Posted by on 1/26/2022 to
If you own an AR-15 there is a good chance that you are using either .223 Remington or 5.56 NATO calibers. Among the many likely reasons for this is that these two calibers are calibers made specifically for the AR-15 platform, and are still by far the most popular. When you compare them side by side they are almost identical. There may be very small differences between manufacturers, but not so much you can see it with the naked eye. The main differences between the two are that the 5.56 is a little bit sturdier and can have about a .125 inch longer throat, making it that much longer. The 5.56mm is the metric system counterpart to the .223. It’s based on the bullet base diameter, so it’s 5.56 millimeters or .223 of an inch, same size, different measurement system. The reason for the different names is because the military went to the more logical metric system sometime between the two different ammunitions being made. Also, since they are different, it is good to have some way to distinguish that. When looking at them the easiest way to tell them apart is by looking at the bottom. .223 REM is engraved, while on the 5.56 you will see a cross in a circle. You can use the exact same magazines for either caliber. You can use these similar yet different calibers in the same gun, though not universally. You must use caution and knowledge when doing so to keep you and your firearms safe. .223 can be used in both but 5.56 should only be used in that caliber chamber. .223 ammunition should be military grade, otherwise it could be meant for bolt action rifles which can lead to issued where the bullet gets pushed into the casing.
Both the .223 and the AR-15 were the result of the U.S. Military’s project to create a high-velocity yet small-caliber service rifle. It was the first official ammunition for the AR-15. It is a great low-caliber cartridge made for a great gun. The .223 is a high-velocity version of a .22 and is very similar to the 222 magnum cartridge. The cartridge was smaller in size compared to the previous official cartridge, the 7.62mm x 39, yet had great results in damage output. The small size of this caliber has many advantages. The main benefit for the military is that it is low weight while having a good damage output. This meant that it was easier to carry and troops could carry more of the ammunition. The reduced recoil is also a great advantage and can be lessened further with a muzzle device and its buffer system. This reduced recoil allowed troops to handle their weapons while in fully automatic mode. The smaller amount of gunpowder also reduced noise though it is still loud enough that you should use ear protection. .223 is known for its accuracy, even at relatively long distances, due to its high velocity. This caliber is no longer extensively used by the military since the higher velocity 5.56 took its place, yet it is still a popular cartridge for the #1 civilian sporting rifle and great for game hunting, as well as sport shooting.
The 5.56 NATO came later and was also originally made for the military. It does all that the .223 does, yet with even higher velocity. It achieves this higher velocity with subtle differences like a steeper angled shoulder along with a longer throat, which allows for more gun powder in its casing. This causes more pressure in the chamber and more velocity as it exits the barrel. Since high velocity means greater kinetic energy, it causes more damage when it hits its target. The NATO part refers to a standard created by the Northern Atlantic Treaty Organization. This is a group of countries, of which the U.S. is one, that are allied with one another. The standardization of the 5.56 NATO allows troops of these countries to reliably share ammunition with one another.
Firing .223 in a gun chambered for 5.56 is fine, accuracy may not be as good as if it was fired from a matching chamber, but it shouldn’t be dangerous. This is because the chamber is larger, so it can handle the heat and pressure of the extra gunpowder. The shape of the chamber makes the .223 fit slightly less snugly, once again due to that different shoulder angle, causing it to be slightly less accurate. Unless you’re some marksmanship beast though, you probably won’t notice the difference. Since both calibers are high velocity, they are also good to use for pretty long ranges. The effective range of both is around 400 - 500 yards. Using a 5.56 cartridge in a gun chambered for .223 may be dangerous due to the higher pressure. The chamber of the .223 is simply not built to handle the more powerful 5.56. Besides having a little extra room, the 5.56 chamber is also much stronger and more durable and can handle the extra pressure caused by the greater amount of gunpowder.
Being able to fire both calibers in the same gun is convenient, and can be less expensive. A box of .223 Remington is often less expensive than a box of 5.56 NATO, but not always. Sometimes the prices are quite close to each other, other times one can be twice as much as the other. With all that fluctuation it can be nice to just go ahead and get the one that is cheapest at the time. .223 can be a lot easier to come by since it is marketed directly to everyone whereas the 5.56 was made originally for the military, and when you can find and buy it, it is usually surplus. Still, both rounds have their different roles and it is nice to be able to go back and forth between them. Which is why it’s so great that the .223 Wylde was created. This is a new chamber that has been introduced which makes it so you don’t have to compromise,
The .223 Wylde chamber is stronger than your average .223 chamber. The external dimensions and leade angle are the same as a normal 5.56 NATO chamber, however, it has the leade diameter of .223. This makes the chamber large enough to handle hotter 5.56 NATO loads, and the diameter of the leade small enough for a tight and controlled gas expansion that will make .223 Remington accurate. The best of both worlds.
It is important to note that there is no such thing as .223 Wylde ammunition. Rather the .223 Wylde chamber will allow for safe and accurate firing for both the .223 Remington and 5.56 NATO. Currently, no other similar-sized cartridges are rated to safely use in the .223 Wylde. Calibers such as the .218 Bee, .219 Zipper, .220 Swift, .221 Fireball, .224 Weatherby Varmintmaster, or the .225 Winchester might all use a similar-sized bullet, but the cartridge itself is different. There is still a lot of variety with these two calibers, especially when you consider the different grains or bullet weights available. Beyond that, different ammunition types like hollow point and full metal jacket show just how versatile the 223 and 5.56 cartridges are.
Notable differences:
.223 Winchester:
Civilian
About 55,000 PSI
Shorter throat
Made with lower pressure in mind
Can be used in all 3 chambers
Can be identified by 223 REM inscribed on the case
Usually cheaper
5.56 NATO:
Military (civilian can own)
About 58,000 PSI which means higher speed and damage
Longer throat
Thicker sidewall and head for higher pressures
Should only be used in 5.56 or 223 Wylde chambers
Usually identified by numbers and a + in a circle symbol and a crimp around the primer pocket
Can be bought when there is a surplus
