300 Blackout vs 5.56 NATO Ammo

300 Blackout vs 5.56 NATO

Choosing the best ammo for your needs may seem like a daunting task unless you know what you’re looking for. If you have found yourself questioning if perhaps the .300 Blackout or the 5.56 NATO is going to be a good fit, and you just are not quite sure where to start, you have come to the right place. Here, we will be delving into these two different options, both of which you should take the time to check out before making a decision.

To start, let’s look at some of the distinguishing differences between the 300 BLK and the 5.56 NATO. We will then go on to explore how these calibers work for different platforms in order to assist you in making your decision. 

300 Blackout vs 5.56 NATO: What’s the Difference?

Firstly, to understand the differences between these two calibers we must first understand why the .300 blk was invented. Originally designed after the .300 Whisper concept, the .300 AAC Blackout was invented to:

  • Achieve similar terminal performance of the 7.62x39mm round, especially when fired from pistols/short-barreled rifles
  • Maintain similar decibel levels of a subsonic 9mm round when fired from a suppressor 
  • Allow maximum capacity in standard AR magazines, and
  • Accomplish the above all while being fired from the AR platform

Though the 5.56 has many advantages, such as allowing a soldier to carry roughly 3 times as much ammunition as its 7.62 counterpart (a serious consideration in warfare), it lacks in terminal performance when compared to the 7.62x39mm, especially when fired from short-barrel rifles. Additionally, 5.56 subsonic ammunition’s capabilities are limited in night operations and CQB scenarios as the round is still quite loud, hitting anywhere between 135-145 decibels, well above its 9mm subsonic relative.


Given that the 300 BLK offers similar energies as the 7.62x39mm when fired from short-barreled rifles, the round is considered "barrier blind" in that it’s more than capable of penetrating through several inches of various types of hard targets, unlike the 9mm.

As we mentioned earlier, the 300 blk fits into standard AR magazines, such as the stanag, pmag, or AWM. This is because the 300 BLK is basically a larger version of the .223 Remington, the brass case being expanded, reshaped at the mouth, and chopped-down in order to allow for the larger bullet. Though the 300 blk is larger and heavier than the .223 Remington, the overall length is the same at 2.26”. To sum it up, the case dimensions and diameter of the case body are entirely identical, despite the bullets being very different in dimensions and weight.


The best part about the cartridges being virtually identical is that not much is needed to convert a regular AR-15 that’s chambered in 5.56mm to 300 BLK. You just have to change-out the barrel. Furthermore, because the cartridge base is so similar, both the bolt carrier and the bolt remain unchanged.

The Numbers: .300 vs 5.56

One of the biggest differences between the 5.56 NATO and 300 BLK is the weight of the bullets. A standard 5.56 weighs between 55 and 77 grains, while the 300 BLK weighs between 110 and 125 grains. With keeping that in mind, let’s take a look at some of the side-by-side numbers to compare them both a bit more concisely so that you can make a smart choice for your personal wants and needs: 


.300 BLK: 2,220 ft/s (125 gr, 16” barrel)

5.56mm: 2,900 ft/s (62gr, 14.5” barrel)

 Effective Range

.300 BLK: 500 yards

5.56mm: 550 yards

 Common Bullet Weights

300 BLK: 110gr - 220gr

5.56mm: 40gr - 77gr


300 BLK: Fairly Common

5.56mm: Very Common


300 BLK: $0.50 - $3.00 Per Round

5.56mm: $0.25 - $1.50 Per Round

When it comes to choosing between these two calibers, you’re basically looking at a tradeoff. 5.56 Rounds will shoot flatter over extended distances and thereby help you become a more accurate shooter at range, but the 300 BLK is going to provide you with more downrange energy because they are significantly heavier rounds. This, of course, comes at the cost of velocity. Consider these trade offs when making your decision.

To Sum It Up

Both the 300 BLK and the 5.56 have their pros and cons, as is the case with virtually any caliber. Choosing the “right” caliber for you depends completely on how you plan to use your firearm. Do you want ammo that is lighter and faster for greater range or heavier and slower for increased stopping power? Both are more than suitable for the purpose of self-defensive. But, from a hunting standpoint, the 5.56 is typically utilized for hunting varmints, whereas the .300 Blackout is better for coyotes and small game where penetration is crucial. Keep in mind that maintaining and cleaning your gun will help you optimize your performance regardless of which round you choose.

If you have any remaining questions about which caliber to choose, don’t hesitate to reach out to your local firearms store as they’ll more than likely be willing to help. Though the .300 BLK and 5.56 are both cost-effective, you may save yourself some money and hassle when you get some friendly, helpful advice from the place where you’ll likely purchase your firearm. 

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