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.
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.
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.
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.
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.]
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.
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.
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.
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.
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.
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:
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.
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.
.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!]