When you think of rifles that offer solid ballistic energy at close ranges while performing superbly when suppressed, the AR-15 is often one of the first platforms that comes to mind. However, its primary caliber, 5.56, doesn’t necessarily fit that role.
Enter .300 Blackout. This cartridge is one of the most popular ones around for the AR-15, second only to 5.56. It offers excellent ballistics with an effective range of around 400 to 480 yards, and can even be hearing safe when shooting suppressed, depending on your suppressor and ammunition.
Moreover, it’s an approachable alternative caliber to 5.56. If you’re new to the AR-15, you might be confused. Below, we explain what makes .300 Blackout such an awesome cartridge.
What is .300 Blackout?
.300 Blackout is an alternative caliber chambering for the AR-15 that uses a .30 caliber projectile instead of a .22 caliber one like 5.56. 5.56 offers higher velocities and a flat trajectory, making it a good all-around cartridge for shooting at close to medium ranges. However, due to its reliance on velocity, 5.56 doesn’t perform well out of shorter barrels and is often loud, even when suppressed.
In contrast, you have .300 Blackout, which was introduced in 2011 by AAC and was specifically designed to be more easily suppressed while delivering better stopping power at close ranges. It’s become an incredibly popular caliber for SBRs and AR-15 Pistols, and it’s also seen success as a home-defense caliber. It’s since been adopted by various Law Enforcement groups and Militaries for its effectiveness in CQB applications.
Making the switch to this .300 Blackout is relatively simple too. We’ll go more in-depth on it shortly, but realistically, it’s possible to switch from 5.56 to .300 Blackout is as simple as changing out the barrel. While it’s easier, and more practical, to have a separate upper receiver, 5.56 and .300 Blackout components are largely the same, though you may need to switch out your buffer weight for optimal performance.
.300 Blackout vs. 5.56x45mm/.223
Like we mentioned before, 5.56 and .300 Blackout are absolute powerhouses that excel extremely in their given roles. That said, how do they stack up against each other?
Ballistic Performance
A key difference between these two cartridges is their ballistic performance. Depending on the type of cartridge, 5.56 projectiles can excel well beyond 3,000 FPS, making it capable of landing accurate shots on targets upwards of 500+ yards away, and can be effective much further depending on the cartridge. .300 Blackout runs at much lower velocities, usually around 2,000 FPS, and its larger projectile causes it to slow down and drop in trajectory much quicker. That said, at close ranges, .300 Blackout packs a serious punch, especially when compared to PCCs or similar ultra-short carbines. When you’re comparing barrels under 10 inches, .300 Blackout will easily outperform 5.56, which requires longer barrel lengths to reach its effective velocity.
However, since 5.56 uses a much smaller, lighter projectile that’s moving extremely fast, it offers a much flatter projectile flight path. .300 Blackout instead has a more parabolic flight path. To put it into perspective, a 62 grain FMJ 5.56 will drop by around 17 to 18 inches at roughly 400 yards, while a 150 grain FMJ .300 Blackout drops roughly 72 inches at the same distance.
Suppressor Effectiveness
Although any caliber’s sound signature can be suppressed, some can do so more effectively than others. .300 Blackout was designed for use with suppressors, so by default, it offers one of the best suppressed shooting experiences, being capable of effectively cycling different ammo types without much alteration to the rifle. That includes subsonic ammo, as many .300 BLK rifles will have an adjustable gas system to shoot subsonic ammo reliably.
This makes .300 Blackout one of the most ideal cartridges for dedicated suppressor use. If you’re looking at getting one for use with a suppressor, our guide on how to buy one provides a lot of useful info on the buying process.
.300 Blackout vs. 7.62x39mm
.300 Blackout is commonly compared to 5.56 since they’re both primarily used on the AR-15, but there’s another caliber that more closely compares with it, that being 7.62×39. If you’re unfamiliar with the cartridge, 7.62×39 is a caliber that’s well-known for being the caliber used in the AK-47/AKM platform.
.300 Blackout and 7.62×39 Similarities
Although it’s primarily used on AKs, it’s been adopted on many AR platforms. Compared to other AR-15 calibers, it’s a more robust cartridge, offering solid ballistic performance with an effective range of roughly 300 to 400 yards. Compared to .300 Blackout, both cartridges offer similar ballistic performance at close ranges, making them ideal for shorter carbines or SBRs, and they both can be suppressed rather effectively. They’re also remarkably similar in size, in fact, .300 Blackout’s metric measurement is 7.62×35, meaning there’s only a 4-milimeter difference in the casing length for both cartridges.
.300 Blackout and 7.62×39 Differences
There’s often an ongoing debate in the community regarding .300 Blackout vs. 7.62×39; while similar, they have their differences. To start, 7.62×39 was designed to be used as an intermediate rifle cartridge before suppressor use was as widespread as it is today. By happenstance, it can be suppressed easily when using subsonic ammunition, but since that wasn’t it’s intended purpose, it isn’t as easy to suppress compared to .300 Blackout. Also, 7.62×39 doesn’t have the same ammunition variety as .300 Blackout. Though, there is still a fair assortment of ammo variety for 7.62×39, it just isn’t on par with .300 Blackout.
If you plan to build out an AR-15 with one of these calibers, .300 Blackout is the easiest cartridge to switch over too. Most .300 Blackout ammo can be loaded into a 5.56 magazine without any issues, though there are also dedicated .300 Blackout magazines, which are designed for greater reliability with subsonic ammo. Both cartridges share the same bolt face too, so any standard mil-spec BCG will work as well, making the .300 Blackout one of the most approachable caliber swaps available for the platform.
7.62×39 requires you to make some concessions. To start, 7.62×39 requires specific magazines to be used with mil-spec AR-15 lowers and you’ll also need a different BCG, as it uses a different bolt face. It’s worth mentioning that there are specialized lower receivers that allow your AR to take AK magazines, but they’re counterintuitive if you’re trying to keep the core functionality of the AR-15. Still, they’re worth looking into if you’re wanting to build a sort of AR and AK hybrid.
Best .300 Blackout Rifles and Accessories
Rifles and Uppers
Building a .300 Blackout AR-15 offers many benefits, and many quality rifles and uppers are available. For instance, Daniel Defense’s DDM4 is one of the most popular AR-15s one the market, and it’s available in .300 Blackout. It’s currently available as a rifle or pistol/SBR with 16- and 10.3-inch barrels, respectively. They also produce an ultra-compact PDW style AR, the DDM4PDW which features a 7-inch barrel and is available in either a pistol or SBR configuration. Depending on which you choose, it comes with either a Maxim Defense CQB Pistol Brace or Stock. Since it uses a PDW style stock or brace, it can collapse down to an overall length of 20 ¾ inches.
If you aren’t interested in buying a new rifle, there are dozens of .300 Blackout upper receivers available from premium manufacturers. Options like the Noveske Rifleworks Gen 4 N4 Shorty features a 10.5-inch stainless steel barrel and comes standard with their Pig Pen muzzle device. If this one doesn’t quite scratch the itch for you, there are dozens upon dozens of options for you to choose from, including some from popular brands like Knight’s Armament Company, Aero Precision, and Daniel Defense too.
Accessories
If you’re shooting suppressed, one of the main problems enthusiasts face comes in the form of gas blowback. Suppressors increase your rifle’s back pressure, causing excess gas to dump out through the chamber and gaps in the charging handle guides. One way to mitigate this problem is by using a gas-busting/suppressor charging handle. We featured them in our charging handle guide, however, to sum them up, they include strategically placed cuts to help prevent the gas from inadvertently coming back to your face. While not 100% necessary to be able to shoot, they make for a more pleasant shooting experience.
Optics
In terms of optics, most reflex sights will get the job done, however, there are select optics, such as prism scopes, which feature reticle systems calibrated specifically for .300 Blackout.
Our SLx® 3x MicroPrism Scope features the ACSS Raptor 7.62/300 Reticle, which, as one might guess, is a BDC calibrated for use with .300 Blackout. This reticle has holds for wind and range, maximizing the utility of your rifle.
Conclusion
.300 Blackout has cemented its legacy as one of the most popular calibers for the AR-15 and AR alternatives. From its short-barreled performance to its ability to be easily suppressed to near hearing-safe levels, it’s a great caliber worth considering for your next rifle build.
Whether you’re wanting to use it for home defense, competitions, or simply to add some variety to your collection, the .300 Blackout provides a superb balance of power, flexibility, and suppressed shooting capabilities.
If using a suppressor is unfamiliar territory for you, we recommend checking out our guide on how to shoot with one, it’ll get you familiar with the basics of owning a suppressor as well as some techniques for optimal use.
