Home Made Chronograph Guide 
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With this guide I will help you make a simple chronograph with items that you can find in most households. Based on how carefully you take your results you can yield very precise results. I won't say that this method is accurate(as I don't have a professional grade chronograph to compare it to), but the results are very consistant and can serve as a quick and easy way to compare your guns against each other or with different internal setups.
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YOU ALSO NEED
(Open Source sound recording utility)
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How it works:
The method of "clocking" your gun is based on the time it takes for a bb to travel from the moment you fire a shot, to the moment that the bb impacts an object at a known distance. Hence the term Feet Per Second. FPS.
1. Find an area with 5-15 feet of space near your computer to shoot.(guaging the speed closer than 10 feet is difficult - but yields an FPS close to the actual muzzle velocity)
2. Setup a solid target, or an object that will make a loud sound when the bb hits it. (Not your friend. We are looking for something like a popcan.)
3. With the measuring tape measure how far away you intend to shoot
4. Position the microphone to pick up both the sound of a shot being fired, and the bb hitting the target.
5. Load up
6. Cock your gun
7. Wait for silence(tell your friend to stop talking) and Hit the record button
8. From the measured distance - fire your gun.
9. Stop recording.
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Calculating the FPS:
All we are going to do at this point is to find the time between these 2 peaks, of these 2 sounds.
To do this all you need to do is select the space between the two waves with the mouse, and on the bottom it will show the time between the two waves.
FPS = Distance/Time
In this example, I used a distance of 22.5 feet and got a time of .085682 seconds
FPS = 22.5 feet /.085682 seconds = 262 FPS
That's it!
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Summary, Extra Notes
With this calculation we are merely calculating the average FPS over the distance we measured. Not the true muzzle velocity.
If you do this test, post your results!
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Tips:
*To get precise results, select only the sound of the shot and the initial hit (first 2 waves) and trim everything around it. You should also note that some microphones will pick up the sound of you pulling your trigger, don't mistake that for the sound of the shot. Zoom in and select the distance from the highest point from the shot, and ricochet to get consistent results.
*Place the microphone in the middle between the popcan and the firing position, this negates the speed of sound from the result.
*Also be aware of the position of your gun in relation to the distance you measured on the floor. If you are holding your gun 3 feet over the line, you will be skewing your results.
*If you want to get an approximate muzzle velocity(what they guage for competition) try the test from a closer distance(like 5 feet). If you want consistant easy results for comparing one gun/configuration to another, use a larger test range.
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My Results:
(From 22.5 Feet)
KWC Desert Eagle Spring (Ultra-Grade)
- 0.20g BB = 187 FPS
- 0.12g BB = 255 FPS (average)
Tokyo Marui Spring MP5-SD3 (old)
- 0.20g BB = 180 FPS
- 0.12g BB = 205 FPS
20$ Desert Eagle - unknown brand from airsplat 3 years ago.
-0.20g BB = 167 FPS
-0.12g BB = 190 FPS
The other noname springers from walmart clocked in around 140-175 FPS - note these were the ones that were claimed to shoot "290 FPS" on the box. Where in reality it was almost half what was advertised. Confirming the fact that they are in fact shit, but we knew that already
