Muzzle velocity is the speed a
projectile has at the moment it leaves the
muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets, to more than in modern rifles with high-performance cartridges such as the
.220 Swift and
.204 Ruger, all the way to for
tank guns firing
kinetic energy penetrator ammunition. To simulate orbital debris impacts on spacecraft, NASA launches projectiles through
light-gas guns at speeds up to . The velocity of a projectile is highest at the muzzle and drops off steadily because of air resistance. Projectiles traveling less than the
speed of sound (about 340 m/s or 1115 feet/s in dry air at sea level) are subsonic, while those traveling faster are supersonic and thus can travel a substantial distance and even hit a target before a nearby observer hears the "bang" of the shot. Projectile speed through air depends on a number of factors such as
barometric pressure,
humidity,
air temperature, and
wind speed.