Recently, the .300 Blackout, also known as .300 AAC Blackout and .300 BLK, has become a popular alternative to the ever-present 5.56x45mm NATO.
If you’re thinking about starting your next build with a .300 BLK upper (who knows, maybe you already have a 5.56 and are looking for something new) here are some things to take into account.
Why Is .300 Blackout So Popular?
It’s hard to limit the popularity of .300 Blackout to just one, or even a few attributes, but here are a couple.
It is designed to offer better penetration characteristics than 9mm from similar barrels while being compatible with standard .223/5.56 mags (albeit standard mags can only hold lower capacity).
It also provides a bump in short range penetration and stopping power over 5.56 without producing much more recoil or necessitating an upgrade to a much heavier round.
Is .300 Blackout More Powerful than 7.62?
The 7.62x51mm NATO cartridge produces, on average, almost double the energy of the .300 BLK, so this 7.62 round is substantially more popular.
However, if you’re looking at the other 7.62, 7.62x39mm, AKA 7.62 Soviet, then performance is actually almost identical. This makes .300 BLK a popular alternative to this Russian round.
Is .300 BLK Good for Defensive Applications?
That depends on what defensive applications you are talking about. Since it’s a rifle caliber, it’s no good for concealed carry. But for home defense, the .300 BLK offers a lot to love - substantially increased performance over 5.56, especially within 100 yards.
So if you’re looking at close engagements, then the .300 BLK is not only a good, but a great, defensive cartridge.
What Game Animals Is .300 BLK Effective on?
Since .300 BLK offers substantially improved ballistic performance (at close range) as compared to 5.56, it is effective on basically all game that .223/5.56 is effective on, including small game, varmints, and medium sized predators like coyotes and foxes. Be warned, though, it is far too powerful to use for these applications if you expect to recover anything.
It’s much more effective at close to medium ranges on medium-sized game like deer and hogs, and with proper shot placement is actually fairly appropriate for them. There are even some that claim that .300 BLK is appropriate for defense against large predators like bears. With proper shot placement, it can definitely be effective.
Is .300 BLK More Effective than 5.56?
That depends on your definition of effective. It has both advantages and disadvantages within the scope of comparison.
Here’s how .300 BLK is arguably better than 5.56. It produces more stopping power at closer ranges, making it more effective against hostile targets at those close ranges.
Here’s where one might say 5.56 has .300 BLK cornered. It is lighter, cheaper, more readily available, produces less recoil (albeit hardly noticeable) and it is far more effective at greater distances since .300 BLK drops fast after 100 yards.
Can a 5.56 Rifle Chamber a .300 BLK Round?
No, you should never attempt to fire a .300 BLK round through a 5.56 rifle or you will encounter a potentially life-threatening and catastrophic failure of the platform.
Are Any Parts Interchangeable?
Technically, you can use all parts for a 5.56 rifle with a .300 BLK except for the barrel and gas system. Everything else for a 5.56 AR-15 rifle should also work with one built with a .300 BLK upper.
So, in theory, you could convert a 5.56 rifle to .300 BLK by swapping the barrel and gas system. You might also want to adjust the buffer weight, too (note below).
Will .223 Mags Work with .300 BLK?
Yes, standard .223/5.56 AR mags will work with .300 BLK, but they won’t be able to hold as many rounds. Usually a standard AR mag will hold a couple fewer rounds.
If you do use your .223/5.56 mags with .300 BLK make sure you keep them very carefully marked and separated and never stored in the same place, as accidentally chambering a .300 BLK in a 5.56 or .223 can be extremely dangerous.
What Buffer Weight Should I Use with a .300 BLK Upper?
While the bolt carrier group and buffer tube system of a rifle technically do not need to change, the buffer weights you’re accustomed to with 5.56 or .223 may not offer ideal performance with a .300 BLK.
It will depend on your barrel length and gas system, but you may get better performance (and reduced recoil) from a slightly heavier buffer weight. Contact us if you have specific questions.
Are There Any Things That .300 BLK Is Not Good for?
While a rifle built with a .300 BLK upper can be effective for hunting and defensive applications, it’s honestly, a pretty bad round for long-range shooting.
Even though most .300 BLK bullets will drop only about 4” at 100 yards, they will also drop like 2.5’ at 200 yards and 8’ at 300 yards. At 500 it’s even worse - most .300 BLK bullets will drop by close to 30’.
So stick to close and intermediate range applications here.
Is It True That You Can Reload .300 BLK from .223/5.56 Brass?
It depends on the thickness of the brass, but it is possible if you have a reloading setup with equipment that can neck out the cartridge to the appropriate dimensions; the cartridges are, otherwise, the same. Only the bullet and bullet diameter are different.
Why Is .300 BLK Ammo So Expensive?
There are a few things that keep .300 BLK expensive. One is that it is new and there are only a few ammo manufacturers that load it. This keeps supply fairly low - but demand is very high for this new cartridge. Altogether, this keeps prices up.
Getting Started with a .300 BLK Upper
Getting ready to start your next home built rifle with a .300 BLK upper. Keep in mind that many of the parts you have on hand may also be compatible, which can streamline the build. All the same, we carry everything you need for customizations piecemeal if you aren’t building with an assembled upper. Get in touch with us at Sales@MCSGearup.com if you have any questions before buying.