A New Standard: The Story of the 5.56x45mm NATO Cartridge

Good news, everyone! Considering the success and popularity of my previous blog entry titled "The Mesmerizing Tale of the 7.62x51mm NATO Cartridge," I have just been given the go-ahead to pen a sequel. Do not groan just yet. I promise to deliver another thrilling, historically-accurate account that builds on the previous entry while weaving exciting new threads that not only tells a complete story in its own right, but sets up another sequel or perhaps even a prequel. You know, just in case this is met with the very same success and popularity.

For those that are not the cultured type and do not enjoy partaking in books, comic books, television shows, movies, video games and other forms of narrative entertainment, a sequel is a continuation or expansion of some narrative that was originally presented in a previously released work. Sometimes those continuances are excellent additions to the original narrative. More often than not, they are abominations – unwatchable, unreadable or unplayable filth that exists solely to capitalize on the masses' love of a franchise. I am sure we all remember "Speed 2: Cruise Control" and I apologize for even mentioning it. But you know to expect better from me. I would never produce anything I did not believe worth producing, and this sequel is a natural progression of my previous blog entry.

If you will remember, we last left off in 1954 with the adoption of the 7.62x51mm NATO cartridge as the standard small arms cartridge for NATO countries. I made it pretty clear that the cartridge was replaced soon after its adoption, which lends itself to a sequel. So settle in and get ready for the story of the 5.56x45mm NATO cartridge. I assure you; it will be less like "Caddyshack II" and "Blues Brothers 2000" and more like "The Empire Strikes Back" and "Aliens."

An Overview of the 5.53x45mm NATO Cartridge

Sequels are very much different than the original works on which they are based. While many original works must take time to set up background information, many sequels can assume that information is already understood. I realize, however, that in addition to the fact that the information presented in my "sequel" is largely unrelated to the information presented in my previous entry, there may be new readers here. As such, I have some explaining to do.

The 5.56x45mm NATO cartridge is a rifle cartridge that was designed in the United States as a cartridge for the M16 rifle. It was derived from the commercial .223 Remington cartridge and its design spanned a number of years beginning in the late 1950s and ending in the early 1960s. After its introduction to the United States Military for use with the new M16 service rifle, it was quickly adopted by NATO as a replacement for the 7.62x51mm NATO cartridge. In terms of ballistic performance, the 5.56x45mm NATO cartridge is not quite as powerful as the NATO cartridge it replaced. A standard SS109 bullet is capable of producing approximately 1,300 foot-pounds of energy, though its muzzle velocity is much higher than that of the 7.62x51mm NATO cartridge and has been observed to travel at speeds of approximately 3,100 fps. It also has a tendency to yaw and fragment in tissue after impacts that occur at extremely high velocities, which is believed to sometimes result in hydrostatic shock. This aspect of its performance is also the subject of much debate and criticism, though that is a topic best reserved for another day.

As noted, the 5.56x45mm NATO cartridge was derived from the commercial .223 Remington cartridge. These two cartridges, while possessing dimensions that are very similar, are not identical. Though it might be safe to fire .223 Remington cartridges from a rifle chambered in 5.56x45mm NATO, the Sporting Arms and Ammunition Manufacturers' Institute warns specifically about the safety of firing 5.56x45mm NATO cartridge from rifles with a chambering other than 5.56x45mm NATO.

And now that we know more than ever about the 5.56x45mm NATO cartridge, it is about time we move on to some information regarding its development.

The Development of the 5.56x45mm NATO Cartridge

Though I never mentioned in in my previous entry, the 7.62x51mm NATO cartridge was not always popular and never universally praised. After all, I cannot show all of my cards at once. Prior to the selection of the 7.62x51mm NATO cartridge, the British army was working on an intermediate cartridge known as the .280 British cartridge – what they had hoped would become the standard small arms NATO cartridge. Its development was led by the very same criticisms of the 7.62x51mm NATO cartridge that would eventually lead the development of the 5.56x45mm NATO cartridge. The 7.62x51mm NATO cartridge was, the British felt, too powerful for controlled automatic fire. It produced too much recoil and its hefty overall weight was less-than-ideal. Ironically, the United States thought the .280 British cartridge underpowered. A few years later, they began work on what would become the 5.56x45mm NATO cartridge.

In the late 1950s, several arms manufacturers, including ArmaLite, began individual small caliber, high velocity assault rifle experiments with the .222 Remington cartridge – a cartridge that was quickly ruled out as a possible contender for service due to its limited powder capacity. ArmaLite reached out to Remington Arms seeking a cartridge similar to the .222 Remington cartridge but with a longer case body and therefore greater capacity for propellant powders. The new cartridge was initially known as the .222 Remington Special. Shortly after, in an effort to avoid confusion with other manufacturers seeking similar cartridges, the .222 Remington Special was renamed the .223 Remington cartridge. It was soon after adopted by the United States Military as the 5.56x45mm cartridge for use with the new M16 service rifle, which was developed alongside the development of the cartridge. Again, that is a long and fascinating story that begs too much time to be discussed here.

The new cartridge was desirable in part due to its reduced weight as compared to both the 7.62x51mm NATO cartridge and the 7.62x39mm cartridge. When carrying a load of 10 kg worth of ammunition, troops were able to carry over twice as much 5.56x45mm ammunition as they would 7.62x51mm ammunition. At a cap of 10 kg, soldiers could carry 33 M16 magazines for a total of 660 rounds of ammunition and only 14 M14 magazines for a total of 280 rounds.

The success of the 5.56x45mm cartridge with the United States Military led it to be adopted as a standard small arms cartridge for NATO countries under Standardized Agreement (STANAG) 4172. To this day, it remains the standard small arms cartridge for NATO countries.

Keepshooting.com and the 5.56x45mm NATO Cartridge

And so we come to the part of the story where I introduce you to our 5.56x45mm NATO/.223 Remington ammunition section. These cartridges are two of the most widely-used cartridges in the United States. They are popular with rifles like the AR-15 and the Ruger Mini-14. That said, these cartridges are relatively inexpensive and are popular with target shooters. In an effort to supply our customers with the widest selection and the best prices around, Keepshooting.com has decided to carry 5.56x45mm NATO and .223 Remington ammunition – we would be fools not to. If you have an AR-15, you may be interested in our PMC X-Tac 5.56 ammunition. Each box contains 20 rounds M193 bullets. We are also stocking Federal XM193 5.56 ammunition as frequently as possible. And if your rifle is chambered in .223 Remington, check out our Wolf Polyformance .223 Remington ammunition.