What Is .300 Blackout

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Last updated: April 10, 2026

Quick Answer: The .300 Blackout (300 BLK) is a rifle cartridge developed in 2011 by Advanced Armament Corporation for AR-15 rifles, engineered specifically for subsonic suppressed fire. It operates effectively at 1,000-1,050 feet per second when subsonic or 2,200+ fps when supersonic, offering versatile performance in a single platform.

Key Facts

Developed in 2011 by Advanced Armament Corporation (AAC) specifically for suppressed AR-15 rifle applications
Subsonic rounds travel at 1,000-1,050 feet per second, producing minimal sound signature when used with suppressors
Supersonic variants achieve 2,200+ feet per second velocity with ballistic energy comparable to 7.62x39mm (AK-47 ammunition)
Uses necked-up .223 Remington cartridge cases with .308 inch bullet diameter, enabling AR-15 platform use with only barrel/bolt changes
Adopted by U.S. Special Operations Command (SOCOM) in 2011 and utilized by military special forces and federal law enforcement

Overview

The .300 Blackout (300 BLK or .300 AAC Blackout) is a modern rifle cartridge introduced in 2011 by Advanced Armament Corporation, a leading suppressor and ammunition manufacturer. Designed specifically for the AR-15 platform, this cartridge revolutionized suppressed rifle technology by offering exceptional performance at subsonic velocities while maintaining versatility for supersonic applications.

The cartridge was engineered to solve a critical tactical challenge: delivering true subsonic performance with sound suppressors while maintaining effective terminal ballistics and reliability. Unlike the standard .223 Remington, which struggles at subsonic velocities, the .300 Blackout was purpose-built for this role, making it the preferred choice for military special operations and tactical professionals worldwide.

How It Works

The .300 Blackout's effectiveness stems from its intelligent ballistic design and ammunition versatility:

Subsonic Operation: Subsonic .300 BLK ammunition travels at approximately 1,000-1,050 feet per second, deliberately remaining below the 1,125 fps sound barrier. When paired with a suppressor, this produces sound levels of 130-145 decibels—comparable to an air rifle and the quietest rifle configuration available for tactical applications.
Supersonic Performance: Supersonic .300 BLK rounds reach velocities of 2,200-2,600 feet per second with bullet weights ranging from 110 to 220 grains. This performance envelope provides ballistic characteristics equivalent to the Soviet 7.62x39mm cartridge (AK-47 ammunition) while maintaining complete AR-15 platform compatibility.
Case Design Innovation: The cartridge ingeniously uses .223 Remington cases necked up to accept .308 inch (7.62mm) diameter projectiles. This design maintains structural integrity while minimizing case capacity, allowing standard AR-15 receivers, magazines, and components to function without modification—only the barrel and bolt carrier group require replacement.
Ammunition Flexibility: The same rifle platform accommodates both subsonic and supersonic ammunition without adjustment. A shooter can transition from suppressed subsonic operations to extended-range supersonic shooting simply by changing ammunition types, eliminating the need for separate weapon systems.
Ballistic Consistency: Subsonic loads use heavier bullets (190-220 grains) to maintain stable flight at transonic speeds, while supersonic loads employ lighter projectiles for higher velocity. Both variants maintain reliable cycling in direct impingement AR-15 rifles, ensuring operational dependability.

Key Comparisons

Cartridge	Muzzle Velocity	Effective Range	Primary Advantage
.300 Blackout (Subsonic)	1,000-1,050 fps	100-200 yards	Minimal sound signature with suppressors
.300 Blackout (Supersonic)	2,200+ fps	300-600 yards	7.62x39 performance in AR-15 platform
.223 Remington	3,000-3,100 fps	400-600 yards	Lower recoil; widespread ammunition availability
7.62x39mm	2,350-2,400 fps	300-500 yards	Non-proprietary cartridge; widely available globally
.308 Winchester	2,680-2,800 fps	800+ yards	Extended range capability; superior ballistic coefficient

Why It Matters

Military Adoption: The U.S. Special Operations Command (SOCOM) officially standardized the .300 Blackout in 2011, issuing purpose-built rifles to special forces units. Military and federal law enforcement agencies have adopted the platform for close-quarters combat, building clearance operations, and covert tactical deployments where noise discipline is essential.
Suppression Excellence: The defining strength of .300 Blackout is seamless suppressor integration. Subsonic ammunition produces sound signatures comparable to subsonic .22 Long Rifle firearms—a decisive advantage in operations where hearing protection is impractical or noise discipline prevents detection and localization.
Civilian and Hunting Applications: Beyond military use, .300 Blackout has gained significant civilian adoption among sport shooters and hunters. The subsonic variant excels for pest control in noise-sensitive areas, while the supersonic variant effectively takes deer-sized game with an AR-15 platform that many shooters already own and are proficient with.
Platform Efficiency and Cost: Converting an existing AR-15 to .300 Blackout requires only a barrel change and bolt carrier group swap, preserving the lower receiver, stock, trigger group, and magazines. This efficiency makes the platform accessible and economical compared to purchasing entirely separate weapon systems for different roles.

The .300 Blackout represents sophisticated engineering addressing specific operational requirements. Its dual-purpose design—delivering effective performance across subsonic and supersonic scenarios through intelligent ballistic engineering—has established it as a purpose-built cartridge with genuine practical advantages. From military special operations to civilian hunting and sport shooting, the .300 Blackout continues to demonstrate the enduring value of specialization in ammunition design.