In January 1964, the .223 Remington cartridge was released to the civilian market. In February 1964, the United States Air Force chose the cartridge in the form of 5.56x45mm to be used in their new M-16 rifles. The .223 was marketed to civilians as a rifle cartridge for hunting varmints and predators.
This cartridge with mild recoil would become popular across many different shooting applications and firearms disciplines. Hunters of varmints and predators were the buyers of the .223 Remington. The flat trajectory and reliable accuracy of the cartridge were appreciated by hunters who used it effectively against small vermin and medium size predators like coyotes, out to 300 yards. Some have hunted game as large as deer, but the .223 cannot used for deer hunting in several jurisdictions, as it has been noted that the bullet diameter and muzzle energy are insufficient for harvesting humanely.
The .223 Remington is popular with competitive shooters since it can be fired in Service Rifle and F-Class matches. In these matches, the contest involves shooting at ranges as great as 1,000 yards. 3-gun shooters make the .223 popular, where mild recoil allows for the light rifle with high capacity magazines to be fired for quick and precise shooting.
Many law enforcement agencies have added the .223 Remington to their cache of firearms. It rides along in patrol cars, sometimes replacing a 12 gauge shotgun when longer shots or more precision is needed. Beyond patrol duties, some departments employ the cartridge in urban sniping operations.
The bullet of the .223 Remington is actually 0.224". The bullet weighs between 36 and 77 grains. Muzzle velocities out of a rifle range between 2,700 and 3,700 feet per second, and muzzle energies are between 1,100 and 1,300 foot pounds. The .223 Remington has become one of the most purchased cartridges in the United States, so firearms manufacturers regularly expand and refine the products they have chambered for the .223.
No discussion of this cartridge would be complete without mentioning the AR-15 type rifles that are so popular. Some are chambered for .223 Remington, while others of these rifles are chambered for 5.56x45mm. The two cartridges are not interchangeable. The cases have different dimensions. If a 5.56mm cartridge is fired in a rifle chambered for .223, pressures will result that are dangerously high. Damage to the firearm and/or the shooter can result from these high pressures. However, .223 ammunition can be fired in weapons which have been chambered for the 5.56mm without ill effect.