300 Blackout: The Ultimate Guide [Ballistics, Comparisons, & More]

300 Blackout Bear Creek Arsenal Suppressed
August 10, 2021 Edited August 14, 2023 55923 view(s)
300 Blackout: The Ultimate Guide [Ballistics, Comparisons, & More]

There is always talk about what caliber will replace the legendary 5.56 NATO, and while we aren’t there just yet -- .300 Blackout has become a standard offering from basically every manufacturer.

What is it? Where did it come from? Is it right for you? We have the answers to that and a lot more!


Where Did .300 Blackout Come From?

Ballistically almost identical to 7.62x39 or .300 Whisper, .300 Blackout was designed for military applications. But has also found a lot of use in civilian shooting.

Developed by Advanced Armament Corporation with help from Remington Defense, .300 AAC Blackout was officially submitted to SAAMI (the trade organization that standardizes cartridge design) as 300 BLK.

The design goals were fairly simple, a .30-caliber cartridge that used standard M4 bolts and magazines while also not losing any magazine capacity.

Able to fire both super- and subsonic ammunition and optimized for use with a suppressor.

Basically -- a cartridge that was quiet, deadly, and modern.

Approved by SAAMI in early 2011, in October of 2011 Daniel Horner won his 4th USPSA Multi-Gun National Championship using a .300 Blackout rifle.

In 2015, 300 BLK was adopted by the Dutch Maritime Special Operations Force. Using integrally suppressed SIG MCX carbines, the Dutch became the first military to publically use 300 BLK.

300 Blackout Military Soldiers

5 years was all it took from development to special forces adoption of this new, interesting, and deadly cartridge.

But the military won’t have all the fun -- since the introduction of 300 BLK, it has taken the civilian shooting world by storm.

With sporting and self-defense applications and with suppressors becoming ever more popular and affordable, 300 BLK has found a niche that no other cartridge can really fill.


Ballistics of .300 Blackout Vs. Common Calibers

Before we get into the best applications, we should put 300 BLK into some context.

There are lots of great chamberings for the AR-15 platform and they all do things a least a little differently, so it’s good to know where they fall in relation to each other.

If you don’t care about the science, you can just skip to the Best Applications for .300 Blackout to get the answers without worrying about the method.


300 BLK Vs. 5.56 NATO

The standard, the one almost all of us start off with in our ARs, the 5.56 NATO. While it has its limitations, it has proven to be a reliable round that gets things done around the world.

Mild to shoot, fairly cheap to feed, and with the right bullet able to do all kinds of different things -- 5.56 NATO is the easiest to compare 300 BLK against.

300 blackout vs 5.56 nato chart

From the chart you can see that to 200 yards, there isn’t a lot of difference in drop between 5.56 NATO and 300 BLK supersonic ammo. But there is a huge difference when using sub-sonic ammo.

Subsonic is really in a category all its own and there isn’t a good comparison to be made with 5.56 since 5.56 subsonic ammo is almost unobtainium unless you load your own.

Supersonic 300 BLK has more power behind it than 5.56 will, although the difference can be marginal.

Really -- the largest difference is barrel length. The muzzle velocity used for 5.56 in the chart is with a 16” barrel, but the 300 BLK is using a 10” barrel.

One of the best things about 300 BLK is that it gets complete burn in a much shorter barrel. Perfect for integral suppressor or just using as an SBR/pistol.

If you want a small package with a big punch, .300 Blackout is a prime choice.


300 BLK Vs. 7.62x39

This chart really makes it clear -- 300 Blk and 7.62x39 are basically kind of the same, ballistically speaking at least.

300 blackout vs 7.62x39 chart

So… why should you consider 300 Blk instead of the more available and much cheaper 7.62x39?

Because 7.62x39 really doesn’t play well in a standard AR-15 package.

There can be a host of issues from magazines to feeding to extraction. But the largest and most visibly distinct difference is the bolt face for 7.62x39 and .300 Blackout.

7.62x39 and 300 blackout BCG size comparison

Because 300 BLK was designed to use the same bolt as 5.56 NATO, it’s stronger. A lot stronger. 7.62x39 requires a much larger bolt face and this makes for a thin-walled bolt that can and will break easier. [We at Bear Creek Arsenal have made modifications to our 7.62x39 bolts and extractors to increase their reliability and durability, however. Watch our video about these improvements here.]

Get it now? While you can build a 7.62x39 AR and get it to run reliably, you will always have an easier time of it and have much better durability with a 300 BLK rifle.


300 BLK Vs. 6.5 Grendel

Really these shouldn’t be in the same conversation since 300 BLK is a short range cartridge and 6.5 Grendel is a long range cartridge, but just in case you were thinking of shooting soda cans at 500 yards with your 300 BLK rifle, take a look at this.

300 Blackout vs 6.5 Grendel trajectory chart

With more than double the drop at 500 yards and falling below the sound barrier before reaching 600 yards, 300 Blk loses the range war.

Remember, .300 Blackout really shines at ranges under 300 yards. You can push it further, but it’s really not ideal.

300 Blackout Rifle Suppressed being fired


Shooting Suppressed

No discussion of .300 Blackout is complete without mentioning suppressors – after all, it’s what the cartridge was designed for. When a bullet is fired, flaming gases released by the burning powder create a bang, which a suppressor muffles by giving the gases room to expand and slow down. But that’s only half of the equation – for truly quiet shooting, you also need to be using sub-sonic ammo.

If you’re unfamiliar with sub-sonic ammunition, the term simply refers to any ammo that travels at less than 1,125 feet per second, which is the speed of sound at sea level. Rounds that travel faster than 1,125 fps are called super-sonic, and when they break the sound barrier they create a sonic boom. Using a suppressor with super-sonic ammunition may mask the position of the shooter, but it won’t reduce the noise of the round breaking that sound barrier.

The answer is to use both a suppressor and sub-sonic ammunition, but that’s where 5.56 NATO starts to suffer. The ballistic performance of 5.56 relies on its high velocity, and without that, the round leaves a lot to be desired. That’s especially true in combat situations, where a lack of kinetic energy and lower penetration could translate into an armed target still being able to shoot back. The problem becomes even more pronounced when the round is fired from a carbine or pistol-length barrel, and that’s where .300 Blackout steps in. Whether you’re using a 7.5-inch, 10.5-inch, or even 16-inch barrel, sub-sonic .300 BLK vastly outperforms 5.56 NATO when fired from a suppressed rifle.

300 Blk is one of those rare cartridges that really excels when it’s moving slowly.If you want the quietest gun possible, you need to run subsonic loads. This reduces your range potential and increases your bullet drop, but it’s really, really quiet.


Best Applications for .300 Backout

If you’re not kicking doors down or quietly sanitizing guard posts, there are still some great reasons for you as a normal person to be interested in 300 Blk.

The two largest are Home Defense and Hunting.


Home Defense

Something that should be a concern to every gun owner is their hearing. On the range and in training we have the luxury of wearing ear protection to muffle the sound of gunshots to a safe level.

But when something goes bump in the night, are you going to have time to dawn your ear pro?

Will your spouse have time? What about the kids down the hall in their room? What about your dog?

In the aftermath of a shooting when you’re being interviewed by police, would you rather have your head ringing from the concussion of firing off a rifle cartridge indoors, or would you like to be able to think clearly while answering questions that your freedom depends on?

One simple tool solves these questions. A suppressor.

300 Blackout Rifle with a Suppressor

While many of us don’t live in a free state -- if you do live in one -- this is a golden age of suppressors.

They are cheaper than ever, more effective than ever, and for now at least more accessible than ever.

Combine that suppressor with a cartridge that is meant to be suppressed and designed to work to the fullest potential with a short barrel and you have a home defense SBR or 300 Blackout pistol that will maximize your safety.

On top of it all, 300 Blackout is tested to be exceptional at NOT overpenetration. This keeps your family and your neighbors safer.



If you need a cartridge with the ability to punch through thicker animal hide, want to hunt quietly (where legal), or just want something different for a change -- 300 Blk is a great option.

Perfect for things like wild boar, .300 Blackout packs a punch and has the mass to get down deep into an animal for an effective kill shot.

With supersonic ammo, you can generally have over 1,000 ft.lbf to at least 100 yards and more than 800 ft.lbf to around 200 yards.

This puts boar, deer, smaller black bear, and other mid-sized game well within your sights.

In every respect, 300 Blk delivers a more ethical round on target than 5.56 can.

If you want to keep it quiet -- subsonic ammo is still powerful enough for smaller game within about 50-100 yards.


Convert My Rifle or Buy A New One?

Buying a new rifle is never a wrong answer if you ask me. But your wallet won’t always agree. Stupid wallets.

Because 300 Blk was designed to work with as many standard parts as possible, it’s actually really easy to get started with it.

If you have an upper laying around you don’t use -- just swap the barrel for a 300 Blackout barrel and you’re done. Since 5.56 NATO and .300 Blackout share bolts/BCG, lowers, handguards, and everything else -- you’re done. Barrel off, barrel on, hit the range. Easy.

If you want it even easier though, you can just grab a new 300 Blackout upper. Switching the uppers are just 2 pins away at all times and make it so that you can always switch back whenever you want.

Just keep in mind NFA laws. If your rifle is a rifle, you’ll need to replace it with a 16”+ 300 BLK barrel/upper. If you’re working off of a pistol or SBR to start with, throw something short on it!


Shop 300 Blackout Uppers


Shop 300 BLK barrels


For Safety Reasons, Keep Your Ammo Separate

Now you might be thinking that a .30-caliber bullet would have no way of chambering in a .223 caliber chamber, but when it comes to 5.56 NATO and .300 Blackout -- you’re wrong.

In my opinion, this is a design flaw with 300 BLK but it’s one we live with. Because of an unfortunate twist of fate, .300 Blackout can sometimes chamber in 5.56 NATO barrels.

Because they use the same bolt face, the same magazines, and the same rifles -- it’s not unheard of for someone to accidentally load 300 Blk into their 5.56 NATO AR.

This is how a .223 round should look in a .223 chamber:

223 Remington Chamber (source Quora)

You would expect this to not chamber and depending on how your chamber is cut it might not. But if the tolerances are just right and the stars aline against you, the ogive of 300 Blackout can chamber against the shoulder of a 5.56 NATO chamber.

300 blackout in a 223 chamber (source Quora)

If you try to fire a 300 Blk round in a 5.56 NATO barrel, you’ll be in for a very bad time.

To avoid this -- be sure to keep your ammo very separate. Personally, I don’t even take both cartridges to the range on the same trip. I don’t want any chance of cross-contamination.

I also have dedicated magazines for both and have my 300 Blk mags marked as such.

As long as you’re aware of what can happen and you take some steps to stay safe, you’ll be good to go.


Final Thoughts

.300 Blackout might have started as being meant for people doing violent deeds in dark places, but it has quickly earned a place in the average gun owner’s safe at home.

From hunting to home defense, this chunky younger brother of 5.56 has a lot of applications and a ton of value to keep around.

Best of all, because of military adoption and widespread civilian use -- it’s pretty easy to find in stores and will be easy to find for a long, long time to come.

It’s not the cheapest, but it is one of the best.

[We would like to extend a huge thank you to David Lane for his work on this article! For more information about AR-15s check out our blog posts on AR-15 vs AR-10 and Side Charging ARs. Comment your next AR-15 build!]


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Alan Rader
August 10, 2021
I enjoyed reading this. Half a dozen deer have been harvested with the stubby cartridge so far and I will be joined by my grandson this year.
Gary Hammock
August 10, 2021
I’ve been looking at the 300 blackout for deer hunting. I really like the AR-15 frame. I first purchased the 5.56, 1-9 twist and realized the heaviest bullet I could use was a 69 gr., and I was pushing that. I shot a doe at about 80 yds in the head. Next year I shot a big buck in the neck at about 75 yds. Both dropped in their tracks. I did have to shoot the buck again. My next AR-15 was a 6.5 Grendel with a 1-8 twist and 20” barrel. I couldn’t find hunting rounds for deer hunting, so I haven’t shot nothing. Plus, I couldn’t find any larger than 123 gr. Now I want the 300 Blackout for deer hunting. After reading this article, I really want one with a 10.5” barrel, because someday I would like to buy a suppressor. Almost all of my hunting deals with 50-200 yds. My question is, should I get the 10.5” or the 16” barrel with side charging. My Grendel is side charging and I really like it. I haven’t read the other to articles you listed at the bottom, but I am after this comment. Thanks a lot for your advice.
August 10, 2021
For hunting I would recommend you get a 16" with supersonic rounds. If you are using a suppressor, a 10.5" with a pistil length gas system, would do. When hunting with a suppressor expect a 3-4 feet drop at 200 yards when using subsonic rounds and little energy from a 16" barrel. There is even less energy with a 10.5" barrel. Just keep in mind that 300 BLK, suppressed, was designed for close quarters. Hope this helps.
Brian Marsh
March 22, 2022
will a 16 inch 300 BLK with a pistol gas system work on my AR15 that has a carbine gas system on the original 556 barrel or does it matter. I notice that the barrels come as carbine or pistol gas systems in the 16 inch length.
March 23, 2022
Yes it will work on a 5.56 upper. Hope you found this helpful.
Brian Marsh
March 24, 2022
I want to understand your reply, I want to put a 16 inch 300 BLK complete upper on an existing 556 lower and does it matter whether the gas system is pistol length or rifle length. I read that the longer gas system has less wear and tear on the rifle as opposed to a pistol length. Should I wait on the availability of the 16 inch with a carbine length gas system or will the pistol length be fine. Are these options conducive to whether subsonic or supersonic rounds are used. I am trying to develop a rifle that can function with various types of ammo for home defense and the possibility that I might have to depend on this arm for survival. I am working on a system of interchangeable firearms that can be transported with minimal storage requirements. Or, just have a lot of fun.
March 29, 2022
There are not very many catch all type of set ups outside of 5.56. In the case of 300 Blackout, you either want it set up to run subsonic ammo without a suppressor or run supersonic ammo without a suppressor that will run subsonic ammo with a suppressor or will only run supersonic ammo. The gas system length has nothing to do with the lower. So, if you are going to want to just put any 300 Blackout ammo you can find in the rifle and shoot it, then I would go with a 16” barrel and a pistol length gas system and then add an adjustable gas block. If you are going to run a suppressor, then I would go with a 16” barrel with a carbine length gas system. There are so many variables out there that based on your individual needs, you may need to do a lot more research on what configurations of firearms are going to be better suited for you. Hope you found this helpful.
Brian Marsh
March 31, 2022
Thanks, this information is very helpful.
Ray Sheriff
November 23, 2022
If you want to use subsonic and supersonic through it the same upper you will need a adjustable gas block to run properly. The two rounds require different gas pressure to cycle. I have a 10.5" and 16" with stranded gas blocks but would chance to adjustable if was using subsonic and supersonic in the same upper. The cost of a upper is $200-$275 so I have both, Hope this helps
Dan R
March 24, 2022
I’ve notice on barrel specs. What’s the proper size gas hole for a 300 BLK on a 16” carbine . I see three different specs (.125, .070 , and .093). I plan to build Stainless steel , black nitride, or parkerize.
Ray Sheriff
November 23, 2022
I have .750 on my barrels.
Lav Elgiad
July 11, 2023
I believe you are referring to the barrel diameter (.750) which determines the size of the gas block. The size of the gas port hole is much, much smaller.
September 7, 2022
Awesome article. I learned a lot and especially appreciate the visuals of the headspace. I will be considering adding this caliber to the stable.
November 27, 2022
Great article! Ty
Rick Brumble
March 19, 2023
A 300 BLK ballistics calculator would be useful here. in 1, 5, 10-yard increments. With so many different loads, an article is not of much use.
May 10, 2023
Have a 300 blackout CMMG 16 inch barrel 1:7 twist, does great with 150gr but when I use 125 or 110 gr it seems greatly off, is the length of the barrel possibly over stabilizing the lighter gr?
Anthony Combs
May 28, 2023
As I see the 30-06 and 270 win. Why not offer both in 1-8 twist as in 270 fast twist now available. This will help ar-10 greatly. Love your products.
June 27, 2023
Great article, very informative. Are there any articles that speak to proper break in for a new upper from BCA?
June 28, 2023
July 11, 2023
Reliably subsonic 7.62x39 is also awfully hard to come by unless you load your own.
Gem Gram
July 11, 2023
With the difference in price so low, it is silly to buy just the barrel from Bear Creek. Don't take that upper apart an add a barrel, just buy a whole new upper ready made and go shooting. You may need that 5.56 AR for another firearm. What is better, one gun and an extra upper, or two guns and an extra upper... for the little bit more you get the second and that IS the correct choice!!!
William O'Neil
July 12, 2023
With so many different rounds for the same platform,that chamber photo is very important...shorter mlock rails leave barrel markings visable... good article.
Richard Wilder
July 12, 2023
Excellent article. Thanks for sharing. BTW I have both uppers in long and short barrels from BCA. Love 'em . . . Please consider a similar article on AR15 Barrel replacement. Thanks . . .
Larry Celine
August 14, 2023
Hello there i just want to let you know how amazing your blog is with such infomative and beautiful captivative contents. I really enjoyed every bit of my time spent on your blog.
Talon Gear
August 16, 2023
This comprehensive guide on 300 Blackout is a treasure trove of information for firearm enthusiasts and professionals alike. The detailed exploration of ballistics, comparisons, and various aspects provides a thorough understanding of this cartridge's capabilities and potential applications. Understanding the nuances of different ammunition types, barrel lengths, and performance metrics is crucial for making informed decisions, whether for personal defense, hunting, or tactical purposes.
Larry Celine
August 24, 2023
Hello there i just want to let you know how amazing your blog is with such infomative and beautiful captivative contents. I really enjoyed every bit of my time spent on your blog.
Reflex Sight
August 28, 2023
Hello there i just want to let you know how amazing your blog is with such infomative and beautiful captivative contents. I really enjoyed every bit of my time spent on your blog.
August 30, 2023
Hello there i just want to let you know how amazing your blog is with such informative and beautiful capitative contents. I really enjoyed every bit of my time spent on your blog.
December 3, 2023
i have the 16in bear creek 300 black out carbine length gas system it wont cycle subsonic. I dont run a can but want to shoot the heavier round.
Larry Celine
December 4, 2023
Hello there i just want to let you know how amazing your blog is with such infomative and beautiful captivative contents. I really enjoyed every bit of my time spent on your blog.
Black Devil Boa
December 5, 2023
Hello there i just want to let you know how amazing your blog is with such infomative and beautiful captivative contents. I really enjoyed every bit of my time spent on your blog.
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