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The 300 AAC Blackout

The .300 AAC Blackout (aka 300 BLK, 300 Blackout, and 7.62 x 35mm) cartridge was developed by Advanced Armament Corporation and submitted for standardization to the Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI) and approved in 2011. The 300 BLK was developed response to requests from the military for a standardized cartridge with more energy on target and “punching” power than the standard 5.56 NATO AR-15 at close and medium ranges while maintaining the standard 30 round magazine of the government issued M4/AR-15 rifles. The 300 BLK is able to achieve this shortening a .223 Remington/5.56mm brass case and then “necking” up the brass case to utilize a larger, heavier .308”/7.62mm diameter bullet, rather than a .224”/5.56mm diameter bullet. Since the 300 BLK still shares the same case head dimensions as the .223 Remington/5.56 mm NATO cartridge, it allows use of the same bolt carrier group and magazines as a standard M4/AR-15, it makes conversion from from .223/5.56mm as simple as swapping the barrel and muzzle device. This has made the round extremely popular with the civilian AR-15 market as both for target shooting and hunting.

Despite being a 30 caliber rifle, the 300 BLK should not be confused with or compared to other 30 caliber rifles such as .308 Winchester, or .300 Winchester Magnum. Since the 300 BLK is using a larger bullet in a shortened brass case it has significantly less powder capacity than even .223 Remington. This limited powder capacity of 300 BLK restricts this cartridge to a max effective range of about 500 yards. The light powder capacity of 300 BLK allows this cartridge to achieve full powder burn in a barrels as short as 8”. This makes this cartridge perfect for AR’s built in pistol and short barreled rifled configurations. The 300 BLK cartridge when loaded to supersonic velocities using 110 to 125 grain weight bullets still reaches velocities up to 2300 fps giving the 300 BLK ballistics comparable to the standard AK-47 round, the 7.62 x 39mm. The 300 BLK can also be loaded subsonic velocities with heavier bullets from the 180 to 240 grain weight range. Being loaded sub- sonically to velocities below the speed of sound removes the supersonic “crack” as the bullet leaves the barrel makes this round inherently quiet with sound levels comparable to .22 LR. This also makes this an excellent choice for a dual tax stamp AR build using a short barreled rifled and suppressor configurations. Since the 300 BLK can be used out of shorter 10” barrel and still maintain muzzle energy comparable to 5.56mm in a 16” barrel, it can save the excess weight of 6” of the barrel. The 300 BLK’s accuracy and compact size makes this an excellent choice for hunters using AR-15’s and also bolt action rifles chambered for the cartridge.

One of the potential drawbacks of the 300 BLK can be ammo cost. Since the 300 BLK is still a relatively new cartridge and is not currently a military standardized round so surplus ammunition is not available like it is for 5.56mm. Many shooters have tried to mitigate the cost per round by loading their own 300 BLK ammo, however, this still requires an investment in reloading equipment if you don’t already reload. New 300 BLK commercial brass is also still expensive making savings going this route unrecognizable until you can load a few thousand rounds to make up for the initial investment. Many people have resorted to converting their own 300 BLK from cutting down their own .223 Remington cases and forming their own 300 BLK cases with sizing dies, however, this requires the neck of the case to be very uniform and can be a very tedious and dangerous job for an inexperienced hand loader. Another option has been purchasing remanufactured ammunition such as the offerings from Peak Performance using commercially remanufactured brass that can help keep ammunition costs to a minimum and quality high.