A Brief History Of The 5.56 NATO Round

The 5.56 NATO round has been in service since the late 1960's, and was developed with the M16.
During the Korean war, we realized the 30/06 cartridge was an adequate man stopper, but the heavy recoil made it hard for our troops to shoot their M1 Garands as fast as they could effectively. Lots of times in the Korean war, our troops would have to empty and reload their Garands as fast as they could just to hold their ground.

This lead to the development a smaller caliber rifle that would be much easier to control on semi and fully automatic. This contract opportunity was seized by Armalite, with the development of the early M16.
This new M16 was issued in large numbers to our conflict in the Vietnam war, but did not receive good reviews at all from the troops. This is due not to design flaws of the rifle itself, but of the round.

The round that was issued for the Vietnam war used a brick type powder, this lead to extreme fouling in the M16's and lead to costly jams on the field. Our troops were not even issued cleaning kits at the time, so soldiers would be seen wiping the fouling out of the chamber with their socks. The different powder choice led to a slightly increased velocity, but the costs were obviously great.

The 5.56 cartridge's most common weight bullet is 55 grains, this little lightweight bullet moves at approximately 3000 FPS. This light little bullet REQUIRES that extremely high velocity to retain its deadly capabilities.

Another use for a lower caliber rifle cartridge is the revelation that killing a enemy soldier causes a lot less confusion then wounding one. When you hit something with the 30/06 round, it died. The point of the 5.56 is to have it keep the individual alive long enough to cause confusing against the enemy, but still have them die.

Shortly after, the Russians saw we changed to the 5.56 NATO round, and developed its own version. The Ak74. The Ak74 uses a similar 5.45 round, and has similar characteristics. The Kalashnikov's did not want to build a lower caliber version of the AK, for they believed the 7.62x39 caliber cartridge was superior for all modern battlefield conflicts. But they did it anyway.

The M16 was designed with around a 22 inch barrel, as such, the round. So, the 5.56 round is designed to burn all of its powder and optimal velocity in that 22 inch barrel. The civilian market has adopted a 16" Barrel as it is as short as the ATF will let us have it. Though the 22 inch barrel is the most optimal barrel length for this round.

The civilian market picked up the AR15 around the 80's, with it eventually becoming the most common Modern Sporting Rifle. Remington developed the .223 round from their popular .222. Dimensionally, the .223 is exactly the same as the 5.56, but the 5.56 is loaded to a higher pressure. This is why it is not recommended that you shoot 5.56 in a .223 chamber, but I have never experienced a problem doing this.

The 5.56 is now the most common caliber for a sporting and hunting rifles, and is still growing. Its great for Varmit hunting, and is used in our Military applications exclusively still in the form of M4 carbines.