applications.

    B.B.

  • Shaffer78 Says:

    I was looking at the Oehler website. They have suspended the production of the 35P. I’ve seen it for about 350 so it’s about 2 times the cost of a Chrony Gamma Master w/ printer.

  • B.B. Pelletier Says:

    Shaffer78,

    I have an Oehler 35P and I couldn’t do without it, but you are right. At a fraction of the price the Chrony give you a very capable instrument.

    B.B.

  • TAP Says:

    I have recently purchased a Madbull Airsoft Handheld Chronograph Version 1 and have been using it to not only gauge my airsoft guns but also my airgun pistols in .177 and .22 cal. I’ve compared the findings with my friends Chrony F-1 and get same results without the hassle of setup needed for the Chrony.
    Has anyone else tried this for airguns?

  • Blind Dog Says:

    A new comment to an old article, perhaps an update: Chono Connect is a free app for Droid phones, and I think iPhones have one too, that uses sound from the shot and target impact to calculate and display velocity directly. To operate it, the distances between the phone and the muzzle in both the horizontal and vertical, and distance to the target are entered. Pellet ballistic coefficient is entered, and the display gives you velocity and shot string data.

    Another home project that might be fun, is the old ballistic pendulum. By catching the projectile in media at the bottom of a mechanical pendulum, the height of the arm's swing is marked, and with known projectile weight, the velocity can be manually calculated quite accurately.
    RobT

  • B.B. Pelletier Says:

    RobT,

    Thanks for this info. I actually did a blog on the ballistic pendulum that you might be interested in. It located here:

    http://www.pyramydair.com/blog/2009/12/ballistic-pendulum.html

    B.B.

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