.300 AAC Blackout Cartridge: Perfect for AR-15s

Why should you consider an AR in .300 AAC Blackout rather than 5.56 NATO? If you only have one AR-15 then I recommend 5.56. However, if you already have a 5.56 or are looking specifically for something you can use hunting pigs and medium size game, then a .300 BLK is a viable option. If you are looking to shoot suppressed, well the .300 BLK is hard to beat.

While the .300 BLK cartridge has been with us for about a decade, the concept is much older. Perhaps the best known predecessors are the .300/.221 Fireball and .300 Whisper from JD Jones.

Both of these are wildcats and never really made a big splash. In 2010 though Robert Silvers, the Research and Development Director of Advanced Armament Corp. (AAC), was contacted by a government customer with a requirement for a cartridge firing a .30 caliber projectile capable of being chambered in a M4 carbine.

He was asked if AAC could produce firearms with Remington Defense manufacturing .300/.221 Fireball-type ammunition. This request would lead directly to Silvers developing what became the .300 BLK cartridge.

I have known Silvers for almost 20 years now, so to get the story on the origins of this cartridge I contacted him directly. What follows is, in his words, how the cartridge was developed:

“With Remington already doing the .221 and .17 Fireball, it was a natural to do the .30 caliber. But Remington is a SAAMI company and only makes SAAMI approved ammunition. So we had to create the final specifications of the cartridge, and seek SAAMI acceptance.

“The problem with calling it the .300 Fireball was two-fold. One is that the cartridge is low visibility, and Fireball seems like the opposite of that. The other is that there were too many chamber drawings for wildcat versions called .300 Fireball. If we picked that name, we would have to clear compatibility with these existing chambers, and that would limit velocity potential because we would have to pressure-test the ammo in the tightest one.

“.300 Whisper is a proprietary name which requires licensing, and SAAMI does not accept trademarked names. Also, I did not want to use it because it implies subsonic is the primary use—and that is not the way I see the cartridge. 300 AAC Blackout was designed to be the most powerful way to shoot .30 caliber from an AR-15 while remaining compatible with normal 30-round magazines. A fresh name was needed so that we could design the chamber with the exact specs we thought best. 300 AAC Blackout is a name both consistent with full power ammo, but yet stealthy at the same time.”

And just what was the new cartridge developed for and intended to do? The goals of the project were fairly straightforward:

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• Create a reliable .30 caliber cartridge compatible with the AR platform.
• Create the optimal platform for sound and flash suppressed fire.
• Develop supersonic ammunition which matches 7.62x39mm ballistics.
• Provide the ability to penetrate commonly encountered barriers.
• Utilize existing M16 magazines at their full capacity.
• Encapsulate these capabilities in a lightweight, low recoiling yet durable package.

Silver’s solution requires only a barrel change to convert from 5.56 to .300 BLK. Existing 5.56 AR bolts and magazines can both be utilized. By using the standard-size bolt, the locking lugs are not weakened as happens with cartridges that require a larger bolt face. So this problem is eliminated. By using a standard 5.56 magazine the need for expensive proprietary magazines is eliminated.

The .300 BLK’s performance is a bit different than conventional rifle cartridges in that it offers two distinct levels of performance. A shooter can select either heavy (200 to 240+ grains) subsonic loads or lighter (110 to 140+ grains) supersonic loads.

Subsonic loads are simply those that drive their projectiles at less than the speed of sound. The speed of sound in dry air at 68 degrees is 1,126 fps. Heavy efficient projectiles with high ballistic coefficients retain their velocity and energy well. So despite their low initial velocity, a 200+ grain .30 caliber subsonic load can provide acceptable performance on medium size game. More importantly it can do this, when teamed with a sound suppressor, at a very pleasant and safe noise level.