Feet per second, abbreviated FPS, is the most common U.S. measurement for an airsoft gun's muzzle velocity. Airsoft guns can fire anywhere between 100 and 700 FPS. However, most airsoft guns sold do not exceed 500 FPS without heavy modification by the purchaser. Most airsoft guns on the market will shoot between 200 and 400 FPS out of the box. Many airsoft leagues and airsoft facilities place a limit on muzzle velocity ranging anywhere from 300 to 500 FPS. This is done to ensure player safety and guarantee a level playing field. So if you are joining an airsoft team or want to take your new airsoft gun into competition be sure your muzzle velocity falls within the limits. A simple chronograph can be used to determine muzzle velocity on your own. Chronographs can vary in price although accurate models can be found for a reasonable sum. Some airsoft enthusiasts have used home made chronographs by using two computer microphones and two sheets of paper a set distance apart. The idea is to set up the mics so they will hear when the airsoft BBs break through the two sheets of paper and then using the computer audio software determine the time between the two rips. The distance between the sheets of paper is then divided by the time between the rips to determine the gun's muzzle velocity. However, this method can highly unreliable as it is subject to a number of possible outside effectors.