Muzzle energy is the
kinetic energy
In physics, the kinetic energy of an object is the energy that 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 acc ...
of a
bullet as it is expelled from the
muzzle of a firearm. Without consideration of factors such as aerodynamics and gravity for the sake of comparison, muzzle energy is used as a rough indication of the destructive potential of a given firearm or cartridge. The heavier the bullet and especially the
faster it moves, the higher its muzzle energy and the more damage it will do.
Kinetic energy
The general formula for the kinetic energy is
:
where
:''v'' is the
velocity
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...
of the bullet
:''m'' is the
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
of the bullet.
Although both mass and velocity contribute to the muzzle energy, the muzzle energy is proportional to the mass while proportional to the ''square'' of the velocity. The velocity of the bullet is a more important determinant of muzzle energy. For a constant velocity, if the mass is doubled, the energy is doubled; however, for a constant mass, if the velocity is doubled, the muzzle energy increases ''four'' times. In the
SI system
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
the above ''E''
k will be in unit
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...
if the mass, ''m'', is in
kilogram, and the speed, ''v'', is in
metre per second.
Typical muzzle energies of common firearms and cartridges
Muzzle energy is dependent upon the factors previously listed, and velocity is highly variable depending upon the length of the barrel a projectile is fired from. Also the muzzle energy is only an upper limit for how much energy is transmitted to the target, and the effects of a
ballistic trauma depend on several other factors as well. There is wide variation in commercial ammunition. A bullet fired from .357 magnum handgun can achieve a muzzle energy of . A bullet fired from the same gun might only achieve of muzzle energy, depending upon the manufacture of the cartridge. Some .45 Colt ammunition can produce of muzzle energy.
Legal requirements on muzzle energy
Many parts of the world use muzzle energy to classify guns into categories that require different categories of licence. In general guns that have the potential to be more dangerous have tighter controls, while those of minimal energy, such as small air pistols or air rifles, require little more than user registration, or in some countries have no restrictions at all.
Overview of gun laws by nation
Gun laws and policies, collectively referred to as firearms regulation or gun control, regulate the manufacture, sale, transfer, possession, modification, and use of small arms by civilians. Laws of some countries may afford civilians a right t ...
indicates the various approaches taken.
Firearms regulation in the United Kingdom
In the United Kingdom, access by the general public to firearms is subject to some of the strictest control measures in the world. However, fulfilment of the criteria and requirements as laid out by the laws results in the vast majority of fir ...
is a complicated example, but is demarked by muzzle energy as well as barrel length and ammunition diameter.
Some jurisdictions also stipulate ''minimum'' muzzle energies for safe hunting. For example, in Denmark rifle ammunition used for hunting the largest types of game there such as
red deer
The red deer (''Cervus elaphus'') is one of the largest deer species. A male red deer is called a stag or hart, and a female is called a hind. The red deer inhabits most of Europe, the Caucasus Mountains region, Anatolia, Iran, and parts of we ...
must have a kinetic energy ''E''
100 (i.e.: at 100 m range) of at least 2700 J and a bullet mass of at least 9 g or alternatively an ''E''
100 of at least 2000 J and a bullet mass of at least 10 g. Namibia specifies three levels of minimum muzzle energy for hunting, 1350 J for game such as
springbok
The springbok (''Antidorcas marsupialis'') is a medium-sized antelope found mainly in south and southwest Africa. The sole member of the genus ''Antidorcas'', this bovid was first described by the German zoologist Eberhard August Wilhelm ...
, 2700 J for game such as
hartebeest
The hartebeest (; ''Alcelaphus buselaphus''), also known as kongoni or kaama, is an African antelope. It is the only member of the genus ''Alcelaphus''. Eight subspecies have been described, including two sometimes considered to be independ ...
and 5400 J for
big game, together with a minimum caliber of 7 mm.
In Germany
airsoft guns with a muzzle energy of no more than 0.5 J are exempt from the
gun law
Gun laws and policies, collectively referred to as firearms regulation or gun control, regulate the manufacture, sale, transfer, possession, modification, and use of small arms by civilians. Laws of some countries may afford civilians a right to ...
, while
air guns with a muzzle energy of no more than 7.5 J may be acquired without a
firearms license.
Mainland China
"Mainland China" is a geopolitical term defined as the territory governed by the People's Republic of China (including islands like Hainan or Chongming), excluding dependent territories of the PRC, and other territories within Greater China. ...
uses a varied concept of "muzzle ratio kinetic energy" ( zh, 枪口比动能), which is the
quotient
In arithmetic, a quotient (from lat, quotiens 'how many times', pronounced ) is a quantity produced by the division of two numbers. The quotient has widespread use throughout mathematics, and is commonly referred to as the integer part of a ...
(
ratio
In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
) of the muzzle energy
divided by the
bore cross sectional area, to distinguish genuine guns from "imitation"
replicas like
toy gun
Toy guns are toys which imitate real guns, but are designed for recreational sport or casual play by children. From hand-carved wooden replicas to factory-produced pop guns From Gilroy Gardens and cap guns, toy guns come in all sizes, price ...
s. The
Ministry of Public Security unilaterally introduced the concept in 2008 leading up to the
Beijing Olympic Games, dictating that anything over 1.8 J/
cm2 to be defined as real firearms. This caused many existing toy gun products on the Chinese market (particularly
airsoft
Airsoft is a team game in which participants eliminate opposing players by tagging them out of play with spherical plastic projectiles shot with mock air weapons(usually powered by an electronic motor) called airsoft guns.
Although similar ...
) to
become illegal overnight, as almost all
airsoft gun
Airsoft guns are replica toy guns used in airsoft sports. They are a special type of low-power smoothbore air guns designed to shoot non-metallic spherical projectiles (pb) often colloquially (but incorrectly) referred to as " BBs", which are ...
s shooting a standard 0.20 gram
6 mm pellet have a
muzzle velocity over , which translates to more than of muzzle energy, or 2.0536 J/cm
2 of "ratio energy". For comparison a
standard baseball changeup
A changeup is a type of pitch in baseball and fastpitch softball.
The changeup is a staple off-speed pitch often used in a pitcher's arsenal, usually thrown to look like a fastball but arriving much more slowly to the plate. Its reduced speed ...
thrown at has 1.951 J/cm
2 of "ratio energy" which also exceeds the 1.8 J/cm
2 level of a real firearm while a
fastball
The fastball is the most common type of pitch thrown by pitchers in baseball and softball. " Power pitchers," such as former American major leaguers Nolan Ryan and Roger Clemens, rely on speed to prevent the ball from being hit, and have thr ...
can reach over 3.5 J/cm
2 or nearly double the level of a real firearm. The subsequent crackdowns by
local law enforcement led to many seizures, arrests and prosecutions of individual owners for "trafficking and possession of illegal weapons" over the years for weapons that were previously permitted.
See also
*
Free recoil
*
Muzzle velocity
*
Power factor (shooting sports)
Power Factor (PF) in practical shooting competitions refers to a ranking system used to reward cartridges with more recoil. Power factor is a measure of the momentum of the bullet (scaled product of the bullet's mass and velocity), which to some ...
Resources
*Edward F. Obert, ''Thermodynamics'', McGraw-Hill Book Co., 1948.
*Mc Graw-Hill encyclopedia of Science and Technology, volume ebe-eye and ice-lev, 9th Edition, Mc Graw-Hill, 2002.
References
{{DEFAULTSORT:Muzzle Energy
Ammunition
Ballistics