.223 Rem (5.56x45 mm NATO) Rifle Cartridges

The 223 Remington was developed as an experimental military cartridge for the Armalite AR-15 modular rifle. It is now a US military standard as well as an extremely popular commercial sporting round. The cartridge is nearly identical to the 222 Remington Magnum with the only difference being a slightly shorter case. Classified as a long range centerfire 22 round, its velocity is still supersonic at 500 yards. Note that while the military version (5.56x45mm NATO) is dimensionally the same, its higher pressure loads may be unsafe in civilian guns designated only for the .223 cartridge.

.223 Rem (5.56x45 mm NATO)

**See below for further reference regarding the power rankings listed in the tables above:

MV-Muzzle Velocity
Muzzle velocity when fired from a typical handgun. Measured in feet-per-second.

ME-Muzzle Energy
Muzzle energy when fired from a typical handgun. Measured in foot-pounds.

PF-Power Factor
In shooting competition the Power Factor is used to determine the competitive division in which a particular handgun/cartridge can be used. A simple calculation of the bullet's mass times its muzzle velocity.
PF = bull. mass x muzzle vel.

TKO-Taylor Knock Out Formula
Developed by big-game hunter John Howard Taylor in the 1940's. Calculates the relative effectiveness of bullets for hunting game.
TKO = (bull. mass x muzzle vel. x bull. dia.)/7000