Muzzle velocity refers to the speed at which a projectile, such as a bullet, exits the barrel of a firearm. It is typically measured in feet per second (fps) or meters per second (m/s). Higher muzzle velocity can lead to greater accuracy and distance, as the projectile travels faster and is less affected by gravity and air resistance. Factors that influence muzzle velocity include the type of firearm, the length of the barrel, and the amount and type of gunpowder used in the cartridge. Different calibers, such as 9mm or .223 Remington, will also have varying muzzle velocities, affecting their performance in different shooting scenarios.