Time to cut through all of the chatter.
The .300 Blackout (BLK) has been called everything from the 5.56 killer to the black mamba.
It was designed by Advanced Armament Company (AAC) to be a replacement for the MP5SD, a 9mm sub-machine gun favored by special ops. But it had to have more power, the same sound level, and compatible with the M4/AR-15.
The 300 BLK did exactly that…and gave us civilians a serious upgrade for the AR-15.
But just because it’s there doesn’t mean it’s necessary.
We’ll look at the ballistic, costs, and real-world killing power of each cartridge. Then make recommendations on when to use which.
Why the AR-15?
To really understand why the 300 BLK round is such as step forward you have to understand the AR-15.
The AR-15 is the most popular sporting rifle in America because of it’s ease of use and customization. If you want to know everything about the AR-15, check out our Buyer’s Guide.
The 300 BLK gives the AR-15 the ability to shoot a much larger bullet (similar to the 7.62x39mm round used by the AK-47) by switching out the upper receiver.
No changes are needed to the lower receiver or even magazine. If you want, you can only switch out the barrel since the bolt will stay the same.
Once You Go Black
In March of 1965 the United States would enter in a war that would change the way we fought forever.
Troops were dropped into the jungles of Vietnam with M14 rifles chambered in 7.62 NATO. (.308 Win).
The long heavy rifles dominated the long engagement distances that were common in WW1 & WW2 but now the troops found them so close to the enemy they were ordered not to even use grenades.
The answer was a black rifle called the M-16 (full-auto) chambered in a short, fast round called the 5.56 NATO (.223 Remington). This enabled soldiers to carry more ammo because it was significantly less weight compared to the 7.62 NATO round.
The AR-15 is its civilian semi-auto cousin with a shorter barrel (normally 16″ vs 20″ of the M-16).
The only problem was, and still is, the anemic 5.56 round leaves a lot to be desired.
Obstacles, glass, wind, body armor, or extended range can all drain performance with standard ball, or full metal jacket (FMJ) ammo.
How We Made the .300 AAC Blackout
The 300 BLK has its origins in the 300 Whisper, a round designed…as the name suggests…to be shot suppressed.
The case is formed by stretching out the case of a 5.56 NATO and trimming it down slightly.
It is then stuffed with fast burning powders and any number of bullets weighing from 110-220 gr.
What you have now is, the ultimate short range thumper that will feed both supersonic and subsonic ammunition and get its full ballistic potential (complete burn of the powder) from a 9-inch barrel.
The .300 BLK is really what two long protracted wars in the Middle East have taught us about what is needed in the average modern gun fight.
A hard hitting, short, light, and quiet gun that will own 0-300 yards.
The AR-15 with .300 BLK does this markedly better than the 5.56 but doesn’t always beat it out for every job.
.300 Blackout vs 5.56/.223
|Common Bullet Weights||40gr-77gr||110gr-220gr|
|Availability||Very Common||Somewhat Common|
|Cost||$.25-1.50 per round||$.50-3.00 per round|
Round 1: Strengths & Weaknesses
Both calibers are used for the same general purpose.
An intermediate class rifle cartridge for target shooting, hunting, home defense, and plinking.
However, they both have their strengths.
The 5.56 is half the cost of 300 BLK and is available in more high-end loading suitable for precision rifle fire.
The 5.56 also shoots flatter, has less recoil, and the ammunition weighs about 40% less.
The 5.56 is also safer for use inside a building for home-defense because the rounds are designed to break apart upon impact.
The “High Velocity Projectile Fragmentation and Deformation Theory” the military envisioned actually works!
The .300 BLK has a wider range of projectile choices, thanks to the .30 caliber bore, burns its full potential in a 9-inch barrel, and is a much better choice for hunting.
It also has the ability to cycle both super and subsonic ammunition without modification.
The .300 BLK shows its strengths when short barreled rifles and silencers are involved as well as when barrier penetration might be needed.
For a duty rifle that will conduct CQB work, this cartridge is a godsend.
Round 2: Exterior & Terminal Ballistics
|0 Yards||100 yards||200 yards||300 yards|
|5.56 20” Barrel||55gr @ 3100fps||0”/ 919 ft. lbs.||-3”/ 711 ft. lbs.||-12”/ 542 ft. lbs.|
|5.56 16” Barrel||55gr @ 2800fps||0”/ 742 ft. lbs.||-4”/ 567ft. lbs.||16”/ 426 ft. lbs.|
|300 BLK 9” Barrel||125gr @ 2100fps||0”/ 993 ft. lbs.||-8/799 ft. lbs.||-29”/ 641 ft. lbs.|
|300 BLK 16” Barrel||125gr @ 2240fps||0”/1312 ft. lbs.||-5.9/1068 ft. lbs.||-21/ 882 ft. lbs.|
|300 BLK 9” Barrel||220gr @1000fps||0”/461 ft. lbs.||-35”/ 437 ft. lbs.||-109”/ 416 ft. lbs.|
*50 Yard zero
In the table above you can see the compared ballistics of both the 300 BLK and the 5.56 NATO.
It shows the barrels that the cartridges were designed around…20-inches for the 5.56, 9-inches for the .300 BLK, and the most popular civilian barrel length of 16-inches.
Exterior ballistics are the qualities associated with how a projectile flies through the air.
The wind drift, bullet drop, and zero range all fall into the category of exterior ballistics.
You can see above that the 5.56 is significantly flatter than the 300 BLK in flight.
This is due to a faster velocity.
The .300 BLK uses bullets with a higher ballistic coefficient but isn’t moving fast enough to take advantage of its sleeker projectiles.
This is why the 5.56 shoots flatter, with less wind drift despite having almost half as much energy.
Terminal ballistics of a round are the qualities it has when it hits the target.
Its sectional density, the relationship of its mass and its weight, its ability to penetrate rather than fragment, and the wound channel it creates due to its bore size are all the study of terminal ballistics.
It’s important to note that while energy numbers can give you an idea of power around is, it’s only a single data point.
To the untrained observer the 300 BLK seems to have the edge in terminal ballistics.
The stouter bullets, with more mass of a larger caliber are seem to be the more effective round.
While the 300 BLK does have slight obstacle defeating capabilities it isn’t markedly better in performance than the 5.56 with the correct loading.
Modern bullet design is closing the gap between calibers and making the smaller bores more and more effective.
Additionally, the 5.56NATO was designed to break up, tumble and flip end over end when it encounters a target.
This is called high velocity projectile fragmentation and deformation.
All varmint style bullets follow this, and for bullets designed for Military or Law enforcement it’s very effective.
Any of the stories you hear of the 5.56 “poking holes in people” come from the steel core M855 round that was designed to defeat soviet body armor.
Any of the civilian, and all of the premium bullets designed for the 5.56 are good to go.
As far as a clear cut winner goes, it’s hard to tell. Depending on what you need the round to do, it’ll do it well.
Understanding Subsonic vs Supersonic Ammo
Super-sonic ammo is ammunition that travels faster than 1,000fps
Sub-sonic ammo is ammunition that travels slower than 1,000fps
The speed of 1,000 fps is important because that is the approximate speed of sound at sea level.
When a bullet travels faster than the speed of sound the bullet makes a crack, called a sonic boom.
This sonic boom is half of a gunshot sound; the other half is from the explosion of the powder.
The silencer (or suppressor) controls the explosion but has no effect on the sonic boom, which makes a silencer less effective.
If the goal is to have the quietest gun possible you need an effective silencer and subsonic ammunition.
This is a great combination for a home defense gun but terrible for anything past 25 yards or so. The reason being is that a 220gr bullet traveling at 1000fps is essentially a .45acp.
You should never hunt with subsonic 300 BLK ammunition as not only will it not get the job done…you’ll more than likely lose your animal.
You can’t count on the trajectory or the penetration of the subsonic ammo to place an ethical shot on a game animal past bad breath distance.
Stick to the supersonic 150gr or 125gr bullets and you’ll identical performance to a .30-30 or 7.62×39.
This is the section where you let random “experts” on the internet make recommendations on what you should shoot.
Sounds like fun? Great!
Target shooting, training, or informal plinking, shooting is just plain fun.
It can get expensive so this round goes to the 5.56.
The 300 BLK’s lethality and stopping powers just isn’t needed when all you’re doing is punching paper.
Look for bulk cheap 5.56 and use it and if you feel like you need to, switch to .300 BLK when the time comes.
Or if you’re Mr. Money Bags.
A man’s home is his castle and for keeping the peace you should walk softly and carry a stick chambered in 300 BLK.
The ability to have a 9-inch barreled gun with a suppressor and subsonic ammunition in a home defense situation means the difference between having hearing or not.
The .300 BLK is still great when you either can’t or care not to have NFA firearms.
If you find yourself in a state like California where you have a tight magazine ban and zero NFA goodies, get the bigger bullet.
If you’ve only got 10 rounds make it the best 10 you’ve got!
The only exception is if you live in a densely populated area, in an apartment, or have kids in the home.
Every round you send down range has a lawyer attached to it, you want to give those lawyers as little an excuse as possible to sue you.
The 5.56 readily breaks up in wall boards and loses power quicker when encountering barriers.
The answer to which caliber you should take hunting is a trick question.
With modern bullet designs the gaps between the killing power of calibers is shrinking.
If your quarry will include only small game or predators, then go for the 5.56. The wide range of factory loading for predator hunting edges out the 300 BLK.
If you plan on hunting medium or large game such as deer, hogs, or smaller bears, the 300 BLK is far superior.
The extra mass gives more reliable penetration than the 5.56 and the typical hunting ranges of these animals means that the slight disadvantage of trajectory is negligible.
Uppers available for cheap online can make your weapons much more versatile.
The best options to shoot both calibers.
Because the 300 BLK is derived from the case of the 5.56, all you have to do to switch caliber is to change the barrel. In an AR-15 the best way to this is to get another upper receiver.
Keep all your mags, your high quality bolt, use the lower receiver you have, and take advantage of both cartridges.
The .300 BLK won’t ever supplant the 5.56 for the most ubiquitous AR-15 cartridge but it does have some key areas where it really shines.
Chime in below…who can think of a time where you wish your AR-15 had a little more juice?