 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Muzzle energy" – news ·newspapers ·books ·scholar ·JSTOR(December 2009) (Learn how and when to remove this message) |
Muzzle energy is thekinetic energy of abullet as it is expelled from themuzzle 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 thefaster it moves, the higher its muzzle energy and the more damage it will do.
The general formula for the kinetic energy iswherev is thevelocity of the bullet andm is themass of the bullet.
Although both mass and velocity contribute to the muzzle energy, the muzzle energy is proportional to the mass while proportional to thesquare 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 increasesfour times. In theSI system the aboveEk will be in unitjoules if the mass,m, is inkilograms, and the speed,v, is inmetres per second.[1]
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.[2] Also the muzzle energy is only an upper limit for how much energy is transmitted to the target, and the effects of aballistic trauma depend on several other factors as well. There is wide variation in commercial ammunition. A 180 gr (12 g) bullet fired from.357 Magnum handgun can achieve a muzzle energy of 580 ft⋅lbf (790 J). A 110 gr (7.1 g) bullet fired from the same gun might only achieve 400 ft⋅lbf (540 J) of muzzle energy, depending upon the manufacturer of the cartridge. Some.45 Colt +P ammunition can produce 1,200 ft⋅lbf (1,600 J) of muzzle energy.[citation needed]
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 indicates the various approaches taken.Firearms regulation in the United Kingdom is a complicated example, but is demarked by muzzle energy as well as barrel length and ammunition diameter.
Some jurisdictions also stipulateminimum muzzle energies for safe hunting. For example, inDenmark rifle ammunition used for hunting the largest types of game there such asred deer must have a kinetic energyE100 (i.e.: at 100 m (110 yd) range) of at least 2,700 J (2,000 ft⋅lbf) and a bullet mass of at least 9 g (140 gr) or alternatively anE100 of at least 2,000 J (1,500 ft⋅lbf) and a bullet mass of at least 10 g (150 gr).[3]Namibia specifies three levels of minimum muzzle energy for hunting depending on the size of the game, 1,350 J (1,000 ft⋅lbf) for game such asspringbok, 2,700 J (2,000 ft⋅lbf) for game such ashartebeest, and 5,400 J (4,000 ft⋅lbf) forBig Five game, together with a minimum caliber of 7 mm (0.28 in).[4]
InGermany,airsoft guns with a muzzle energy of no more than 0.5 J (0.37 ft⋅lbf) are exempt from thegun law,[5] whileair guns with a muzzle energy of no more than 7.5 J (5.5 ft⋅lbf) may be acquired without afirearms license.[6]
Mainland China uses a varied concept of "muzzle ratio kinetic energy" (Chinese:枪口比动能), which is thequotient (ratio) of the muzzle energydivided by theborecross sectional area, to distinguish genuine guns from "imitation"replicas liketoy guns. TheMinistry of Public Security unilaterally introduced the concept in 2008 leading up to theBeijing 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 (particularlyairsoft) tobecome illegal overnight, as almost allairsoft guns shooting a standard 0.20 g (3.1 gr)6 mm (0.24 in) pellet have amuzzle velocity over 76 m/s (250 ft/s), which translates to more than 0.58 J (0.43 ft⋅lbf) of muzzle energy, or 2.0536 J/cm2 of "ratio energy". For comparison astandard baseballchangeup thrown at 34 m/s (110 ft/s) has 1.951 J/cm2 of "ratio energy" which also exceeds the 1.8 J/cm2 of a real firearm while afastball can reach over 3.5 J/cm2 or nearly double the level of a real firearm. The subsequent crackdowns bylocal 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.