What are NATO Rounds?

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The name NATO rounds refers to a set of created standard bullets to allow the armed forces of the countries that make up the NATO force to have standardized ammunition.

The idea behind the standardization was to allow NATO forces the understanding, sharing and ensures the easy fit of ammunition. 

Types of NATO Rounds 

NATO generally standardized only four different types of ammunition across the NATO forces. And those four types are.

  • 9×19 parabellum
  • 5.56x45mm
  • 7.62x51mm
  • .50 BMG

The 9×19 Parabellum

 These are standard 9mm rounds used all over the world in many handguns. Popular handguns include the Beretta 92F, Sig Sauer P226, Glock 17, and 19 among other lots of 9mm chambered pistols. Today, almost every fighting force issues a standard 9mm chambered pistol to their soldiers. The 9×19 parabellum is also used in some Sub Machine Guns that include the versatile and popular H&K MP5.

See our article on 9mm vs 9x19mm for more information on the performance of these rounds

The 5.56×45

 These NATO rounds are also popular in the world especially the US army and the UK armed forces. Most forces within NATO are issued with these special rounds and they are chambered for popular guns such as the M4 or the G36. 

You may want to check out the comparison between 5.56 and 9mm rounds for an exclusive review on their performance.

The 7.62×51

 These rounds are mostly used in rifles and machine guns. They are versatile and have many advantages in power and trajectory. An example of a battle rifle that uses the 7.62 x 45 is the FN SCAR-H.

The .50BMG

 These rounds are extremely popular and NATO forces prefer their use on large fully automatic machine guns. An example includes the Ma Deuce or in the case of British forces the General Purpose Machine Gun (GPMG), also affectionately known as the gimpy. The .50 BMG is also used for big sniper rifles such as the M82, Barrett M107, or the Accuracy International AWM. We have a full review for the 50 BMG which you should check out.

Additionally, NATO forces also use non-standardized rounds for weapons such as the .338 Lapua Magnum, which is a widely used round for snipers across the world.

However, chances are that you have heard the term NATO round or bullet specifically about either the 5.56×45 or the 7.62×51.

Understanding the Difference between 5.56×45 and 7.62×51.

Advantages of 5.56 x 45mm NATO

The advantages of the intermediate power of the 5.56 x 45mmNATO cartridge are summarized as follows:

Penetration and Power 

The 5.56 x 45mm NATO cartridge versions are superior to the 7.62mm NATO. They are also more adequate for the 300-meter average combat range as is documented in actual battle. 

Lower Recoil 

The 5.56mm cartridge generates a lower recoil which allows more control during a full-automatic fire. What this means is that the soldier has greater firepower. Also, recoil is a factor that is dependent on many things and the caliber of ammo is an important condition. Because the 5.56 rifles have practically lesser recoil compared to the 7.62mm NATO rounds, it makes it easier to fire a weapon in full auto mode. Lesser recoil also means improved accuracy for the soldier and a chance of hitting their target with every shot. 

Lesser Weight

A normal infantryman can carry more 5.56 ammo than 7.62 ammo. The 5.56mm ammunition is lightweight which is favorable during combat as soldiers need to carry other equipment as well. 

Smaller Size 

The 5.56mm ammunition is also smaller compared to the 7.62mm NATO ammo. Because of the small size, it makes them favorable for use on lighter, smaller, more compact rifles and squad automatic weapons as well.  


The 5.56mm projectile is greater than the 7.62mm projectile at normal combat ranges. The reason is due to the tendency of the lighter projectile to shatter or tumble on impact. Therefore, the 5.56mm NATO has greater effectiveness and firepower compared to the heavier and larger 7.62mm NATO.  In this, the concept of more for less appears very complicated. 

But this is what it means, lethality is a concept that is aimed to address effectiveness as opposed to killing. The Army had to shift from 7.62 in favor of the 5.56mm because the 5.56mm NATO injures instead of killing. It implies that in a combat situation, it will injure one and as a result, the enemy is forced to withdraw three soldiers out of the combat field to help the injured. It is also more costly for a nation to treat an injured soldier than to pay respect to a fallen Martyr.

Disadvantages of the 5.56mm NATO


A 5.56 round has a lesser range when compared to a 7.62 round. The 7.62mm NATO round can hit up to 800–1000m if you have a decent barrel length. The 5.56mm NATO rounds have a limited range. 

Stopping Power

In the fight against terrorism, most forces prefer using the AK rifles and it makes sense. When fighting Anti Insurgency or running anti-terror ops, you need ammo with high stopping power. In this respect, nothing beats a 7.62mm NATO ammo. A hit by 7.62 means a kill as no one wants an injured terrorist.

Supporting Power

7.62 is the best ammunition for use as a supporting fire by a Machine gun. It is also among the best sniping ammunition due to the power delivery over a longer range that results in great one-shot kills.

In summary, both the 5.56mm and 7.62mm NATO ammunition are good for their roles. In modern combat, the 5.56 is the best ammunition for lighter assault rifles and controllable firepower. The 7.62mm is good for long-range shooting during combat when you need suppressing firepower, and a great first shot kills weapons in a typical anti-terror assault.

Shooting the 5.56x45mm NATO

Are the 5.56x45mm NATO Ammo Interchangeable with .223 Remington

Many people treat the .223 Remington and 5.56x45mm NATO cartridges as interchangeable rounds, it is a dangerous practice and can be quite dangerous under the wrong circumstances.

The two cartridges are indeed quite similar. However, there are some subtle differences between the 5.56x45mm NATO and .223 Remington cartridges. In this article, I will go over some of the differences between the two rounds and some good practices to follow before using any of them.  

Higher Pressure

The biggest difference between the two types of ammo is that the 5.56x45mm ammunition is loaded to a significantly higher pressure compared to .223 Remington ammunition. The higher pressure level of the 5.56 NATO cartridge runs at approximately 58,000 psi and that for the .223 Remington is loaded to approximately 55,000 psi. It means that the 5.56mm chambers are built and designed to withstand increased pressure. Therefore using them interchangeably puts the .223 Remington chambers at a great disadvantage and may not sustain the increased pressure from a 5.56mm ammo. 

Short Leade

Leade is the distance between the mouth of the cartridge and the point where the rifling engages the bullet. The .223 Remington chambers have a shorter leade and a steeper angle compared to that of the 5.56mm chambers. 

Generally speaking, a shorter leade will give increased accuracy but compromise on the pressure hence decreased velocity. Having a longer leade means increased velocity with lower pressures at the expense of reduced accuracy.

 The difference that a 5.56 NATO chamber has a .125-inch longer throat. The extra length allows approximately one more grain of powder to be loaded into a 5.56 NATO cartridge. It is also what gives it a higher performance than the .223 Remington.

The 5.56mm NATO is originally designed as a military cartridge and is supposed to be used with a longer leade and a shallow angle chamber. Besides producing increased velocity, it also has the advantage of improving reliability as it allows more buildup of carbon without adversely affecting the function of the rifle.

Consequences of Firing a 5.56 NATO Ammo in a .223 Chambered Rifle

The biggest problem with the differences is seen when firing a 5.56 NATO cartridge in a rifle chambered for 223 Rem. The longer throat that the NATO chamber uses will cause a .223 chambered weapon to run at approximately 65,000 psi or more. It means that there is an extra 10,000 psi higher than the .223 normally functions at which is a pressure of 55,000 psi. 

It is entirely dangerous and in the chance that the primers back out, or worse, it can cause harm to the rifle, the operator, or both.

The reverse is firing a .223 Rem cartridge in a 5.56 NATO chambered rifle. The throat difference between the two chambers will make a .223 Remington cartridge not to work optimally in a 5.56 NATO chambered weapon. The reason is due to the lack of pressure since the .223 will not attain 55,000 psi and therefore velocity and performance become compromised.  

Problems of a Short Barrel

More problems occur when a .223 Rem cartridge is fired out of a 5.56 NATO chambered rifle that has a 14.5-inches (or shorter) barrel. The lower powder charge coupled with the pressure drop will cause the rifle to cycle improperly. However, NATO chambered rifles with barrels longer than 14.5-inches should function properly when firing .223 ammunition.

Therefore, a shorter leade results in increased pressure than a longer leade. It means firing the 5.56mm ammunition out of a .223 Remington chamber can produce dangerous amounts of pressure.

Not all chambers are the same, and this also applies to ammunition. For this reason, it is possible to fire 5.56mm NATO ammunition out of .223 Remington chambers with no dire consequences. But the combination of ammunition beyond acceptable safety limits with hot temperatures and perhaps some fouling in the chamber means you can run into some serious trouble. Even though the rifle will probably not blow up, it is a possibility. 

The primer can however be blown from the primer pocket on the case and end up somewhere in the internal workings of the rifle. It may lead to a frustrating situation or worse harm to the rifle and the operator. 

To avoid this, always ensure that you fire the appropriate ammunition in your rifle. You must first, find out if your rifle is a 5.56mm NATO or .223 Remington.

How to Determine if Your Ammunition is a .223 Remington or 5.56x45mm NATO? 

If you do not have access to the packaging, look at the headstamp on the base of the bullet. When the headstamp reads 5.56x45mm or is 2-3 letters and 2-3 numbers like “LC 13” and has a cross inside a circle, then that ammo is 5.56mm.

If the headstamp reads differently, like “Hornady 223 Remington,” then it is .223 Remington. In case you are not sure after looking at the headstamp, treat the ammunition as 5.56mm NATO just to be safe.

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You can achieve a safe .223 Remington ammunition shot in either a 5.56mm or .223 Remington chamber. However, you should only shoot 5.56mm ammunition in a rifle with a 5.56mm chamber to avoid suffering a potentially catastrophic incident. 

But if you are looking for a rifle that can shoot the widest varieties of both ammunition, then get one chambered in 5.56x45mm. You should verify that it has a 5.56mm chamber as this will let you shoot both cartridges safely. 

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