.300 Blackout Review

What exactly is it?

Ammunition companies are constantly working to improve cartridge technology. New calibers are constantly being developed that seem to push the envelope of what’s possible for range, accuracy and ballistics. It’s incredible to think of how far we’ve come in such a short period of time. Consider this. The first semi-automatic rifle appeared in 1885.

A century later we have high power rifles that are accurate out to 1,000 yards and beyond. In 2017, a Canadian Special Forces sniper in Iraq set the world record for longest range confirmed kill when he shot an ISIS fighter from over two miles away.

One of the newest and most popular rifle cartridges on the market is the .300 Blackout. Advanced Armament in the United States developed this round and brought it to market in 2011.

Since then, the round has grown a large following in the AR community as a great round for short barrel rifles and pistols. So what’s the big deal with .300 Blackout? What can .300 Blackout do that 5.56 can’t? Should your next rifle be chambered in .300 Blackout? Let’s discuss.

5.56 works fine… So what’s the point of .300 Blackout?

.300 Blackout, also referred to as .300 BLK or .300 AAC (Advanced Armament Corp.), was a caliber designed so the M4 style of rifles could fire a larger .30 caliber round similar to the AK-47. The .300 Blackout cartridge looks like a 5.56x45mm casing was necked down to accept a larger, 7.62x39mm AK bullet. That’s essentially what it is. An AK-47 bullet that can be fired in an M4 using the standard bolt and magazine.

Please note: You can NOT fire .300 Blackout in a standard AR-15 chambered in 5.56. This would cause a catastrophic failure. But you can use your rifle’s lower, bolt and magazines if you switch out your upper for one chambered in .300 Blackout.


While the 5.56x45mm round commonly used in the AR pattern rifles has proven effective over the years, there were certain instances where special operations wanted a sub machine gun with a harder hitting bullet. The 5.56x45mm round relies on speed for its terminal ballistics and to get that speed you need a certain barrel length. The 5.56 was designed to be fired from a twenty inch barrel.

This length allows for all the powder to burn off prior to launching the bullet out of the muzzle. Of course, short barrel AR-15s are common and quite popular with military and law enforcement. However, the shorter you go with your barrel length the more your bullet loses speed and effectiveness. An AR-15 pistol with a short barrel will produce a massive fireball as the unburned powder continues cooking off when the bullet exits the barrel.

The .300 Blackout round was designed to burn off its powder in a nine inch barrel, making it ideal for short barrel rifles and rifles running suppressors. The .300 Blackout bullet is bigger and heavier than the 5.56. Approximately twice the size at 125 grains vs 64 grains. This extra size and weight aids in penetration.


The .300 Blackout is based off the .300 Whisper, which was designed for use in a suppressed rifle. It’s available in both subsonic and supersonic rounds. Subsonic rounds fire bullets that travel less than 1,125 feet per second so it doesn’t break the sound barrier.

When a bullet breaks the sound barrier that’s when you hear the loud crack which makes up about half the sound of a gunshot. Don’t get it confused, a subsonic round is not quiet like the movies. But paired with a good suppressor it’s substantially quieter than a supersonic round fired out of an unsuppressed rifle.

The fast burning powder used in the .300 Blackout was designed specifically for short barrels. A .300 Blackout pistol with a nine inch barrel gives you a quiet, hard hitting rifle which is still more compact than a standard M-16. Excellent for close quarters combat and vehicle operations. It’s also handy for the home owner who’s investigating that bump in the night.

.300 Blackout vs 5.56 / .223

The .300 Blackout has a lot going for it. Inside of 300 meters I’d say it’s superior to 5.56. However, there are some major disadvantages to this round. The main ones being the round is less common and more expensive. Expect to pay about twice as much for ammo if you’re running a .300 Blackout. If you train a lot, and you should, then you will feel the pinch in your wallet.

5.56 has about a third of the recoil, making fast and accurate follow up shots much easier. This is especially true for females and shooters of smaller stature. The .300 Blackout is no 12 gauge, but you will notice the slight increase in recoil.

The 5.56 is a flatter shooting round, allowing you to reach out to longer distances with more accuracy. The .300 Blackout uses a heavier bullet which hits hard at close range but starts to drop considerably once you get out past 300 yards.

5.56 ammo weighs about half as much as .300 Blackout. Not a big deal, but it is a consideration if you’re walking around all day with a chest rig full of loaded magazines.

The 5.56 may be safer to use for home defense. Using rifles for home defense is a tricky subject because everyone’s situation is different. Do you live in an apartment building or on a ranch out in the country? This will dictate what you want to use for home defense.

The fact is, 5.56 is less likely to over penetrate inside of a home. Certain 5.56 ammo was designed to fragment and tumble upon impact, which should prevent your rounds from zipping through every wall in your home and continuing on down the street to your neighbor’s house. The heavier .300 Blackout round is similar to the AK-47 round, which is well known for its penetration capabilities.


The .300 Blackout gives shooters the option to have a short, light weight, hard hitting AR pattern rifle that can be reliably suppressed and fire subsonic ammunition. If you want a compact rifle for home defense, this is the perfect option.

I suspect this round will become much more popular in the future. However, 5.56 is just fine for most shooters and is far more economical to shoot. You will have to decide what works best for your applications.


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Written by Sgt. Gunner

Sarge is one olde salty Goat. He is the operator of the popular 1:3 scale miniature gun models. His aim is to miniaturize the 'Greatest of All Time' Guns for users to display on their desks. Get to know the Sarge on a more intimate level by purchasing a miniature gun model at GoatGuns.com