I have had a mad, passionate love affair with adult precision airguns for over a decade. Airguns have a lot going for them. They can be shot where firearms are forbidden. They are often accurate, relatively quiet, and fun. On a cost-per-round-basis, they are extraordinarily thrifty. There is a great deal about airguns to like.
If there is one area in which airguns are deficient, it is that they are not fast. Marketing claims of high velocity to the side, I don’t know of any airgun that routinely shoots faster than 1,000 fps and is also accurate. I once shot a springer air rifle that claimed 1,500 fps velocity. It would, indeed, shoot very nearly that fast, but it was inaccurate. When I slowed down the velocity by using heavy pellets, the air rifle became quite accurate. Unlike centerfire varmint rifles, an air rifle will not launch a supersonic projectile that stays in the supersonic realm all the way to a target hundreds of yards away. Very fast rifles produce flat trajectories; air rifles do not.
Sooner or later, if you want to push the envelope of what is possible in shooting with an air rifle, you will have to deal with the arching trajectory at which airgun pellets normally travel. There are two basic approaches. The first is simply to go out, shoot at various ranges, see where the gun is shooting, and adjust accordingly. The second the scientific approach is to chronograph the air rifle with its favorite pellet, plug the resulting information into a ballistics program, and then compare the ballistics chart it produces with actual shooting results in the field. For example, you can go to http://airguns.net/trajectory.php and compute the trajectory of your pellet under the conditions that you enter. Or check out http://www.arld1.com/, demos #9 and 13 which can help you visualize your trajectory in a couple of different ways.
To get the exact velocity of your pellet(s), you will need a chronograph. For some years I have been using, and can highly recommend, the Oehler Model 35 Proof Chronograph. What makes it a proof chronograph is that there are three sky screens that work together to make sure the velocity measurements are accurate.
When a pellet passes through the front (first) sky screen, it starts the chronograph. As the pellet passes through the rearmost (third) sky screen, the main velocity measurement is calculated based on the time of flight from the first to third screens. Here’s “proof” part: the Oehler also makes a measurement as the pellet passes over the middle (second) sky screen. The chronograph then compares the two readings. If the measurement from the first to third sky screen does not agree within two percent with the measurement from the first to second sky screen (when using the two-foot rail), the displays blinks to indicate this is a suspect reading. This prevents you from accepting and using bogus information to make your shooting decisions.
In addition to the velocity for each shot, the display also will give you, after poking the appropriate buttons, a variety of data such as number of shots, high velocity, low velocity, extreme spread, and average velocity. I record the information in a notebook, but a version of the chronograph with built-in printer is also available for the less frugal.
My experience with the Oehler indicates it is a tireless workhorse, and I can cheerfully give it my heartiest recommendation without reservation. For more information, call Oehler at 1-800-531-5125.
Once you have a chronograph, what can you do with the data that you get from it? For me, there are two key things. First, you can input the pellet velocity, along with its weight, sight-in distance, and so forth, to compute the trajectory of the pellet at various distances. I have used this technique successfully to set up air rifles for field target competition. In addition, I understand that airgun varminters do similar things for setting up their rifles for clobbering pests at long range. As part of measuring the velocity of your air rifle, you can also see how consistent it is from shot to shot.
Second, you can use a chronograph to periodically test your favorite air rifles and air pistols to make sure that they are behaving well. When my favorite custom-tuned spring-piston air rifle suddenly began acting strangely, I chronographed it and found that the velocity had dropped significantly, indicating that it was time for repair.
Understand me well: if you are serious about airgunning, a chronograph is not an absolute necessity. There are certainly many excellent airgunners who do well without them. But a chronograph can be a very powerful and useful tool.
Til next time, aim true and shoot straight.
- Jock Elliott