5.56 Vs. 300 Blackout – Which Caliber Do You Need?

Firearm cartridges are a favorite discussion topic among gun owners. Rifle owners are known to give a lot of importance to the cartridges they use. Today, we wish to compare two top-rated cartridges – the 5.56mm and the .300 Blackout. Both these units are used abundantly by militaries across the world, and private rifle owners, too. They have similar origins but different structures and functions. We will try to understand the differences between their ballistics and try to get you closer to choosing between the two cartridges. 

History and Origins

.300 Blackout 

To dive into the historical facets of the .300 Blackout cartridge, we need to travel back in time to the Second World War. In WW2, most military forces were complicit in using the 9mm bullets in their weapons. Rifles used in those battles were capable of delivering shots more than 600 yards away. However, gunmakers and soldiers realized that they needed the power of the rifle bullet for closer warfare. That is because most of the ground warfare happened between distances of 100-300 yards. All the parties involved in the war decided to work towards creating a cartridge that would be as powerful as a rifle bullet but give negligible recoil like a handgun bullet. With that in mind, American gun manufacturers gave birth to the .30 Carbine. 

The western arms market designed the .30 Carbine cartridge to fit the M1, M2, and M3 Carbine rifles. As the popularity of these powerful rifles grew, gunmakers aimed to create a cartridge that would hold 30 rounds in a rifle clip. Here came the advent of the .300 Blackout cartridge. Also known as the .300 BLK, this bullet measures 7.62 x 35 mm in size. The core reason behind the development of the BLK was to create a powerful cartridge that would fit in a short-barreled gun.


A few years after WW2, the US developed the M-16 automatic rifle for its military. They also needed suitable bullet cartridges for the gun. They satisfied these demands by creating the 5.56mm NATO, or 5.56 x 45mm cartridges. These cartridges rectified the problems of stability seen in other 7.62 x 35mm bullets. The 5.56mm bullet did not have the same features as that as of .30 Carbine. Consequently, the military decided to use the 5.56 cartridge in the AR-15 gun. The 5.56mm cartridge is also called the 5.56 NATO because of its widespread use in all NATO forces. 

You should know that each different gun manufacturer has a different make, even for the bullet cartridges. These are minor differences in each make, but no crucial changes in the structure. Now that we are aware of the historical roots of both cartridges, we can move ahead and explore the differences in their design and function. 

Performance And Design 

As we discussed above, both bullets were created because of very specific needs of warfare tactics. They were made for widely different reasons. As a result, both these cartridges have vastly contrasting designs. They also perform differently across various media. We will try to analyze all these differences using a few variables below. For the purpose of this comparison, we will be using a 5.56mm NATO bullet and a .300 BLK manufactured by AAC (Advanced Armament Company).

5.56mm Vs. .300 BLK: Case Comparison 

If you hold a 5.56mm cartridge next to a .300 BLK one, you will find that they look reasonably identical in size and shape. Both bullets have a Remington .223 casing, i.e., they have both been derived from it. They both also have a distinctive bottleneck shape for their containers. If you compare them side by side, you will observe that the neck of the .300 Blackout is a tad bit more prominent than the one on its counterpart. 

Let us weigh in the numbers around both cartridges. Both the 5.56mm and the .300 BLK are 57mm in length. The significant difference is seen in their case length. The case of the 5.56mm measures 44.7mm, whereas the .300 BLK case has a length of 34.7mm. The 10mm difference in case length gives the BLK its prominent neck. Another considerable difference between the two cartridges is that of their diameter. The .300 BLK has a diameter of 7.8mm, whereas the 5.56mm has a 5.7mm diameter.

5.56mm Vs. .300 BLK: Bullet Weight 

Both the 5.56mm and the BLK are available in a wide variety of grain weights. There may be preferred weights for every shooter, but they still are available abundantly. The most common weights for the 5.56mm cartridge are 55 grain, 62 grain, and 63 grain. On the other hand, the most common weights for the .300 Blackout are 78 grain, 110 grain, and 125 grain. 

If you hold both bullets one after the other, you will notice the stark difference in weight that we just mentioned. The BLK is significantly heavier than the 5.56 cartridge. As a result, it is able to travel longer distances with higher momentum.

5.56mm sV. .300 BLK: Power And Range 

Both bullets, the 5.56mm and the .300 BLK, have impeccable power and range. Since both cartridges are used favorably across the globe, they have been tested extensively. Armies and gunmakers around the world have tested all the grain weights of both bullet cartridges. It would help if you thought about the weights of the two cartridges since it is instrumental in carrying the bullet through the air. As we discussed above, the 5.56mm cartridge weights are significantly lower than the .300 BLK. These weight dynamics influence the power generated by the bullet, as well as the velocity with which it leaves the gun. 

In fact, both cartridges were tested using a variety of muzzle lengths. The length of a barrel is also instrumental in determining the power and range of a bullet. Thanks to its low weight, the 5.56mm cartridge is capable of moving at breakneck speeds when the target is at 500 yards. The bullet can travel further while keeping its elevation constant for a longer time. 

Let us take a look at the ballistics of a BLK cartridge and a 5.56mm one after being fired from a handgun. The pistol had a different barrel length for each cartridge – a 9-inch barrel (SAINT Victor model) for the .300 BLK and a 10.3-inch barrel (SAINT Edge model) for the 5.56mm. For the sake of the comparison, we have gathered data of the velocity, muzzle energy, and drop of both bullets after being fired from a Springfield Armory SAINT Pistol. Since both bullets are fired from a pistol, you will observe velocities lower than the maximum potential. 

For a 55 grain 5.56mm bullet fired from the handgun, the muzzle velocity is approximately 2,600 fps. Velocities of bullets are measured in feet per second. For this shot, the muzzle energy is 845.5 ft-lbs. However, as the bullet moves to a distance of 500 yards, its energy drops to a quarter of the original. Let us raise the grain weight by a little bit. For a 5.56mm bullet with a 77 grain, the muzzle energy is higher – 861 ft-lbs. However, the muzzle velocity is slightly lower than the one produced by the 55-grain cartridge. The bullet would leave the gun at a little over 2,200 fps. However, at 500 yards, the bullet would slow down to roughly 300 fps. 

Here come the big guns. A .300 BLK with a 125-grain weight will move at a speed of a little over 2,100 fps. However, the bullet has the capability to generate muzzle energy of a whopping 1,232 ft-lbs. Such high muzzle energy numbers are possible because of the cartridge’s robust weight. The difference between the weight of the two bullets is more substantial than the difference between their muzzle velocities. As a result, the 125 grain BLK ends up producing more stoppage energy than most other cartridges. 

When it comes to shooting a 220 grain .300 BLK from a handgun, the results are starkly different. The bullet ends up producing low energy at a very low velocity. However, the bullet has one redeeming quality. Thanks to its high weight, the bullet retains significant amounts of energy for long distances. The 220-grain bullet produces only 530 ft-lbs of muzzle energy. However, at a distance of 500 yards, the bullet manages to contain approximately 75% of its initial energy. 

The particular difference between the BLK and the 5.56mm is the weight. The standard 5.56 cartridge, being smaller in weight (55-77 grain), can travel flatter over longer distances. At the same time, the heavier .300 BLK bullets, weighing 110-125 grain, carry more energy as they move ahead. BLKs are comparatively bulkier than 5.56mm bullets. Therefore, they lose their elevation as they travel downrange. This phenomenon is called a “drop”. When shooters have targets over large distances, they have to factor in the drop in their shot. The .300 BLK cartridge is expected to have more drop than the 5.56mm one. 

Let us consider the previous example. Using the same guns, let us set up a zero drop at 50 yards for both cartridges. Now, when you fire a 55 grain 5.56mm bullet, it will drop 11.7 inches at 300 yards and more than 70 inches at 500 yards. Now let us consider the heaviest bullet. If we fire a 220 grain BLK shot, it will drop 114 inches at 300 yards and 377 inches at 500 yards. The numbers for the last shot are impossible figures. No shooter can calculate a drop of 114 inches or 377 inches while taking a shot. In fact, the bullet would lose most of its power as it dropped so much elevation. 

Another critical measure of a bullet is its physical momentum. While muzzle energy is the energy that a bullet carries at the beginning of the shot, it becomes difficult to calculate the effect when the shot hits the target. To calculate the impact of your shot, you need to calculate the momentum of the bullet. The momentum will let you analyze how much force the bullet requires to move another object at a certain speed. The momentum of a bullet will be calculated in lbs-fps (pounds-feet per second). Quite obviously, a shooter who is looking for a shot will have more effect. To that end, the .300 BLK will have a more damaging impact than the 5.56mm bullet. The standard 5.56mm bullets may produce 22-28 lbs-fps momentum. At the same time, the most commonly used BLK bullets will make at least 33 lbs-fps momentum.

5.56mm Vs. .300 BLK: Recoil 

The action of firing a bullet from a gun generates tremendous amounts of energy. That energy acts like a punch in the face of the shooter. That specific punch has a name – Recoil. It is an effective blowback for pulling the trigger. As we have mentioned above, the most significant difference between the two rounds is each one’s weight. A standard .300 Blackout bullet can weigh twice as much of a standard 5.56mm round. So, the real question to ask is – how much does the weight affect the recoil? 

The answer – not a lot. The .300 BLK is a stronger, more robust bullet alternative to the 5.56mm cartridge. Therefore, it generates a heavier push when you fire it. While a 5.56mm bullet may be able to generate a 3 lbs recoil, the BLK round will generate 9 lbs recoil in the same circumstances. The funny thing about recoil is that even though a BLK cartridge creates thrice the amount of recoil than a 5.56mm does, you won’t be able to tell the difference. A master shooter is trained to take any shot despite recoil. The difference between the two recoils is imperceptible, and therefore, recoil does not differentiate the two bullets.

Cost Of Use 

The 5.56mm cartridge is one of the most widely used ones in the world. Comparatively, the .300 BLK is used less. Therefore, the prices of each round are also determined by their demand. A single round of 5.56mm bullets can cost under USD 1. However, at the same time, a single .300 BLK bullet will cost closer to USD 3. Due to constantly shifting economics, the prices of these commodities are not fixed. Also, the price of BLKs was expected to drop by approximately 0.5 USD in 2020.


Looking at the costs of the cartridges, we are all wondering how abundantly they are available in markets. For starters, purchasing ammunition is no child’s play. In most parts of the world, buying guns and ammo is an arduous task. It is an unsaid truth that the arms industry operates on illegal levels in most parts of the globe. In the places where you can quickly get your hands on guns and ammo, dealers are cutting down on supply. Most notably, the trend in ammo manufacturers has been to choke the supply lines of the 5.56mm cartridge. Since it is widely used all over the planet, a supply cut will only raise prices. Therefore, the most commonly used rounds have become the most uncommon in today’s markets.

Usage In Society 

Both the 5.56mm and the .300 BLK have widespread applications in modern society. However, the most prominent one has to be the usage of these cartridges in law enforcement and the military. A close second has to be the use of these rounds in professional shooting competitions. Thirdly, a significant portion of gun-owning citizens prefer to own these rounds because they have a credible and trustworthy image. 

The 5.56mm and the .300 Blackout are both used in very similar guns. They both make up a substantial chunk of automatic rifle magazines. Even in the area of automatic rifle ammo, the 5.56mm bullets are the biggest sellers. However, the .300 BLK is starting to get in on the action. In fact, the BLK is also beginning to find its niche in becoming the prime choice of private gun owners. They are starting to feel that the BLK round is the ideal choice for self-defense needs. The impressive ballistics of the BLK has also impressed the hunting community. 

Gun experts say that if you are trying to get into shooting, the best way to build a gun is to go for one that can support both kinds of cartridges. That way, you can use the 5.56mm for target practice and the .300 BLK for self-defense needs. 

Terminal Ballistics 

Terminal Ballistics is an arena where the differences between these two bullet cartridges can shine. So, what does terminal ballistics mean? It is the analysis of the bullet and cartridge after it has hit the target. Penetration, density, and fragmentation are the main areas of study when it comes to terminal ballistics. It is a complex study of the behavior of the bullet that enables us to understand the true potential of every firearm and its ammunition. 

The impact and drop of a bullet cartridge come into question when we study terminal ballistics. For example, terminal ballistics will help us determine the effect of a 5.56mm bullet that caused damage because of its velocity in spite of its small diameter. That way, a 5.56mm cartridge can cause sheer damage powered by its speed through the air. The bullet might even surpass the areas where it lacked. 

On the other hand, a .300 Blackout is also a phenomenal bullet that can cause substantial damage because of its weight and large diameter. In that case, we can study the bulky body of the BLK to determine its fragmentation. This way, we can conclude how effective the shot itself was. 

What Is Supersonic And Subsonic Ammo? 

You can segregate ammo into two major types – supersonic and subsonic. The distinction here is fairly literal. Supersonic ammunition includes those bullets that can break the sound barrier, i.e., they can travel faster than sound. Subsonic ammo has all bullets that travel slower than the speed of sound. Sound travels at 340 mps or 1,125 fps. A tiny hint for all you readers – whenever something breaks the sound barrier, it makes a loud “crack” noise. 

When gunmakers developed the .300 BLK, they intended for it to be suppressed ammunition. As a result, the BLK has multiple subsonic options from which you can choose your ideal make. The physics is really straightforward with this one – the higher the grain of your ammo, the more likely it is to be subsonic. 

What Is The Best Round – The 5.56mm Or The .300 Blk? 

If you are a part of the military or law enforcement and you want bullets that will ensure bad-guy-kills, there is no better option than the .300 Blackout. The BLK is designed for combat and warfare. The cartridge is also used widely everywhere and can fill the magazine of many rifles. 

On the other hand, the 5.56mm is arguably the more popular and civil choice when it comes to purchasing ammo. The cartridge has found its place in a handful of rifles used by a considerable number of people. Between the two, the 5.56mm cartridge is more affordable, making it the obvious choice for any buyer. 

If you are purchasing ammunition for self-defense, either bullet can be a good choice. However, if you would rather have a silent suppressed weapon, the .300 BLK is a brilliant choice. 


We discussed the two most popular and well-known cartridges for automatic rifles in this article. We tried to discuss their origins, their intricacies, and the differences in their structure and function. The article was aimed at covering all aspects of the bullet so that you would be able to make an informed decision. It is still a close battle between these two cartridges, but the choice is yours. Remember, use your firearm safely.

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