Ballistics and Velocity
For more details on Airsoft pellet ballistics, see Airsoft pellets#Pellet ballistics.Kinetic energy is the energy that is in the pellet while it moves, and it is transferred to its target upon impact. One joule of energy will be transferred by a 0.20 g BB traveling at 100 metres per second (330 ft/s). A typical set of velocity limits for sanctioned fields in the United States on guns may be 350 F.P.S. for CQB (Close Quarters Battle), 400 F.P.S. for outdoor play with fully automatic AEG's, 450 F.P.S. for semi-auto "DMR" style AEG's, and 500-600 fps for bolt action sniper rifles, all measured with a 0.20 g BB. The speed of the BB depends on the weight of the BB and amount of kinetic energy the gun can transfer to the BB. The maximum effective range of field-legal airsoft weapons is around 100 yards (300 feet) with a highly upgraded sniper or DMR. Most airsoft guns used for field play will have an effective range of around 140–220 feet, depending on the intended role of the weapon. In California a common limit for CQB is 350 ft/s (110 m/s). Guns that have high velocities tend to have a longer range and better accuracy, also supplemented by the fact that many will also upgrade accuracy related parts, but fire rate is compromised unless a smaller spring is added (preferably 110 m/s). Furthermore, the lower velocity means that the BB will glide more, which is a good thing for indoor skirmishes, but outside the wind usually catches hold of it and spirals it out of its course.
In Ireland, Italy, and Japan the energy limit for Airsoft guns is one joule (100 m/s with a 0.20 g, 6 mm BB) regardless of the type of game play. Some UK sites allow semi-automatic-only weapons up to 400 ft/s (120 m/s) and bolt action rifles up to 500 ft/s (150 m/s). Northern Ireland has a maximum velocity of 328 ft/s (100 m/s) with 0.2 gram BB without regard to the type of weapon. 1J is the about same energy as a tennis ball being dropped from a meter and a half.
Most Airsoft guns are capable of shooting from 50 m/s (160 ft/s) to 125 m/s (410 ft/s), although it is also possible to purchase upgraded internals for some Airsoft guns that will enable the gun to shoot in excess of 550 FPS (feet per second)
The ballistics of spring or electric powered airsoft guns differ from real firearms in that a longer barrel will not always result in better accuracy. In spring/electric airsoft weapons, barrel length does not have a significant effect on accuracy. The "sweet spot" for barrel length in a spring/electric powered airsoft gun is around 400-500mm. Past that length, added barrel length will not improve accuracy. In any case, barrel quality, fps consistency, and hopup quality/design are more important factors in regard to accuracy. However, added barrel length will result in slightly increased velocity if the cylinder size and compression are appropriate for the barrel length. For example, a gun with a large cylinder and a long barrel will shoot slightly harder than a gun with a small cylinder and a short barrel(with everything else being equal). This rule will apply even for barrels longer than 500mm, if there is enough cylinder volume and air compression to propel the BB through the barrel. However, the resulting FPS increase will be hardly noticeable. The only considerable advantage of using a longer inner barrel in an aeg or spring powered gun is that it generally will make the gun quieter. Gas powered replicas function more like real firearms. In gas powered guns, added barrel length (to an appropriate degree) will result in significantly increased velocity, and increased accuracy to a degree.
Tighter bore barrels will increase velocity because there will be less space between the BB and the barrel for the air to escape through. Most stock airsoft guns have 6.05-6.08mm bore barrels, but best performance is usually seen with "tightbore" barrels. However, the tighter the bore, the more likely the chance of a BB jam, and subsequently, tightbores need to be cleaned regularly. It is generally agreed upon that a good quality 6.01-6.02mm barrel will provide the most fps, while a good quality 6.03mm barrel will provide the best compromise between power, accuracy, and ease of maintenance. The actual accuracy difference between a 6.01mm barrel and a 6.03mm barrel is debatable.
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