The functionality of all our guns is tested and the muzzle velocity measured before shipping. The velocity is measured with a 0.20 g BB and the final muzzle velocity is calculated from the average of five (5) shots. In fact, the muzzle velocities you see in our online shop are approximations reported by the supplier or manufacturer. Thus, the actual muzzle velocity of your gun may differ from the approximation upwards or downwards. However, we always mark the final muzzle velocity on the maintenance and user manual provided with the gun.