.300 Blackout Cartridge Overview
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The .300 AAC Blackout, also known as 7.62x35mm, is an intermediate rifle cartridge developed in the United States by Advanced Armament Corporation for use in the M4 carbine, offering increased performance and versatility compared to the 5.56mm NATO round.

Origins of .300 Blackout

The .300 AAC Blackout (300 BLK) cartridge was developed in 2009-2010 by Advanced Armament Corporation (AAC) in cooperation with Remington Defense to meet a military requirement for a .30 caliber cartridge that could be fired from the M4 carbine platform using standard bolts and magazines while retaining 30-round capacity. It was intended to address shortcomings of other .30 caliber cartridges like 7.62x39mm, 6.8 SPC, and 6.5 Grendel when used in AR-15 style rifles. Previous attempts by manufacturers like Colt to chamber AR-pattern rifles in .30 caliber rounds faced issues like feeding problems requiring modified magazines (7.62x39mm) or reduced magazine capacity (6.8 SPC, 6.5 Grendel). Wildcat cartridges like .300 Whisper solved some issues but lacked standardized dimensions and had powder charges incompatible with M4 pressures, causing reliability problems especially with subsonic ammo and suppressors. AAC's solution was to develop the .300 BLK based on the .300 Whisper concept but optimized for the M4 system. It uses the .223 Remington parent case allowing use of standard AR-15 magazines and bolts with only a barrel change required. SAAMI approved the cartridge on January 17, 2011. The .300 BLK provided enhanced ballistics over 5.56 NATO from the same platform, with better terminal performance yet subsonic capabilities when suppressed - filling an operational need for some military units. In 2011, the cartridge gained fame when used by a U.S. Army shooter to win the USPSA Multi-Gun Nationals before rules changed.

Military Adoption of .300 Blackout

Here is a concise overview of the military adoption and use of the .300 AAC Blackout cartridge:
  • Netherlands
    • In 2015, issued tender for 195 .300 BLK carbines for Dutch Maritime Special Operations Force (NL-MARSOF)
    • In 2016, NL-MARSOF acquired 195 suppressed SIG MCX carbines in .300 BLK, becoming first publicly known military user
  • United Kingdom
    • In 2017, issued 5+5 year contract for .300 BLK supersonic and subsonic ammunition, noting it was already in use
  • United States
    • In 2022, U.S. Special Operations selected SIG's MCX Rattler PDW in 5.56 NATO and .300 BLK for its compact 5.5" barrel in .300 BLK
  • Germany
    • In 2024-2026, procuring 1,700 H&K 437 rifles in .300 BLK for Schleswig-Holstein state police SWAT units
    • In 2024, ordered ~1,000 suppressed H&K 437 "G39" rifles in .300 BLK for Bundeswehr Special Forces KSK unit
The .300 Blackout has seen increasing adoption by various military and law enforcement special operations units, particularly for its sound suppression capabilities in a compact AR-15 platform when using subsonic ammunition. Its design allows use of standard magazines and components.

Versatile Cartridge Advantages

One of the key advantages of the .300 Blackout is its exceptional versatility. It can fire both supersonic and subsonic ammunition from the same rifle simply by changing magazines. This allows it to serve a wide variety of roles - from hunting medium game with supersonic loads, to home defense with suppressed subsonic ammo for reduced noise and flash. Its ability to quickly switch between super and subsonic gives it an edge in dynamic situations. Another major benefit is compatibility with the AR-15 platform. The .300 Blackout was designed to function reliably with standard AR-15 magazines and bolts, requiring only a barrel change to convert. This makes it an easy upgrade for existing AR owners and simplifies logistics. The .300 Blackout particularly excels in short-barreled rifles (SBRs) and carbines. Its case design allows for efficient powder burn and maintains good ballistic performance even from barrels as short as 9 inches. This gives it an advantage over calibers like 5.56 NATO which see severe velocity loss in SBRs. The .300 Blackout provides better terminal performance than 5.56 while fitting the compact AR platform.

Range and Cost Limitations

While the .300 Blackout offers excellent versatility and performance, it does have some limitations to consider: Range and accuracy are not its strong suits compared to longer, higher velocity cartridges. The .300 Blackout experiences significant bullet drop beyond 300 yards, limiting its effective range. It is not well-suited for precision long-range shooting applications. Ammunition cost and availability can also be a drawback. .300 Blackout factory ammunition tends to be more expensive than 5.56 NATO, especially for premium hunting and match-grade loads. While selection is improving, it is still less widely available on the commercial market compared to more popular calibers. However, the .300 Blackout was never intended to be a precision long-range cartridge. Its design goals were to provide improved terminal performance and suppression capabilities in an AR-15 platform for short to medium ranges. Within that envelope, it offers a unique combination of traits not found in 5.56 NATO or other .30 caliber cartridges.
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Cartridge Comparisons

300 Blackout vs 7.62x39: Never Would've Guessed - YouTube
300 Blackout vs...
Here is a comparison of the .300 Blackout to other popular rifle cartridges: vs 5.56 NATO
  • .300 Blackout has significantly more energy and better terminal performance at all ranges
  • Excels in close-quarters combat (CQB) and suppressed shooting due to heavier bullets
  • 5.56 NATO has a flatter trajectory and longer effective range beyond 300 yards
vs 7.62x39mm
  • .300 Blackout and 7.62x39mm have similar ballistics in terms of energy and effective range
  • .300 Blackout has better accuracy and a higher ballistic coefficient for flatter trajectory
  • 7.62x39mm has slightly more case capacity and can push heavier bullets faster
vs .308 Winchester
  • Both fire .30 caliber/7.62mm bullets, but .300 Blackout is not as powerful as .308 Win
  • .308 Win has significantly more case capacity for higher velocities and energy
  • .300 Blackout is optimized for shorter AR-15 barrels, while .308 needs longer barrels
Overall, the .300 Blackout fills a niche between 5.56 NATO and .308 Win, providing excellent short-range performance from an AR-15 platform with subsonic suppression capabilities that those rounds lack.
Its ballistics are comparable to 7.62x39mm with some advantages in trajectory and accuracy.
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Supersonic Ballistics by Barrel Length

Here is a table summarizing supersonic .300 Blackout ammunition muzzle velocities and energies from different barrel lengths:
Barrel LengthBullet Weight/TypeMuzzle VelocityMuzzle Energy
9 in115 gr UMC2,120 fps1,136 ft-lbs
16 in115 gr UMC2,295 fps1,344 ft-lbs
9 in110 gr TTSX2,300 fps1,310 ft-lbs
9 in110 gr V-MAX2,350 fps1,350 ft-lbs
9 in125 gr OTM2,030 fps1,143 ft-lbs
16 in125 gr OTM2,215 fps1,360 ft-lbs
20 in78 gr Lehigh CQ2,880 fps1,436 ft-lbs
24 in78 gr Lehigh CQ2,960 fps1,517 ft-lbs
20 in90 gr Barnes OTFB2,630 fps1,382 ft-lbs
24 in90 gr Barnes OTFB2,710 fps1,468 ft-lbs
The .300 Blackout offers a wide range of supersonic loadings from lightweight 78 grain bullets at very high velocities over 2,900 fps, to heavy 220 grain subsonic ammunition under 1,000 fps. Typical supersonic loads use 110-125 grain bullets with muzzle velocities around 2,200-2,350 fps and energies over 1,300 ft-lbs from a 16" barrel.
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Ballistic Performance

The .300 Blackout offers excellent ballistic performance from the AR-15 platform. From a 16-inch barrel, a 125 grain bullet has a muzzle velocity around 2,215 fps and muzzle energy of 1,360 ft-lbs. At 200 yards, typical bullet drop is around 8-9 inches. Supersonic loads have an effective range out to 500 yards, while subsonic loads are effective to around 200 yards. Compared to 5.56x45mm NATO, the .300 Blackout has similar trajectories out to 300 yards but significantly more energy, penetration, and terminal performance at all ranges. It outperforms 7.62x39mm in ballistic coefficient and energy from similar barrel lengths. The larger .30 caliber bullet delivers devastating terminal effects on targets. With proper ammunition selection, the .300 Blackout provides excellent versatility - from suppressed subsonic rounds ideal for home defense, to barrier-blind supersonic loads capable of penetrating body armor at range. Its performance makes it well-suited for hunting medium game as well as tactical applications.
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Subsonic Capabilities

The .300 Blackout truly shines when using subsonic ammunition, which allows for extremely quiet operation when paired with a suppressor. Subsonic loads typically use heavy 200-220 grain bullets traveling around 1,000 fps, producing noise levels around 135-140 decibels when suppressed - roughly equivalent to a loud handclap. This makes the .300 Blackout one of the quietest rifle cartridges available when suppressed. The low velocity and heavy bullet weight provide excellent short-range terminal performance on targets out to 200 yards. While subsonic ammunition sacrifices some external ballistics compared to supersonic loads, it excels in certain scenarios where noise discipline is critical, such as home defense or military operations. The ability to quickly switch between super and subsonic ammunition in the same firearm is a major advantage of the .300 Blackout cartridge.
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Suppressor Compatibility

The .300 Blackout cartridge is highly compatible with suppressors due to its design characteristics. Here are some key points about using suppressors with .300 Blackout: Most .30 caliber suppressors rated for .308 Winchester/7.62x51mm NATO can be safely used with .300 Blackout. This includes popular models like the SilencerCo Omega 300, Dead Air Nomad-30, and others. The lower pressures of .300 Blackout compared to .308 make it suppressor-friendly. When using subsonic .300 Blackout ammunition, even pistol caliber suppressors rated for 9mm or .45 ACP can provide excellent sound suppression. The low powder charge and heavy bullets minimize noise significantly. The ability to shoot both supersonic and subsonic .300 Blackout through the same suppressor is a major advantage over 5.56mm NATO. 5.56mm suppressors must be designed for much higher pressures, making them louder with subsonic ammunition. Some suppressor manufacturers offer specialized end caps or front caps to optimize sound suppression specifically for .300 Blackout. This fine-tunes the suppressor's performance for this cartridge. Overall, the .300 Blackout's relatively low pressures and ability to cycle subsonic loads make it one of the most suppressor-friendly rifle cartridges currently available. Its versatility allows using a wide range of suppressors effectively.
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