In 2010, Advanced Armament Corporation developed the .300 AAC Blackout in conjunction with Remington Defense, with the intention of offering a .30 caliber cartridge with better performance than the 5.56mm ammunition currently in use. Replacing the 5.56 NATO cartridge is an idea that has been around since its introduction, but the urgency rose with the global War on Terror, which rapidly placed many of our troops in harm's way across many different situations and unfamiliar geography.

Why Was the 300 Blackout Round Developed?

The key motivator to consider replacing the 5.56 NATO was the increased terminal performance offered by a .30 caliber round. This alone, however, would not necessarily justify wholesale replacement of the military's primary issue rifle. Any cartridge that replaced the 5.56mm would need to be compatible with the M4 weapon system. The .300 AAC Blackout is compatible with the M4 system, since the case was built from the existing 5.56mm cartridge, allowing for the use of the same magazines from the M4, and to full capacity. To convert an M4 rifle to .300 Blackout, the barrel is the only part that needs to be changed.

The noise of the .300 AAC is drastically reduced with the use of subsonic loads and a suppressor. Some describe the resulting noise levels as similar to the Heckler & Koch MP5-SD, which fires 9mm ammunition. Coupled with a bullet about 40-percent heavier than the 9mm fired from the MP5-SD, and moving nearly 100 feet per second faster, the .300 Blackout dramatically outperforms the previous gold standard.

Colt Firearms and other ammunition manufacturers had attempted to chamber AR-type rifles for .30 caliber ammunition – without much success. The problem with the 7.62x39mm, for example, was that it experienced feeding issues unless it used highly specialized and modified AK-47 magazines. The 6.8 SPC and 6.5 Grendel likewise had similar issues.

Unsurprisingly, wildcatters stepped in to come up with a solution. One result was the .300 Whisper, but a wildcatted round is necessarily difficult to adopt for widespread military use. The 300 Whisper round was primarily for single shot handguns. And because it did not have industry standard dimensions, this made it not an ideal choice for use in the AR builds favored by Western military forces.

Development changed when the industry had a bit of an “a-ha!” moment – seeing the M4 or the M16 as the primary recipient of the new, theoretical round. This allowed for greater flexibility of design. The main draw of M4 and M16 builds was that the only mechanical change required for a new round was a barrel change, so no complete conversion of the weapon was necessary.

Development began in 2009, with the lion’s share of the work done in 2010. SAAMI approved the new cartridge on January 17, 2011.

The 300 Blackout Round in the World’s Militaries

Since then, the round has not seen widespread adoption as a standard-issue military round. In fact, it is only in use by special forces in the few places it has been adopted. All told, only three nations have adopted the 300 Blackout:

• The Netherlands: The Netherlands' Defense Material Organization purchased 165 carbines chambered for this round for the Dutch Maritime Special Operations Force in July 2015. This was the first formal purchase of a 300 Blackout-chambered weapon. The suppressed weapon was specially modified and designed to used with ballistic visor helmets.

• United Kingdom: The United Kingdom ordered the round on a five-year contract (with a five-year option to extend) in July of 2017. Not much is known about the order, but the government did note that the round had already been in use previously.

• United States: SOCOM started using the round in March 2017. They quickly began taking proposals from contractors on how to modify the 5.56 to accommodate the 300 Blackout rounds. While the round has seen very limited use in American special forces (mostly within Joint Special Operations Command), the government is looking to broaden its use within SOCOM generally.

300 Blackout vs 5.56 NATO: Which Is Better?

Despite the round being designed for M4 and M16 builds, it has found a captive audience in the United States among aficionados of the AR-15 – America’s favorite rifle. While many AR-15 shooters like the 5.56mm NATO, the cartridge is not without its problems from the perspective of the civilian shooter. Namely, the sound and overall firearm capability.

What’s more, the 5.56mm NATO requires at least a 12” barrel for practicality. However, anything longer than this magic number required to burn off all the powder and avoid a (mostly harmless) fireball means decreased range. There goes your suppressor. The 300 Blackout is thus more powerful as well as more versatile for the average civilian shooter.

Because the 300 Blackout and the 5.56 NATO are so similar, it’s worth taking a moment to compare the two to see which is the superior round for your purposes:

• Market Factors: While prices vary, the 5.56 NATO tends to be significantly cheaper than the 300 Blackout – about half the price. It’s also far more readily available than the newer, less adopted and more niche 300 Blackout.
Recoil: The 300 Blackout has about three times as much recoil as the 5.56 NATO.

• Range: The NATO round wins on range, however, the Blackout is the superior round for hunting game.

• Defense: The NATO round breaks apart on impact, making it a safer and more practical round for home defense than the 300 Blackout. A warning shot fired off with a 300 Blackout round might end up two rooms away, hitting who knows what in the process. It’s specifically designed to break through tough surfaces, making it less than ideal for home defense.

• Hunting: The answer to which round is better for hunting is largely a function of what it is that you’re hunting. Smaller game and mid-sized deer can be hunted with the NATO round within a 100 to 150 yard range. Bigger game with a thicker hide further away is going to require a 300 Blackout to take down.

The max effective range of the .300 Blackout supersonic load is listed at 500 yards, and with the subsonic load, is listed at 220 yards. Muzzle velocity for the supersonic 125 grain FMJ bullet is 2,215 feet per second, and muzzle energy is 1,360 foot pounds. For the subsonic load, muzzle velocity is 1,010 feet per second, and muzzle energy is 498 foot pounds. Downrange, the .300 Blackout is accurate enough to deliver groups smaller than one inch at 100 yards.

The .300 AAC Blackout is a new cartridge with many positives, including its compatibility with the M4 platform. Additionally, it offers increased performance for both supersonic and subsonic applications, which offers clear benefits for military applications. For the civilian market, the cartridge increases the versatility of the AR-15 platform. And due to increased bullet performance, hunters can use the .300 Blackout for harvesting medium-sized game animals.

If those reasons are not enough, the .300 Blackout – with its fantastic accuracy and controllable recoil – enabled SSG Daniel Horner of the U.S. Army's Marksmanship Unit to use the cartridge to win the USPSA Multi-Gun Nationals in 2011. This round offers a great deal to all kinds of shooters, and without a doubt, has a very bright future.

History of 300 Blackout Ammo originally appeared in The Resistance Library at Ammo.com.

Thanks so much for all that information, ADC.

As a (new to the) .300AAC Blackout shooter (I very recently purchased a Springfield Armory Saint Victor), I greatly appreciate being even more fully-informed about a new (to me) round that I plan on having a LOT of range time with.

Pretty sure I’m going to can her up; but, we’ll see...

I’ve been in, out, and back into the 300 Blk game twice now. I wish I had all the ammo back that I let go with the last AR in 300Blk I sold! I’m back in for good now.

I like the round
If your gonna shoot blackout you have to load it.
I load for an AR and a rifle and both need distinctly different loads and brass sizing for real accuracy.
Hopefully in the near future we can stock up on less expensive factory plinking rounds.