How To Make A Chrono
Have you ever found yourself wonder which of your guns is strongest? Or are you just curious of what your gun's fps? Don't have a chronograph? With the help of audio software and a few other tools you will be able to get an idea of what the velocity of your gun is.
First you need audio software. The best (and easiest) ones to use are the ones that show waves and where you can record straight to the program. My personal favorite is Wavepad (click here to download a free trial) because it actually shows you the exact time you have highlighted. Another free alternative is Audacity (click here to download), which is a bit lower-tech, but gets the job done. You also need a microphone, masking tape, measuring tape, a loud target (such as a pop can), and a gun with bbs.
First, you need to set up your target. You need a backstop to catch any missed shots. Next, place one piece of masking tape where the target will be placed. Next, grab your measuring tape and measure out 15 feet (5 meters). Place masking tape there. Then, place a last piece of tape at the midway point, 7.5 feet (2.5 meters). The target will go at one end, the mic in the middle, and the gun at the other end (make sure when you shoot that the muzzle is directly on top of the tape. In the middle, connect the mic to the computer (probably a laptop) and place the computer as far away from the firing lane as the wire will allow. Place the mic on the tape, so that it does not point toward the gun or the target, but rather at an intercept.
Start up your computer and open up to (I'm going to use) Wavepad. Click the red record button on the bottom left and a small window will pop up. Click OK. In the new window, go under Recording to Device, and change it to Jack Mic (if you have a built in mic, change to Internal Mic). When you are ready to start recording, just push the new recording button. Then fire a series of shots at your target and when you're done, click the blue stop botton and close that same window.
Now on the screen you should see spikes where the audio gets louder. These are most likely your shots. Play the audio, and pause when you hear a shot (you can pause by clicking the spacebar). Once you have found the shot, highlight it by clicking and dragging with your mouse. Then zoom in a bit, so you can see the space between the shot being fired and hitting the target. Now hilghlight that space in between. Now look at the bar after the one with the play, stop, pause, etc. You should see a bar that says Start and End. This gives you the times in which the highlight starts and ends. To get the actual time, just subtract. For example, say I got 0.0427 seconds. Keep this number as well as any other for the other shots.
Now that you have a number (like 0.0427), it's time to find out your fps, using the D=rt formula. Open up Calculator and type in the distance (D) you were firing from (15 feet). Then divide that by the time (t) it took to hit the target (0.0369 sec.). 15/0.0427= about 351.289, which is roughly 350fps(r). Just remember, this isn't the exact fps, but as close as your gonna get without a real chronograph.