Muzzle velocity

Muzzle velocity

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Muzzle velocity is the speed a projectile
Projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....

 has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately 400 ft/s (121.9 m/s) to 1200 ft/s (365.8 m/s) in black powder muskets , to more than 4000 ft/s (1,219.2 m/s) in modern rifles with high-performance cartridges such as the .220 Swift
.220 Swift
The .220 Swift is a semi-rimmed rifle cartridge developed by Winchester and introduced in 1935. It was the first factory loaded rifle cartridge with a muzzle velocity of over...

 and .204 Ruger
.204 Ruger
The .204 Ruger is a centerfire rifle cartridge developed by Hornady and Ruger. At the time of its introduction in 2004, the .204 Ruger was the highest velocity commercially produced ammunition, and the only cartridge produced commercially for bullets of .204 inch/5 mm caliber.-Characteristics:The...

, all the way to 5700 ft/s (1,737.4 m/s) for tank
Tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

 guns firing kinetic energy penetrator
Kinetic energy penetrator
A kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....

 ammunition. The velocity of a projectile is highest at the muzzle and drops off steadily because of air resistance.

In conventional guns, muzzle velocity is determined by the quality (burn speed, expansion) and quantity of the propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

, the mass of the projectile, and the length of the barrel. A slower burning propellant needs a longer barrel to burn completely, but can on the other hand use a heavier projectile. A faster burning propellant may accelerate a lighter projectile to higher speeds if the same amount of propellant is used. In a gun, the pressure resulting from the combustion process is a limiting factor on projectile velocity. A balance between propellant quality and quantity, projectile mass and barrel length must be found if both safety and optimal performance is to be achieved.

Longer barrels give the propellant force more time to work on propelling the bullet. For this reason longer barrels generally provide higher velocities, everything else being equal. As the bullet moves down the bore, however, the propellant's gas pressure behind it diminishes. Given a long enough barrel, there would eventually be a point at which friction between the bullet and the barrel, and air resistance, would equal the force of the gas pressure behind it, and from that point, the velocity of the bullet would decrease.

Large naval guns will have length to diameter ratios of 38:1 to 50:1. This length ratio maximizes the projectile velocity. There is much interest in modernizing naval weaponry by using electrically driven railgun
Railgun
A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts that permit a large electric current to pass through the projectile. This current interacts...

s, which overcome the limitations noted above. With railguns, a constant acceleration is provided along the entire length of the device, greatly increasing the muzzle velocity. There is also a significant advantage in not having to carry explosive propellant and even the projectile internal charges may be eliminated due to the high velocity - the projectile becomes a strictly kinetic
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...

weapon.