
In terms of centerfire rifle cartridges, there is a lot of confusion surrounding specific ones. One of our goals with this website is to help clear this confusion up, so we can all be more knowledgeable about ammo.
This time around, we’re going to discuss the 5.56X45mm NATO rifle cartridge in much fuller detail than has been done before. Our goal here, as with anything, is the education of our readers so we can all come away from this with more knowledge.
So then, let’s answer the question —
What is 5.56 NATO?
5.56 NATO is a cartridge designation given to the centerfire rifle cartridge used by most NATO militaries around the world. The cartridge was originally developed off of the .223 Remington, but was ultimately loaded to higher pressures to fit what the military was looking for.
The goal was for the US Military and their allies to have a lighter rifle and, therefore, cartridge, to shoot their enemies with. The result was the AR-15 chambered .223 Remington that would eventually turn into the M16A1 and the 5.56 NATO.
Most of the NATO militaries throughout the world use 5.56 NATO in one way or another, mostly with the M16 and M4 platform select fire rifles.
Are 5.56 and 5.56 NATO the same thing?
The correct answer is yes. 5.56X45mm both with and without the NATO designation are technically the same thing, even if not all of the boxes of ammo labeled as NATO are technically a NATO round. For most of us, including ammunition manufacturers, to be labeled as a 5.56 NATO simply means that the cartridge is loaded to higher pressures than the .223 Remington is.
This is why companies like Hornady label all of their 5.56 ammunition with the NATO designation, even though they use projectiles on some of them that aren’t technically NATO projectiles.
Where some folks differ on this is when they begin to talk about military designation for the projectiles themselves. There are basically different military projectiles, and each one has its own military designation.
Some of these are as follows:
- M855 Green Tip
- M193 Ball
- M196 Tracer
There are plenty of others, but those are the main ones, that are the most popular and well known. And in fact, many ammo manufacturers produce 855 and 193 ammo for the civilian market.
What does 5.56 NATO stand for?
5.56 is the size of the projectile in millimeters, meaning that it is 5.56 mm in diameter. NATO is just the designation given to a round that is accepted for use in the NATO militaries. NATO stands for North Atlantic Treaty Organization and is an alliance of several different countries.
There are several different NATO cartridges, and the 5.56X45 is just one of them. There is also the 9mm NATO, the 7.62X51 NATO, and most recently, the 5.7X28 NATO.
The goal is for the alliance to all use similar stuff, which has the benefit of cross compatibility.
What is 5.56 NATO Green Tip?
The 5.56 NATO Green Tips are rounds with a metal core insert that helps the round more effectively stop a threat. The green tips are often thought about for war, while the 193 ball rounds are typically thought about for range use.
Green tips are generally also heavier than their ball counterparts are, though I’ve found that this is not always the case. The green tipped rounds usually weigh 62 grains, while the others are usually 55 grains. Of course, this just applies to the 855 and the 193 NATO rounds, not 5.56X45 ammo manufactured strictly for civilian use.
For quite a while the uneducated believed these were armor piercing rounds, which they’re not.
The steel core helps the round penetrate further than without, but they ARE NOT armor piercing rounds.
Is 5.56 NATO legal?
Yes, as of the writing of this article the 5.56 NATO cartridge is perfectly legal to own and shoot, at least in the United States. In the past there was an attempt to make M855 green tips illegal because some folks falsely think they’re armor piercing rounds, which they are not.
Can 5.56 NATO kill a bear?
The 5.56X45 NATO can kill a bear but it is not ideal to do so, and I would require something with a bit more power for anything larger than a black bear.
There were reports coming out of Afghanistan where our soldiers were shooting terrorists who needed several shots to be stopped. Last I checked, bear were a lot stronger with more muscle than adult male humans are.
So while it can work, it would certainly not be my first choice.

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Can 5.56 NATO barrel shoot .223?
Yes a 5.56 barrel can shoot the .223 Remington. The projectiles are the same diameter. The main difference between the two as stated above, is that they’re loaded to different pressures, but because the .223 Remington is loaded lower, it is safe to shoot.
Can .223 shoot 5.56 NATO
The problem, as stated above, is that they’re loaded to different pressures, and the .223 Remington chambered rifles are generally thought to be able to safely shoot only the lower-pressure 223 rounds.
While there is a lot of debate about this and some folks disagree, I personally err on the side of caution and only buy 5.56 NATO-chambered rifles, so I can safely shoot both calibers.
Is 5.56 NATO 223?
On one hand, the 5.56 NATO is a 223 in the sense that it utilizes the same size projectiles. Where things tend to differ between the two is the cases are slightly different. The 5.56 is designed to shoot at higher pressures than the 223 Remington is.
5.56 NATO chamber PSI is 58,000
.223 Remington chamber PSI is 55,000
It doesn’t seem like much, but it is enough that it matters and there are documented instances of chambers exploding under the extra pressure.
How powerful is a 5.56 NATO round?
I would personally label the 5.56 NATO as a mid-level rifle round in terms of “power.”
In terms of what the 5.56 NATO replaced, like the 30-06 Springfield, it is not powerful at all. It’s a much smaller projectile, the case holds less gun powder, and the terminal velocity and energy are a lot lower.
That said, the 5.56 NATO is a rifle round and is much more powerful than a handgun. Furthermore, there are some advantages to the 5.56X45mm over the 30-06, like being able to carry more of that ammo with you into the battle field even if it is less powerful.
How effective is the 5.56 NATO?
In terms of effectiveness, the 5.56 NATO saw a lot of hatred from our soldiers overseas fighting the war on terror. There were several reports about how ineffective it was and that the enemy had to be shot several times in order to be stopped.
Those were the main reasons why Remington was approached to make the 6.8 SPC rifle cartridge, which ultimately had its own issues that I’ll cover in a future article.
What is 5.56 NATO used for?
The 5.56X45 NATO is the most popular rifle cartridge that is produced for the most popular rifle in the United States. It can be used to hunt, used for target practice, and used in self-defense whenever a more effective weapon is desired.
Conclusion:
The 5.56X45mm NATO rifle cartridge is often misunderstood, and our goal here was to help shine some light to clear up any confusion. It’s a good round produced for the most popular rifle in the United States, the AR-15, and is a clear staple in the safe of any serious defender.