Building your own AR, or ARP, offers you a lot of flexibility with respect to how you can customize the build along the way. Plus, it’s a very enjoyable process.
But, as with all things in life, there is no magic formula. What you gain from a niche chambering, you will also trade off in other areas.
This is very noticeable with a .300 Blackout AR upper, which will offer you significant advantages over 5.56 (and .223). But these come at a price.
So, with no further ado, let’s balance two significant advantages of a .300 Blackout AR upper with two tradeoffs of the same.
First, the Strengths: Greater Stopping Power
Muzzle velocity is pretty much higher across the board for 5.56 rounds, but stopping power is solidly in the camp of .300 BLK, which produces muzzle energies roughly in the area of 1100 to 1300 ft-lbs.
These numbers will vary depending on bullet weight, barrel length, muzzle velocity and other load data, but regardless, .300 BLK produces more stopping power no matter how you slice it.
This makes the .300 BLK preferable for some builders who are interested in building a PDW platform, as it delivers more firepower, especially at close ranges.
Yet, being very similar to the 5.56, if loaded with an appropriate bullet, such as a soft point or hollow point, it produces relatively low risk of overpenetration.
.300 BLK Performs Well with a Short Barrel
Another massive advantage of a .300 Blackout AR upper is that, if you’re interested in building an ARP, you’re basically guaranteed better performance with the .300 BLK than with 5.56 NATO.
The 5.56 does not perform particularly well from short barrels, despite the fact that many AR15 pistols are chambered in it. As a result, they are loud, produce an enormous amount of muzzle pop, and a ridiculous amount of fouling as a result of incomplete deflagration in the chamber and bore.
These issues are mitigated somewhat by the .300 BLK, which performs shockingly well from short barrels, even barrels that are shorter than 10 inches.
This makes .300 BLK one of the top choices for those interested in building AR15 pistols, as it will produce not just better stopping power, but perform better from a shorter barrel without excessively fouling the gun.
Just bear in mind that .300 BLK will produce a bit more recoil, since the bullets are considerably heavier. That stopping power comes at a price.
Now the Drawbacks: Ammo Is Expensive
We won’t mince words here. The 5.56 is cheap and readily available, especially as surplus ammo. The same isn’t really true for .300 BLK. Not only is it a niche cartridge that can be somewhat hard to find, it is certainly not cheap.
If you buy surplus deals or in bulk, you can usually engineer the price of 5.56 FMJ down pretty close to 50 cents, in some cases even less, which is really cheap for a rifle cartridge.
That won’t be happening with .300 BLK unless you find some kind of generational deal. Even if you buy in bulk you will likely still pay close to a dollar, and if you buy in low quantities, you could pay a dollar per round if not more, especially if you shoot some sort of specialty ammo.
So keep that in mind. There are some big benefits of chambering in .300 BLK but you will pay for them, literally.
.300 Blackout Performs Abysmally at Long Ranges
Lastly, bear in mind that if you build with a .300 Blackout AR upper, you will not be building a long-range rifle.
Forget accuracy, which is also questionable. It’s the bullet drop that’ll get you. It’s been said, to quote, that .300 BLK drops like “a rock in a sock,” and it is sadly true.
The 5.56 is a flat shooter, but .300 BLK, depending on load data, can drop 100 inches or more at 300 yards with a 100 yard zero. So take that for what it’s worth, and keep your shots within 200 yards, if not within 100 yards, if you go with this chambering.
Start Your Build with a .300 Blackout AR Upper
While a .300 Blackout AR upper will not offer you straight advantages across the board, the performance from short barrels, willingness to run reliably suppressed, and greater stopping power offset the high cost and poor performance at greater ranges, at least to some shooters.
If you’re in that camp and consider those drawbacks to be palatable, start your next build with a .300 Blackout AR upper, especially if better stopping power and performance from a short barrel are at the top of your list in terms of performance.
Explore our collection of .300 Blackout AR uppers and .300 BLK rifle parts, and get in touch with us at Sales@MCSGearup.com if you have any questions.