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.
Similar Posts:
- Why Shoot a 300 Blackout? Kirsten Provides Some Answers
- Horner Wins Tactical-Optics Divison At Multigun Nationals
- 300 AAC Blackout Load Data from Sierra Bullets
- Scary Stuff — .300 Blackout Fired in a .223 Rem Barrel
- Learn About 300 AAC Blackout with Articles and Podcast
Tags: .223 Rem, .300 AAC Blackout, 300 BLK, AR15, Lapua Brass, Suppressor
The question that I’ve always asked when I look at this is is why hasn’t someone figured out one can just as easily make a modern set of 125gr and 220gr 7.62×39’s and blow away the .300 BLK at it’s own game?
Though it’s a common report that subsonic ammo isn’t remarkably accurate for most users, I’ve been very pleased with my Remington 700’s performance with 208 AMaxs.
With a warm barrel/suppressor unit, it is possible to shoot impressive groups. Out of a cold unit, you will always have a flyer, usually the first shot.
Dennis, running 7.62×39 in an AR has a whole bunch of issues on its own.
Dennis- 300 BLK starts with a 5.56 casing that they neck down much shorter, allowing for a wider and longer bullet that can now weigh significantly more than any 5.56 can. And using the 5.56 casing and same length round (from casing base to bullet tip) means they can use 5.56 magazines with no capacity loss. 7.62 has a wider casing and requires different size magazines along with a different bolt. 300 BLK was a way to achieve similar ballistics as the .308- with the least modifications to your 5.56. All you need is a bigger diameter barrel. So you can ball on a budget and just buy the barrel and make the swap when needed-or buy just brand new upper already setup for 300 BLK and throw it on your existing lower. Either way you go it is cheaper and requires the least modifications-while providing far superior performance and effectiveness over 5.56 in certain scenarios.
Spend the money on a decent upper. It’s a 30 second swap from 300blk to .556
I have a Sig red dot on my 556 upper and a 4-12×40 Bushnell scope on my 300. Best of both worlds. I don’t shoot subsonic. FWIW.
Twist-rate!
7.62 x 39 usually runs in barrels with a 1:10″ (ish) twist. This is actually much tighter twist required to stabilize the short 124gn. bullets. It happened that way because when the Russians developed the round, all of their 7.62mm barrel making machinery was built to make 1:10″ twist barrels for a bazillion Mosin Nagants and a swag of machine guns in 7.62 x 54R. Note that they used exactly the same twist on the TT30 and TT33 auto pistols and millions of SMGs chambered in 7.62 x 25. It seemed to work OK for all those years.
However, if you try to shoot “custom” loaded 7.62 x 39 ammo loaded with a 220gn bullet from a 1:10 twist barrel, you will be disappointed because the bullet will not be DRIVEN fast enough to SPIN fast enough to stabilize correctly.
Thus, “proper’ 300 BLK and .300 Whisper, before it, run with tighter twist barrels. 1:8″ or increasingly, 1:7″, especially if you want to stabilize subsonic, LONG bullets at low temperatures. The LAST thing you want is a “wobbly” bullet going through your expensive muffler, not quite behaving itself.
Lighter, 125gn bullets won’t care, but long, slow bullets need FAST spin-rates.