Advanced Armament Corporation developed the .300 AAC Blackout in 2010 and released it with the intention of offering a .30 caliber cartridge with better performance than 5.56mm ammunition currently in use. Replacing the 5.56 NATO cartridge is an idea that has been around since its introduction, but the urgency rose with the Global War on Terror which rapidly placed many of our troops in harm's way across many different situations and unfamiliar geography.
The key motivator to consider replacing the 5.56 NATO was the increased terminal performance offered by a .30 caliber round. This alone, however, would not necessarily justify wholesale replacement of the primary issue rifle of the military. Any cartridge that replaced the 5.56mm would need to be compatible with the M4 weapon system. The .300 AAC Blackout is compatible with the M4 system since the case was built from the existing 5.56mm cartridge, allowing for the use of the same magazines from the M4 system, and to full capacity. To convert an M4 system rifle to .300 Blackout, the barrel is the only part that needs to be changed.
The noise of the .300 AAC is drastically reduced with the use of subsonic loads and a suppressor. Some describe the resulting noise levels as similar to the Heckler and Koch MP5-SD which fires 9mm ammunition. Coupled with a bullet about 40% heavier than the 9mm fired from the MP5-SD, and moving nearly 100 feet per second faster, the .300 Blackout dramatically outperforms the previous gold standard.
The max effective range of the .300 Blackout supersonic load is listed at 500 yards, and with the subsonic load, is listed at 220 yards. Muzzle velocity for the supersonic 125 grain FMJ bullet is 2,215 feet per second, and muzzle energy is 1,360 foot pounds. Muzzle velocity for the subsonic load is 1,010 feet per second, and muzzle energy is 498 foot pounds. Downrange, the .300 Blackout is accurate enough to deliver groups smaller than one inch at 100 yards.
The .300 AAC Blackout is a new cartridge with many positives, including its compatibility with the M4 platform. Additionally, it offers increased performance for both supersonic and subsonic applications, clear benefits for military applications. For the civilian market, the cartridge increases the versatility of the AR-15 platform that much more. Also, due to increased bullet performance, hunters can use the .300 Blackout for harvesting medium sized game animals. If those reasons are not enough, the .300 Blackout with fantastic accuracy and controllable recoil enabled SSG Daniel Horner of the US Army's Marksmanship Unit to use the cartridge to win the USPSA Multi-Gun Nationals in 2011. The .300 Blackout offers a great deal to all kinds of shooters and no doubt has a very bright future.