Muzzle energy is the kinetic energy of a bullet as it is expelled from the muzzle of a firearm. It is often used as a rough indication of the destructive potential of a given firearm or load. The heavier the bullet and the faster it moves, the higher its muzzle energy and the more damage it will do.
The general formula for the kinetic energy is
Calculating muzzle energy
Care must be taken when using this formula that consistent units are used.
- In SI units:
- In American engineering units:
- Mass, m, is usually given in grains and the speed, v, in feet per second but kinetic energy, Ek, is typically given in foot-pound force (abbreviated ft-lbf). Most sporting arms publications within the United States report muzzle energies in foot-pound force. If m is specified in grains and v in feet per second, the following equation can be used, which gives the energy in foot-pound force:
- When publishing kinetic energy tables for small arms ammunition, an acceleration due to gravity of 32.163 ft/s2 rather than the standard of 32.1739 ft/s2 is used. The formula therefore becomes
The bullet energy, remaining energy, down range energy and impact energy of a projectile may also be calculated using the above equations.
Typical muzzle energies of common firearms and cartridges
Example muzzle energy levels of different types of firearms Firearm Caliber Muzzle energy ft-lbf joules air gun .177 15 20 pistol .22LR 117 159 pistol 9 mm 383 519 pistol .45 ACP 416 564 rifle 5.56 × 45 mm 1,325 1,796 rifle 7.62 × 39 mm 1,527 2,070 rifle 7.62 × 51 mm 2,802 3,799 heavy .50 BMG 11,091 15,037 heavy 14.5 × 114 mm 23,744 32,000 Average muzzle energies for common pistol cartridges Cartridge Muzzle energy ft-lbf joules .380 ACP 199 270 .38 Special 310 420 9 mm Luger 350 470 .45 Colt 370 500 .45 GAP 400 540 .45 ACP 400 540 .40 S&W 425 576 .357 Sig 475 644 .357 Mag 550 750 10mm Auto 650 880 .44 Mag 1,000 1,400 .50 AE 1,500 2,000 .454 Casull 1,900 2,600 .460 SW 2,400 3,300 .500 SW 2,600 3,500
It must be stressed that muzzle energy is dependent upon the factors previously listed and that even velocity is highly variable depending upon the length of the barrel a projectile is fired from. While the above list mentions some averages, there is wide variation in commercial ammunition. A 180 grain bullet fired from .357 magnum handgun can achieve a muzzle energy of 580 foot-pounds. A 110 grain bullet fired from the same gun might only achieve 400 foot-pounds of muzzle energy, depending upon the manufacture of the cartridge. Some .45 Colt ammunition can produce 1,200 foot-pounds of muzzle energy, far in excess of the average listed above.
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.
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Look at other dictionaries:
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