300 Blackout Basics — Specs and Cartridge INFO

As the .30-Cal cartridge of choice for the AR15 platform, the 300 AAC Blackout, also known as 300 BLK, has become quite popular with black rifle owners. You can now purchase quality factory ammo and even premium Lapua 300 BLK brass. Some folks wonder — “why consider a 300 BLK”? Here are the key reasons you may want to acquire a 300 AAC Blackout upper for your AR:

FIVE REASONS to Shoot the 300 BLK:

1. Easy Conversion: Use your current AR lower, bolt/carrier, buffer, and magazine. The only part you need to change is the barrel.
2. Hunting Capability: 300 BLK conforms to state hunting regulations which may require a cartridge larger than .22 caliber. The 300 BLK shoots .308 caliber bullets.
3. Suppressor-Friendly: You can shoot heavier bullets subsonic. The subsonic capabilities of the 300 BLK make it ideal for use with a suppressed AR.
4. Great Barrel Life: With a .30-caliber bore and a modest powder charge, barrel life is outstanding.
5. Great Brass: No Case forming is required — just buy Lapua 300 BLK brass.

The 300 AAC Blackout was created by Advanced Armament Corp. and Remington primarily for the military as a way to shoot .30-caliber bullets from the M4/AR15 platform while using standard magazines. As explained by Robert Silvers, AAC’s R&D Director: “[You can] shoot 30 caliber from your AR while still using normal magazines with full capacity. Even the bolt stays the same, and all that changes is the barrel.” CLICK HERE for more information.

The concept of putting a .30-caliber bullet in a shortened 223 case has been done before, but not as an industry-wide standard that anyone can make products for, royalty-free. SAAMI, the industry standards organization, adopted and standardized the AAC 300 Blackout earlier this year. The SAAMI diagram for the 300 BLK is shown below.

300 Blackout SAAMI Cartridge Specification

Affordable Factory 300 BLK Ammo is Available
Remington now sells a variety of 300 BLK ammo: 1) 125 grain open-tip match with a custom Sierra bullet; 2) 220gr subsonic, and 3) 125gr AccuTip (photo below). While the 300 BLK is easy (and inexpensive) to reload, Remington and AAC recognized that most people are not reloaders. So Remington will be budget-priced UMC-brand 300 BLK ammo through at just $12.99 per box — that’s less than most other rifle cartridges than are more powerful than the .223.

The 300 AAC Blackout definitely works for hunters who want to use their AR15-platform rifle. And it also serves as a specialized 30-Cal “rule-beater” that lets 3-Gun competitors “make major” with a low-recoil cartridge that also offers long barrel life. For those who need to run a .30-caliber cartridge from a standard AR15 platform (as opposed to the AR10), the 300 AAC Blackout makes sense. But for hunters using a bolt gun, there are any number of tried and true options, such as the 7.62×39, .30-30, and, of course, the .308 Winchester (7.62×51 NATO).

WARNING: With some bullet options (and setback during chambering) 300 Blackout rounds will go into a .223 chamber and fire. Putting a .308-caliber bullet in a .224-diameter barrel is a recipe for disaster. You can blow up your gun and sustain serious injury. That’s why we recommend you have a dedicated 300 BLK upper and mark your magazines. Also, always, always check your .223 magazines to ensure no 300 BLK rounds worked their way in when you loaded the mags. There have been a number of Kabooms recorded from 300 BLK rounds fired in a .223 Rem/5.56×45 chamber. CLICK HERE to see actual 300 BLK in .223 Rem chamber.

Other 300 BLK Resources
300 BLK by AAC: An Introduction by Paul Erhardt.
300 AAC Blackout Ammo Review
AAC .300 BLK AR-15, The Gun Blog.