Muzzle velocity is the speed of a projectile at the moment it leaves
the muzzle of a gun. Muzzle velocities range from approximately
120 m/s (390 ft/s) to 370 m/s (1,200 ft/s) in
black powder muskets, to more than 1,200 m/s
(3,900 ft/s) in modern rifles with high-performance cartridges
such as the
.220 Swift and .204 Ruger, all the way to 1,700 m/s
(5,600 ft/s) 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).
2 Conventional guns
4 Categories of velocity
5 See also
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. Some
high-velocity small arms have muzzle velocities higher than the escape
velocities of some Solar System bodies such as Pluto and Ceres,
meaning that a bullet fired from such a gun on the surface of the body
would leave its gravitational field; however no arms are known with
muzzle velocities that can overcome Earth's gravity (and atmosphere)
or those of the other planets or the Moon.
While traditional cartridges cannot generally achieve a Moon escape
velocity (or higher) due to modern limitations of action (firearms)
and gunpowder, a 1 gram (15.4324 grain) projectile was accelerated to
velocities exceeding 9,000 m/s (~30,000 ft/s) at Sandia National
Laboratories in 1994. The gun operated in two stages. First, burning
gunpowder was used to drive a piston to pressurize hydrogen to 10,000
atm. The pressurized gas was then released to a secondary piston,
which traveled forward into a shock-absorbing "pillow", transferring
the energy from the piston to the projectile on the other side of the
This discovery might indicate that future projectile velocities
exceeding 1,500 m/s (~4921 ft/s) have to have a charging, gas-operated
action that transfers the energy, rather than a system that uses
primer, gunpowder, and a fraction of the released gas. One should also
note that a
.22 LR cartridge is approximately three times the mass of
the projectile in question. This may be another indication that future
arms developments will take more interest in smaller caliber rounds,
especially due to modern limitations such as metal usage, cost, and
cartridge design. In a side by side comparison with the .50 BMG, the
15.4324 grain titanium round of any caliber released almost 28 times
the energy of the .50 BMG, with only a 27% mean loss in momentum.
Energy, in most cases, is what is lethal to the target, not momentum.
In conventional guns, muzzle velocity is determined by the quality
(burn speed, expansion) and quantity of the propellant, 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.
Propellant quality and quantity, projectile mass, and barrel length
must be balanced to achieve safety and optimal performance.
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.
Rifled barrels have twists in them that spin the football-shaped
bullet so that, much like a football, it remains stable in flight. The
longer the barrel the better the rotation and with that, the better
the accuracy of the weapon. If you examine shot groups from a 2 inch
barrel, a 4 inch barrel, and a 6 inch barrel, you’ll find tighter
groups with the longer barrels.
When a bullet is fired from a handgun with a 2 inch barrel, the bullet
only travels 2 inches before it leaves the barrel. Once it leaves the
barrel, the gas pushing it out stops being a factor in the bullet’s
propulsion. In fact, in some instances, the powder may not even be
fully burned at that point. So the muzzle velocity of a 2 inch barrel
is less than that of a 4 inch barrel.
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
railguns, 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 weapon.
Categories of velocity
United States Army
United States Army defines different categories of muzzle velocity
for different types of weapons:
Less than 762 m/s (2,500 ft/s)
Between 914 m/s (3,000 ft/s) and 1,067 m/s
Greater than 1,067 m/s (3,500 ft/s)
Between 472 m/s (1,550 ft/s) and 1,021 m/s
Greater than 1,021 m/s (3,350 ft/s)
Between 1,067 m/s (3,500 ft/s) and 1,524 m/s
Greater than 1,524 m/s (5,000 ft/s)
^ "Muzzle Velocity". Archived from the original on 15 May 2010.
Retrieved 9 June 2011.
^ "The Accuracy of Black Powder Muskets" (PDF). Retrieved 9 June
^ "Speed of a Bullet". Retrieved 10 December 2013.
Tank Gun KE Ammunition". Retrieved 9 June 2011.
Hypervelocity Test Laboratory". Archived from the original
on 30 July 2014. Retrieved 29 July 2014.
^ Brown, Malcom. "Fastest Gun on Earth: Goals Go Beyond Planet".
www.nytimes.com. NY Times. Retrieved 23 March 2018.
^ Xiao, Haile. "Which one makes a bullet dangerous, its kinetic energy
or its momentum?". www.quora.com. Quora. Retrieved 23 March
^ a b "The Rifle Barrel". Retrieved 9 June 2011.
^ a b "What does a longer barrel mean for a gun and why is this? -
Quora". www.quora.com. Retrieved 2017-11-02.
^ "Dictionary of
United States Army
United States Army Terms"