The .223 Remington
In the 1950s, the 7.62x51mm NATO rifle cartridge was selected to replace the .30-06 Springfield as the standard NATO rifle cartridge. The 7.62 cartridge received a lot of criticism for being too heavy, producing too much recoil, and not allowing for a high enough rate of fire in combat. During this time, the U.S. was starting tests and research, ultimately leading to the 5.56x45mm NATO cartridge. Research started with the .222 Remington cartridge. It was quickly re-designed when it did not meet Continental Army Command’s (CONARC) velocity and penetration requirements. The case body was extended and the neck was made shorter. This became the .222 Remington special, but, to reduce confusion, was renamed to the .223. It was designed to fit the action length of the new M16 service rifle used by NATO infantry. Shortly after the U.S. Army accepted the M16, the semi-automatic version, the AR-15, became available to the general public, which made the .223 cartridge even more popular. It is used mainly in semi-automatic rifles by law enforcement, for home defense, and for varmint hunting. It is also used in survival rifles.
The 5.56x45mm NATO
The 5.56x45mm NATO was designed specifically for M16s and AR-15s. While it is derived from the .223 Remington, it is not exactly the same. Any .223 round can be fired in rifles accepting 5.56 rounds, but not the other way around. The reason for this is that rifles designed for the 5.56 round have higher tolerances for the higher pressure produced by the 5.56 round. Rifles designed for the .223 can be damaged by their lower tolerance for these higher pressures.
The 5.56x45mm replaced the 7.62x51mm, which was fired out of the M14, and the 7.62x39mm, which was fired out of the AK-47. In a series of mock-combat situations in the early 1960s with the M16, the M14 and AK-47, the Army found that the M16’s small size and light weight allowed it to be brought to action much quicker than the other two. The final conclusion was that an 8-man team equipped with the M16 and 5.56x45mm had the same fire-power as an 11 man team armed with the M14. U.S. troops were able to carry more than twice as much 5.56 ammunition as 7.62 ammunition for the same weight, which gave them a better advantage against a typical NVA (The People’s Army of Vietnam) unit armed with AK-47s.
LG Outdoors currently has ammunition for sale, including these two round sizes. This is a great time to stock up on ammunition before it gets more expensive to make and sell. Make sure you have enough ammunition for target shooting, hunting, and general home defense.