Any AR15 lowers can be mated with a 300 Blackout upper receiver. And here are 6 best 300 Blackout upper for AR-15 platforms. The 300 Blackout ballistic performance provides unique capabilities in scenarios that the 5.56 caliber bullet lacks.
While most 9" 300 Blackout uppers are the best options for subsonic ammo, the user can convert their AR-15 into a short-barreled 300 Blackout rifle or pistol
Also be sure to follow your federal and local laws when configuring a 300 blackout upper with barrel length less than 16". Tacticalshooting.com is not responsible for anyone violating the NFA laws.
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Best 300 Blackout Upper Upgrades
Here are some of the best .300 Blackout uppers you can get:
Palmetto State Armory JAKL 8.5"
The 300 Blackout caliber offers a potent combination of power and versatility for the AR-15 platform. It outperforms the 5.56 caliber when used in short-barreled rifles or with subsonic ammunition, making it an excellent choice for those looking to build an unique short barreled rifle based on the AR15 lower receiver. Or build it as a pistol upper.
PSA make a lot of stuff for the AR-15, including .300 Blackout uppers. While most upper receiver groups are fairly standard. This one is a AK / AR hybrid upper receiver with left or right side charging handle, and a proprietary bolt carrier group. It's like a FN SCAR mating with an AR 15 lower.
All you need is the JAKL buffer system or use the PSA JAKL lower build kit to work with a standard AR15 lower, the rear adapter plate is what you really need. You can also purchase the matching upper and lower receivers from PSA.
Two different colors are offered: Black & FDE
Aero Precision M4E1 10"
Aero Precision makes high-quality AR parts. Their .300 Blackout upper comes in 8, 10, and 16 inch barrel lengths.
BCM MCMR 9" 300 Blackout Upper
The BCM® 300 Blackout Upper Receiver Groups offer effortless maneuverability for tactical target shooting. Whether you're navigating tight spaces or engaging targets on the move, this smart design ensures maximum agility, granting you a competitive edge in any tactical scenario.
Besides the regular AR looking parts, the handguard offers 8" of mounting space with MLOK slots in all sides for mounting lights, sling points and modular grips.
The muzzle is the BCM Comp Mod 1 sized for 7.62 caliber bullet for the 300 Blackout. BCM goes the extra mile to ensure utmost precision and accuracy with their 300 Blackout Upper Receiver Groups. By eliminating the sharp handguard cap shoulder, barrel harmonics are significantly improved, resulting in unparalleled shot placement. With this level of accuracy at your disposal, hitting your target consistently becomes second nature.
PSA 16" Pistol Length Gas System 300 Blackout Upper
Palmetto State Armory's 16" barrel 300 blackout upper is the best for the money for anyone wanting a 300 Blackout upper build without having to deal with the NFA laws. The upper features a pistol length gas system, and it doesn't come with a BCG, which further reduce the cost of this upper if you already have some spare parts at home that you can use.
The barrel is made of Chrome Moly vanadium 4150V, with a barrel twist of 1:8 inches. With a nitride coating, it ensures enhanced accuracy and longevity. It's complemented by a .750-inch gas block, a 13.5-inch PSA lightweight rail, and an A2 Flash Hider. Many users have noticed the superior quality and craftsmanship typical of PSA products. One user mentioned shooting super tight groups at 100 yards, showcasing the barrel's precision.
Some even believe that their PSA rifles rival their more expensive Daniel Defense products, offering comparable quality at a fraction of the cost.
Brownells BRN-180
This complete upper receiver is a bit different. It's based on the AR-180 design, which uses a short-stroke piston instead of a buffer tube. This means you can get a folding brace for a really compact AR short barreled rifle.
The 10" nitride barrel, machined from extra-strong 4150 carbon steel, offers exceptional durability and wear resistance. Chambered in 300 Blackout with a 1-8" twist rate, it provides unparalleled flexibility in ammunition selection. The three-prong flash hider replica prevents muzzle blast from kicking up dust when shooting prone.
Longer barrels are available if you don't want to deal with NFA laws.
The BRN-180S now comes with an Adjustable Gas System for the 300 Blackout, allowing you to select between two settings for smooth and consistent operation. Say goodbye to spare gas piston cups and enjoy optimal performance in any condition or with various ammunition.
Daniel Defense 300 S
The Daniel Defense 300 S upper is similar the the famous MK18 upper, but chambered for 300 blackout AAC. The upper comes with the duty grade 9" DDM4 rail system.
The gas system is the heart of any AR-15, and our Enhanced Mil-Spec complete upper receiver incorporates a pinned low profile gas block machined from 4140 hardened steel. With its Mil-Spec heavy phosphate coating, this gas block offers superior durability and corrosion resistance.
Featuring a pistol-length gas system, our gas block ensures optimal cycling and reliable ejection, guaranteeing consistent performance. The direct impingement mechanism provides direct energy transfer, allowing for greater control and precision.
When it comes to barrel performance, The 10.3 inch barrel length is machined from Chrome Moly Vanadium Steel, which undergoes a cold hammer forging process to ensure exceptional strength and longevity. With a 1:8 twist rate, this barrel is optimized for a wide range of bullet weights and provides superior accuracy and stability.
Building A 300 Blackout AR-15
You can change your 5.56 AR-15 into a .300 Blackout AR-15 by just swapping the upper part of the gun. That's all you need to do! You can use the same magazines and other lower receiver parts.
However, be sure to get the muzzle brake or a muzzle device for the 30 caliber bullet. Most 7.62 muzzle brake will work.
Why You Might Want a .300 Blackout
Credit American Hunter
The .300 Blackout rifle cartridge can do some things that the 5.56 can't. It can use bullets that weigh between 110 and 220 grains. The 110-grain bullets are faster than the speed of sound, and the 220 ones are slower. The slower bullets are quieter and easier to suppress.
The .300 Blackout also works best with a 9-inch barrel, while the 5.56 needs a 20 inch barrel length to work best.
Learn more about 300 blackout effective range
It's designed specifically for short-barreled rifles, the 300 Blackout offers enhanced maneuverability in confined spaces, maintains compactness even with a suppressor, and facilitates quicker target acquisition and transition. Moreover, its design ensures efficient propellant burn and pressure release from short barrels, minimizing the blowback of gas, oil, and unburnt powder to the shooter.
Credit Recoil Magazine
The 300 Blackout's versatility is further highlighted by its compatibility with 5.56 magazines, allowing for easy transition by simply purchasing a 300 Blackout upper, attaching it to the AR-15 lower, and loading the magazine with 300 Blackout ammunition.
Best Barrel Length For 300 Blackout
The best barrel length for 300 blackout is 9" for an short barrel AR15 platform when suppressed. Please check out our detailed guide on barrel length for the 300 blackout