Barrel
The tube that the projectile travels through
The barrel is the long strong tube running through all guns, whether airsoft or real-steel. It holds the projectile straight as it gains speed and ensures that it leaves the gun still travelling in the same direction. The barrel is one of the most dependant factors when improving the accuracy of a gun, although this is not particularly true with airsoft due to the inherent instability of a Ball Bearing in flight. Airsoft barrels are also smooth inside and are not rifled like most firearms.