Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to[1] the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle).[2] Firearm muzzle velocities range from approximately 120 m/s (390 ft/s) to 370 m/s (1,200 ft/s) in black powder muskets,[3] to more than 1,200 m/s (3,900 ft/s)[4] in modern rifles with high-velocity cartridges such as the .220 Swift and .204 Ruger, all the way to 1,700 m/s (5,600 ft/s)[5] 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 8,500 m/s (28,000 ft/s).[6] FPS (feet per second) and MPH (miles per hour) are the most common American measurements for bullets. Several factors, including the type of firearm, the cartridge, and the barrel length, determine the bullet's muzzle velocity.[7]