When diving into the world of AR-15 platform rifles, a common debate arises: 5.56x45mm NATO versus 300 AAC Blackout. It’s tempting to declare one definitively “better,” but this is a comparison of apples and oranges. The truth is, neither cartridge inherently outshines the other. The optimal choice hinges entirely on your specific shooting needs and priorities. For over half a century, the 5.56x45mm has served as the primary military rifle caliber, stepping in after the era of the 7.62x51mm M14 in 1967. While categorized as an “intermediate” caliber, especially when viewed against the .30-caliber cartridges it succeeded (like the .30-’06 and 7.62x51mm), its six decades of service speak volumes. Dismissing the 5.56 NATO as weak or ineffective is simply outdated thinking, ignoring its proven track record in real-world scenarios. Such viewpoints often echo outdated firearm fallacies, like the notion of .45 ACP superiority over 9mm or a shotgun being the ultimate home defense weapon for everyone.
Understanding the 5.56x45mm NATO
A variety of 5.56 NATO ammunition types illustrates its adaptability across different shooting disciplines.
The 5.56x45mm NATO’s effectiveness is rooted in velocity. Initially issued with a 55-grain FMJ-BT bullet, this evolved to a 62-grain projectile upon NATO standardization in the 1980s. It’s a relatively light bullet propelled at high speeds, often achieving muzzle velocities at or exceeding 3,000 feet per second (fps). This high velocity translates to a flat trajectory, beneficial for accurate shooting at varying distances. For non-military applications, the availability of advanced bullet designs significantly enhances its terminal performance. Modern expanding bullets are engineered to penetrate barriers and reliably expand upon impact in soft targets. The Barnes TSX and TTSX copper solid bullets are prime examples of high-performance options, and extensive real-world use by law enforcement and civilians has validated their effectiveness.
Beyond terminal ballistics, the 5.56x45mm NATO is known for its minimal recoil, making it easy to shoot accurately and control rapidly. Furthermore, both the 5.56 NATO and its commercial counterpart, the .223 Remington (which shares external dimensions but is loaded to slightly lower pressures), enjoy widespread availability and affordability. The 5.56x45mm NATO stands as a versatile general-purpose rifle cartridge, capable for a wide range of applications, with the main exception of hunting very large game.
Evolution of 5.56mm ammunition showcasing bullet weight and design variations: 55-grain M193, 62-grain M855, 77-grain Mk 262 Mod 1, and 80-grain Open Tip Match.
Advantages of the 5.56x45mm
- Ubiquitous Availability: 5.56 ammo is readily found nationwide.
- Cost-Effective: Economical factory loads are abundant.
- Versatile Ammunition Selection: Options for match shooting, hunting, and personal defense are widely available.
- Flat Trajectory: High velocity contributes to a flatter shooting trajectory.
- Reputation for Accuracy: Known for its inherent accuracy potential.
- Effective Terminal Performance: Modern bullet designs provide excellent stopping power for personal protection.
- Effective Range: Capable of accurate shots beyond 600 yards with appropriate loads.
- Mild Recoil: Easy to manage recoil enhances shootability.
- Reloading Friendly: Straightforward to reload for handloaders.
- Military and Law Enforcement Standard: Continuous development of new and improved loads.
Disadvantages of the 5.56x45mm
- Subpar Subsonic Performance: Not designed for effective subsonic loads.
- Velocity Dependent Performance: Performance diminishes significantly with shorter barrels.
- Not Ideal for Large Game Hunting: Lacks the bullet weight and energy for larger game animals.
- Velocity-Reliant Terminal Ballistics: Terminal performance is heavily dependent on maintaining high velocity.
Exploring the 300 AAC Blackout
Diverse loading options for 300 BLK ammunition cater to specialized shooting needs.
The 300 AAC Blackout, or 300 BLK, operates in a different performance realm. Its lineage traces back to the .300/.221 Fireball (.300 Fireball) and the .300 Whisper®. The .300 Whisper, a .30-caliber wildcat based on the .221 Fireball, was conceived and trademarked in 1992 by the renowned gunsmith J. D. Jones. Jones envisioned a versatile cartridge for both single-shot hunting pistols and AR-15s, particularly for suppressed applications. He engineered the .300 Whisper as a dual-purpose cartridge, capable of firing lighter bullets (110 to 130-grain) at supersonic speeds and heavier bullets at subsonic velocities for suppressed shooting. His preferred subsonic load featured the 0.308-inch 220-grain Sierra MatchKing bullet at approximately 1,000 fps. Crucially, the 300 BLK shares the same overall cartridge length as the .223/5.56.
J.D. Jones was a pioneer in subsonic cartridges for suppressed firearms, ahead of his time in the 1990s when suppressors and even AR-15s were far less common. Interest in his work initially came from specialized military units and government agencies. For years, the cartridge remained a niche wildcat, known to few outside of these specialized circles.
The 300 BLK cartridge is designed to fit and function within standard AR-15 magazines.
Kevin Brittingham, founder of Advanced Armament Corporation (AAC) and current CEO of Q, shed light on the 300 AAC Blackout’s development and the iconic Honey Badger PDW. “We (AAC) were supplying suppressors to the U.S. Navy SEALs. They, along with Army special operations forces, had long sought the capability to fire 7.62x39mm ammunition through the M4 platform. However, the AR-15 magazine well makes this impractical. This led them to the .300 Whisper,” Brittingham explained.
He continued, “They were enthusiastic about the concept but encountered reliability issues and sought our expertise. Recognizing an ammunition problem, Remington, upon acquiring AAC, inquired about our interest in developing a solution. Their objective was to create both supersonic ammunition with AK-47-like performance and subsonic ammunition as quiet as possible, akin to the MP5SD.”
This collaboration culminated in the 300 AAC Blackout and the Honey Badger PDW. Remington prioritized the Blackout’s commercial potential for hunting and defense using supersonic ammunition. The initial supersonic load featured a 110-grain bullet traveling between 1,900 and 2,300 fps, depending on barrel length. Subsonic ammunition typically employs 200-grain bullets at or slightly above 1,000 fps. Subsonic 300 BLK exhibits minimal recoil, while supersonic loads generate approximately 25% more recoil than 5.56x45mm NATO.
Advantages of the 300 AAC Blackout
- Dual Supersonic/Subsonic Capability: Designed for both standard and suppressed applications.
- Optimized for Short Barrels: Excels in AR pistols and short-barreled rifles (SBRs).
- Superior Subsonic Performance: Subsonic loads are exceptionally quiet with a suppressor.
- Effective Supersonic Performance: Supersonic loads offer good terminal ballistics.
- AR-15 Magazine Compatibility: Feeds reliably from standard 5.56x45mm magazines.
- Minimal Subsonic Recoil: Subsonic loads have very low recoil.
- Designed for the AR-15 Platform: Specifically engineered for optimal AR-15 performance.
- Reloading Versatility: Easy to reload for a wide range of applications.
- Suitable for Hunting and Personal Protection: Versatile for various shooting scenarios.
- Ongoing Ammunition Development: Continuous advancements in load development.
Disadvantages of the 300 AAC Blackout
- Limited Long-Range Performance: Lower muzzle velocity makes it less effective at extended ranges.
- Higher Ammunition Cost: Ammunition is generally more expensive than 5.56x45mm.
- Potential Reliability Issues: Some firearms may experience cycling issues when switching between supersonic and subsonic loads.
- Handgun-Like Subsonic Terminal Performance: Subsonic loads offer terminal ballistics comparable to handgun cartridges.
- Expensive Subsonic Match Bullets: High-quality, heavy match bullets for subsonic loads can be costly.
To judge the 300 AAC Blackout by traditional rifle cartridge standards is to misunderstand its purpose. Skeptics focusing solely on supersonic specifications may find it underwhelming, noting ballistic figures slightly below a 7.62x39mm, which is itself not considered a high-powered cartridge. However, this perspective misses the 300 BLK’s design philosophy: optimization for short barrels, particularly 9-inch barrels. In the realm of AR pistols and SBRs, compact size is often paramount. The .223/5.56 cartridge suffers significantly in short barrels. A standard 55-grain 5.56 load achieves around 3,000 fps from a 16-inch barrel. Reducing barrel length to 7.5 inches, a popular ultra-short configuration, can drop velocity to approximately 2,200 fps. This nearly 30% velocity loss severely impacts a cartridge that relies on velocity for terminal effectiveness due to its light bullet. Furthermore, the muzzle blast and concussion from a short-barreled 5.56 are substantial.
The 300 BLK cartridge is optimized for short barrels, significantly outperforming 5.56 NATO in barrel lengths under 10 inches.
The 300 AAC Blackout utilizes powders specifically selected to maintain performance in short barrels. Bore volume is another key factor. An 8-inch 300 Blackout barrel has a comparable bore volume to a 13-inch 5.56x45mm barrel. The 300 BLK uses faster pistol powder, while the 5.56 relies on slower rifle powder. Comparing supersonic 300 Blackout velocities between 9-inch and 16-inch barrels reveals that the 9-inch barrel retains 90% of the velocity, despite being significantly shorter. While the 5.56x45mm NATO arguably serves as a more versatile “general purpose” cartridge due to its lighter weight, lower recoil, affordability, wider availability, and projectile selection, the 300 Blackout excels in specific niches. It is true that 5.56 is effective against deer, hogs, and threats to personal safety, and in longer barrels, it performs comparably to the 300 Blackout for most applications, except when greater mass is needed for barrier penetration or larger game hunting, where the heavier 300 Blackout bullets hold an advantage.
Recommendation
For AR pistols or SBRs with barrels shorter than 10 inches, the 300 AAC Blackout emerges as the superior choice, especially when compared to the 5.56x45mm, which suffers significant velocity loss below 11.5-inch barrels. Supersonic 300 Blackout ammunition is purpose-built for short-barreled ARs and demonstrably outperforms the 5.56 in single-digit barrel lengths. From a 5.5-inch barrel, a 110-grain 300 BLK achieves similar velocity to a 55-grain 5.56 NATO. Furthermore, for those prioritizing suppressed shooting, a suppressed AR firing subsonic 300 BLK ammunition offers unparalleled quietness in a semi-automatic platform, while retaining familiar AR-15 ergonomics.
If you have any thoughts or comments on this article, we’d love to hear them. Email us at [email protected].
