Muzzle energy

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Muzzle energy is the measurement of the kinetic energy of a bullet as it is expelled from the barrel of a firearm.

The general formula for the kinetic energy in a coherent system of units, including SI and cgs systems, and the gravitational foot-pound-second and the absolute foot-pound-second system, is:

E_t = .5 • m • v²

In SI, mass m is in kilograms and velocity v is in metres per second, given kinetic energy _transitional E_t in joules.

For non-SI units of measure, a conversion factor must be added. For example, to get muzzle energy where

E_t is the muzzle energy of bullet (in foot-pound force)

v is the velocity of bullet (in feet per second)

m is the mass of bullet (in grains)

The formula is

E_t = m • v² / 2 • 32.1739 • 7000

Other values are possible, depending on how the local acceleration of gravity (g) effects the dimensional constant (g_c). The dimensional constant of 32.1739 lb_m • ft / lb_f • s² is derived from the non-SI unit of measure from the English Engineering System.
Most if not all sporting arms publication within the United States, when publishing kinetic energy tables for small arms ammunition, use a dimensional constant of 32.163 lb_m • ft / lb_f • s².
The Standard acceleration of gravity (g_n) of 32.1739 ft / s² (exactly), is from the non-SI unit of measure within the English Engineering System.

[edit] Calculations of Muzzle Energy

Typical muzzle energy levels of different types of firearms for both SI units of measure in joules and the non-SI units of measure form the English Engineering System in foot-pound force are:

Firearm	Caliber	Muzzle energy
Firearm	Caliber	(ft • lb_f)	(J)
air gun	.177	5	7
rifle	.22LR	100	135
rifle	5.56x45 mm	1200	1550
pistol (semi-auto)	9 mm	350	540

Average muzzle energies for common pistol cartridges:
.355 Luger-----350 ft • lb_f *9mm Luger

.357 Sig-------475 ft • lb_f

.357 Mag-------550 ft • lb_f

.38 Special----200 ft • lb_f

10mm Auto------425 ft • lb_f *.400 Auto

.40 SW---------425 ft • lb_f *Smith and Wesson

.44 Mag--------740 ft • lb_f

.45 GAP--------350 ft • lb_f *Glock Automatic Pistol

.45 ACP--------370 ft • lb_f *Automatic Colt Pistol

.45 Colt-------370 ft • lb_f *45 "Long" Colt

.454 Casull----1900 ft • lb_f

.460 SW--------2400 ft • lb_f

.50 AE---------1500 ft • lb_f *Action Express

.500 SW--------2600 ft • lb_f

                   MUZZLE ENERGY FORMULA FOR NON-SI UNITS

ME = Muzzle Energy in foot-pound force.

450434.6 = A term in the formula which is two times the dementional constant times a convertion factor to set the equation equal to pounds = 2 • 32.1739 • 7000 = 450434.6.

m = The weight of the bullet in grains.

v = The velocity of the bullet in feet per second.

                      ME = mv²/450434.6

The bullet energy, remaining energy, down range energy and impact energy of a projectile may also be calculated using any of the above equations (formulae).