Of all the AR-15 calibers that have been developed over the last few decades (6.8 SPC, 6.5 Grendel, .224 Valkyrie to name a few) .300 AAC Blackout is probably the one that has seen the most success.
If you’re thinking about a .300 BLK build of your very own, or just want to see what all the fuss is about, you’ve come to the right place.
Today, we’re going to take a look at what makes this round so special, as well as some of the best guns chambered for it. Then, we’re going to look at some of the best .300 BLK uppers to give you an easy way to convert your AR-15 to shoot .300 Blackout.
Let’s get started.
What Is .300 Blackout?
Back in 2009, Advanced Armament Corporation set out to develop a round that was ballistically similar to the 7.62x39mm, in a form factor that could be fired from a standard M4/AR-15 platform rifle without losing any capacity in standard 30 round mags.
They had military customers that wanted a harder-hitting round for short-range, suppressed usage, and over the course of a year, and in combination with Remington’s defense arm, they developed the .300 AAC Blackout.
It is based heavily on the .300 Whisper and other similar wildcat cartridges and can be seen as a more standardized version of some of these rounds. AAC wisely took these existing cartridges and polished them a little bit and submitted those specs to SAAMI to create the .300 AAC Blackout we have today.
The round uses the same case head diameter and length as the 5.56/.223 you’re probably already familiar with, which makes it easy to swap to if you already have a 5.56/.223 AR. All you really need is a new barrel, and swapping an upper can have you shooting the new caliber in mere seconds.
.300 BLK vs 5.56
One of the most common questions we get about this caliber is “So what exactly is the difference between .300 Blackout and regular ol’ 5.56x45mm?”
First and foremost, .300 Blackout shoots a bigger, heavier bullet. This matters an awful lot in terms of the amount of energy delivered to a target downrange. While this originally came about because of the military applications of a bigger, harder-hitting bullet, it has helped the round catch on with hunters in the civilian world as well.
It’s particularly popular in densely-forested Southern states where hunting whitetail and feral hogs are popular pastimes, and shots at less than 200 yards are definitely the norm. .300 BLK excels at these distances and delivers a considerably larger bullet than the 5.56. Some subsonic .300 BLK loads spit a 220gr projectile, which is a big jump from your “‘heavy” 5.56 pills which sit at 77gr.
The .300 BLK also suppresses really well. We know that big, slow rounds are easier to suppress, and subsonic .300 BLK is no exception. The cartridge it’s based on carries the moniker “Whisper” for a reason, after all. It has a much quieter sound signature out of similar suppressors than the higher-velocity 5.56.
It also is notably better in shorter barrels, making it a favorite among SBR owners. The .300 BLK can burn all its powder and hit the point of diminishing returns in velocity gains out of just a 9” barrel. The venerable 5.56 needs a barrel with a length of at least 16” to get its full run-up to max velocity and total powder burn. \
The tradeoff, of course, is that you have much more bullet drop downrange. The heavier, slower .300 BLK rounds drop further than similar 5.56 at all ranges, but especially once you start getting past 200 yards.
So what’s that all mean? The .300 BLK excellent for close-range shots where penetration is the name of the game, and the 5.56 remains the choice for shots at more medium range.
Why Shoot .300 BLK?
So, with all that in mind, why would you shoot .300 BLK over 5.56?
Ballistically, .300 BLK is fairly similar to the 7.62x39mm cartridge, but it has been designed to cycle much more reliably in the AR-15 platform thanks to some changes to the case geometry, and length.
All .300 BLK rounds should feed reliably from NATO STANAG standard magazines, making this a good option for many Western militaries, and for any civilians that already have a bunch of mags lying around who want a harder-hitting bullet they can launch out of their existing AR.
It’s especially attractive to those who are willing to fill out some forms and get their SBR and suppressor tax stamps as it performs admirably in short-barreled rifles, and suppresses like a dream. This makes it an excellent choice for AR-15 pistols as well, and is the reason you see so many of those chambered in .300 BLK.
You also don’t get the huge fireball with an unsuppressed .300 BLK out of a short barrel like you do with a 5.56 either, thanks to the Blackout’s ability to burn the vast majority of its powder with just 9” of barrel. This is either a pro or a con depending on your perspective, but generally, we like being able to actually see our target the whole time we’re shooting.
Finally, you get much better performance in terms of velocity and energy than you do with 9mm and .45 cartridges as well, which makes .300 BLK a great option for someone who is considering a pistol-caliber carbine, especially someone who is looking to run a can as well.
Best .300 BLK Guns
With all that having been said, let’s take a look at some of the best .300 BLK guns (and uppers) on the market right now. These are the guns to go with if you’re looking to shoot .300 BLK and want a rifle that’s ready to go out of the box.
1. Daniel Defense DDM4V7P 300 Blackout
First up we have the Daniel Defense DDM4V7P in .300 Blackout. This less-than-poetically-named AR pistol is designed primarily for law enforcement, but that doesn’t mean that it doesn’t work well in civilian hands too.
This pistol features a 10.3” barrel, an SB Tactical SOB stabilizing brace, and a Law Tactical folding stock adapter, making it a great choice for a truck or backpack gun as it takes up very little space, particularly with the stock folded up.
It also features a suppressor-ready gas system that is specifically designed to redirect gas up and away from the operator’s delicate face and eyes. If you’ve ever been behind an over-gassed rifle running a suppressor, you know how rough it can be getting those gases in the face with every shot…not a problem you’ll have with the DDM4V7P.
Even if it does have a name only a marketing exec could love.
2. Barrett REC7 DI
Next up we have the Barrett REC7 DI, the new and improved version of the incredibly popular REC7 line, this time featuring Barrett’s Enhanced M-LOK handguard, Magpul furniture, and classic FDE Cerakote.
It also features an accuracy-focused ALG QMS trigger, as well as a specially designed gas block from Barrett to help the gun run well when suppressed. The 16” barrel is great for hunters as it’ll give you that little bit of extra velocity, but of course, it’s also just a good option if you’re not interested in an SBR or in doing the AR pistol thing.
3. Wilson Combat Ranger
Wilson Combat may be mostly known for their 1911s, but don’t let that reputation fool you. They make excellent ARs as well.
One great example is the Wilson Combat Ranger, which is a truly beautiful sight to behold. And beautiful to actually hold as well.
It combines Wilson Combat’s excellent billet upper and lower receivers with their proprietary Ranger profile match-grade barrel. The barrel is the main attraction here as it has been designed by Wilson to shave off as much weight as possible, while still retaining the mass needed to work well for rapid-fire strings without heating up too much.
In tests, this barrel did much better than most other lightweight AR barrels, making this rifle an excellent option for anyone who wants a light, maneuverable rifle in .300 BLK.
4. Ruger American Ranch Bolt Rifle Action
Speaking of lightweight, maneuverable rifles, we have the Ruger American Ranch Rifle. The Ranch Rifle series is a favorite amongst plinkers, varmint hunters, and traditional rifle fans.
This bolt-action gun weighs under 6lbs, and takes AR-15 magazines, making reloading a breeze. This is a great option for hunters, particularly those who want to run a suppressor as it has a threaded barrel. The American Rifle series from Ruger is incredibly popular thanks to its smooth action and excellent performance at range, and that’s evident here as well.
5. IWI Tavor X95
Finally, we have the bullpup IWI Tavor X95. This rifle shares the same bullpup design as the popular Tavor-7 and TAR-21 rifles from IWI.
This new version has a much better trigger (for a bullpup), a better-positioned mag release, and some tweaking of the charging handle position to make it much smoother to use. All these changes come coupled with the classed tri-rail front end and railed top to give you all the room you need to mount all your favorite optics, lights, and lasers.
You also get the somewhat controversial TAR-style pistol grip, but if it’s not to your preference you can swap it out for a more traditional grip and trigger guard without much effort at all, making this one of the easiest bullpups to get used to if you’re used to more traditional ARs.
Best .300 BLK Uppers
Next up, we have .300 BLK uppers. Picking up an upper is a great way to get more out of your existing rifle, and is of course much cheaper than picking up a whole new gun.
And best of all, since the serialized part on an AR-15 is the lower, you can have your upper shipped straight to your house, no transfer or FLL required!
1. Aero Precision M4E1
First up, we have Aero Precision’s ever-popular M4E1 series of uppers. These Enhanced uppers are some of our most-often recommended options for 5.56 guns, and the .300 BLK versions are just as good.
Like most things from Aero, the machining is impeccable, and you have a variety of colors to choose from, especially when you look at their limited edition builder’s kits.
The 7075-T6 aluminum of the upper is as robust as you could want, and the enhanced handguard features scalloped rails, machined QD sockets, and enough room inside for low-pro gas blocks and 1.5” suppressors as well.
2. Palmetto State Armory 10.5” Complete Upper Receiver Kit
PSA is known for their awesome, budget-minded rifles and parts, and this 10.5” .300 BLK upper kit is yet another excellent offering aimed at meeting the needs of the more budget-conscious consumer.
Don’t be fooled into thinking that “affordable” and “cheap” are the same here, however. These uppers are rock solid and reliable. PSA has just nailed their manufacturing processes and are really good at what they do.
And what they do is provide awesome guns and gear at awesome prices, so if you’re looking at building a .300 BLK AR pistol without spending a whole lot of money, this is the route to go.
3. Radical Firearms 8.5″ .300 BLK Upper Assembly
Speaking of affordable upper options, if you’re looking for a shorter barrel on your .300 BLK AR pistol or SBR, then this shortie from Radical Firearms might be just what you’re looking for.
These uppers are specifically tested to make sure they cycle well with subsonic ammo, making this a good option for a suppressor host as well. You also get Radical’s free-float quad-rail handguard, which of course gives you all the room you need to mount…well, whatever it is you need.
Finally, this is a complete upper, so it’s ready to go out of the box. The only other things you need are your standard BCG and charging handle and you’re ready to go.
4. Radian Weapons Model 1
Last, but certainly not least, is the Radian Weapons Model 1 upper. This upper receiver is hand-assembled and test-fired by licensed gunsmiths at Radian to ensure reliable performance with or without a suppressor, and with subsonic or supersonic ammo.
Radian also has a sub-MOA accuracy guarantee on this upper when used with Black Hills Match Grade factory ammo, so if you’re looking for something that’s going to be extremely accurate at close ranges, this is the route to go.
Overall, this is a great premium option if you’re really committed to the .300 BLK cartridge and want to get the absolute most performance out of it that you can.
That’s about it for this one. Hopefully, you learned more about the .300 BLK and some of the great guns and AR-15 uppers that are chambered for it.
The .300 AAC Blackout is a great cartridge, but to really let it live up to its capabilities, it needs to be coming out of a great gun. With these completed rifles and uppers, you can rest assured that you’re getting something worth buying, and you’ll be able to get the most out of this awesome round.
Did this list help you find what you’re looking for? Which .300 BLK rifle or upper do you think you’ll be going with? Is there another that you think we should have included in this list? Let us know in the comments below. Don’t forget to check out the Best .300 Blackout Ammo, too!