5.56×45 vs. .300 Blackout is one of those topics that can spark a massive debate in your gun circle. When you compare an old reliable like the 5.56×45 against a round that hasn’t seen half as much conflict, you’re going to raise someone’s blood pressure. 

You and I will talk about a few points that are often brought up and what I think. If that matters, anyway. 

Anyhow, let’s get into this 1v1 of the 5.56×45 vs. 300 BLK



From left to right: .308 Winchester, 5.56×45, and .300 Blackout. Courtesy of Reddit


Usage In Personal Defense: Which Round Does The Job Better? 

Or more effectively. That’s one of the main debate topics when comparing these two rounds. Which one is more accurate? Which one hits harder? 

Which one is just better all around? 

Unlike modern news channels, I’ll give you some details and let you decide. 

Let’s think of the makeup of the 5.56×45 for a minute. 

5.56×45 is a small rifle caliber with the same diameter as a .22 Long Rifle. It was developed in the 1950s to replace the 7.62×39 due to stability and weight issues. It was designed to be fast and accurate out to 500 yards, and lightweight, allowing personnel to carry more. 

5.56×45 was designed to work out of the M16. Courtesy of Tactical Defense Solution.


Oh, it wasn’t given the 5.56×45 name until it entered service. You know how the military is. 

Anyway, it accomplished all of that. And it’s been in service longer than most of us have been alive. Oddly enough. 

But 5.56×45, being a .22 caliber round, can have problems with stopping power and penetration and the ability to be suppressed effectively. So, the .300 Blackout was born.

.300 Blackout is much larger, much heavier, and works great in smaller barrels (as it was designed to) as small as nine inches. 

You know what that’s great for? Special Operations. Or any unit working in close proximity. And if you want to run a suppressor on your rifle and truly want to be quiet, .300 BLK subsonic rounds are significantly quieter than 5.56×45 when suppressed. 

More importantly, the .300 Blackout has a higher amount of stopping power than the 5.56×45.

With the .300 Blackout, you have a round that can do everything that the 5.56×45 does now but better. 

And it works with AR-15/M4 parts. One of the conditions that needed to be met when the .300 BLK was developed. So you don’t have to go buy new parts outside of a barrel, barrel extension (chamber), and bolt carrier group. That’s pretty much it. 

You save money there… 

But the caveat to .300 BLK is the price per round compared to 5.56×45. Unless you buy crap ammo like Winchester White Box, you’re paying north of one dollar per round. And if you’re a measly gun writer like me, that’s not economical. 

As someone who likes to have enough ammo to arm the eastern seaboard, stockpiling .300 Blackout is not a good idea for someone like me. 

But that may be feasible for you. 

What About On The Civilian Side?

.300 Blackout was made for special operations units and other units that need as much stopping power as possible in order to get the job done. And sometimes has to be quiet. They don’t have to worry about price per round or anything like that.

That’s what ‘taxes’ are for. Or so they say. 

.300 Blackout Upper on ADM Lower. Courtesy of Reddit


On the other hand, we do have to worry about price per round. Yes, I know we talked about that a minute ago, but I firmly believe that .300 Blackout can be the next great combat round IF the price is lower. 

A good training day includes hundreds of fired rounds. And training should be frequent. 

So unless you can afford it, you’re going to be shooting yourself into the red every time you train. Don’t get me started on the price of subsonic rounds. 

That makes 5.56×45 the more economical choice, especially if you train frequently. 

On the other hand, if you can afford to stockpile .300 Blackout, you’re in the green. While I don’t usually recommend a high-power round for home defense due to the penetration capabilities. 

But that’s where the cost per round balances out some. Remember, 5.56×45 sometimes has issues with stopping power on the first shot, especially if the intruder or attacker is under the influence of drugs. 

It may take three, maybe four shots of 5.56×45 to incapacitate the attacker. Whereas with .300 Blackout, the big .30 caliber entering the body will put that attacker down much quicker. 

At the time of writing this, 5.56×45 costs about 60 cents or more per round. Multiply that by three or four, and we get similar costs more. Why shoot four times when you can shoot once? Hopefully, you’re wise enough to have a can on it, though. 

.300 Blackout is loud in close quarters. But definitely effective in short-quarter engagements. 

Long Conclusion

The most important part of comparing two rounds is how well they do their intended job. When you compare .300 Blackout and 5.56×45, it’s clear to see which round does the job better. 

Neither is a long-distance round. They’re both made for close to mid-range engagements and to be used out of a single-man firearm. As we can see, .300 BLK does that job better than 5.56×45 when suppressed and unsuppressed. 

And that’s important. 5.56×45 is still extremely loud when suppressed. Subsonic 5.56×45 is a great way to turn your semi-auto AR-15 into a bolt-action in no time. 

Of course, this is my opinion. In the same way, I clown the 5.7×28 because it couldn’t replace the 9mm when it came out in the early 90s. It had one job. At least .300 Blackout has a purpose, unlike 5.7×28. 

Anyway, you take care and be good.