Most ARs and similar rifles are chambered in either 5.56 or .223. This is likely not just a matter of convention but of the low cost and high availability of both these cartridges, particularly the former.
On top of that, it’s a solid round for a wide range of applications, from hunting predators to long-range shooting.
But .300 Blackout, new as it is as a replacement, beats it on several fronts. Here are just 5 of the best reasons to build your next rifle with a .300 Blackout AR upper instead of chambering it in 5.56 or .223.
1. It generates more stopping power and carries it further.
The .300 Blackout is a larger, heavier cartridge firing a bigger bullet than 5.56 and .223, and it generates more stopping power. It also has a higher ballistic coefficient and carries more energy to the target (within its effective range) than 5.56 and .223.
Take, for instance, a .300 Blackout cartridge loaded with a 110 grain bullet that leaves the muzzle at 2375 FPS compared to a 5.56 round loaded with 55 grain bullet that generates 2982 FPS of muzzle velocity.
The .300 BLK round will produce 1378 ft-lbs of muzzle energy to the 1086 ft-lbs of the 5.56. That’s clear enough, but what’s even more compelling is that 100 yards the former will retain 1071 ft-lbs whereas the 5.56 will have dropped to 825. It’s even worse at 200 yards, where the .300 BLK still maintains 821 and the 5.56 only 617.
The .300 Blackout generates more power and carries it farther, producing more stopping power at the close and intermediate ranges at which it is designed to perform.
2. It performs better from shorter barrels.
The .300 Blackout is arguably better for those who are interested not just in building carbines, but in building short-barreled rifles (SBRs) and AR pistols (ARPs). This is because it performs better from short barrels.
The 5.56 is a fast cartridge. The .300 BLK is slower but as a result, more of the powder charge can fully deflagrate in a shorter barrel.
Take the same load mentioned above and run it through a hypothetical 11” barrel, so an SBR build. The .300 BLK would produce 2221 FPS and 1205 ft-lbs and the 5.56 would outpace it at 2579 FPS but fall short, by a long way, at 812 ft-lbs.
So if you’re building an SBR or ARP, seriously consider the .300 Blackout.
3. You can probably reload old 5.56 cases to save money.
One of the parent cases of the .300 BLK is the .223 Remington, which means that with the proper tools you can neck out and trim old .223 or 5.56 cases and reload them as .300 Blackout, which should help you offset the high costs.
4. It shoots well suppressed.
In part because the propellant charge fully deflagrates with .300 BLK, it performs better not just from a shorter barrel but through a suppressor, and you’ll get less hot gas in your face from the port, too. It’ll shoot quieter and more smoothly when suppressed.
5. You can probably keep some of your other 5.56 AR parts.
A .300 Blackout AR upper will need a specific barrel, but you can use a lot of the same 5.56 AR parts with a .300 BLK build, such as the lower parts and BCG. Really, only the magazine and barrel need to be swapped, and perhaps the buffer weights, but that is something you can adjust after the fact.
Just Be Aware…
While there is a lot to appreciate about .300 BLK, it does carry a few considerations that you should keep in mind if you choose this cartridge.
.300 BLK costs more.
This is perhaps the least palatable aspect of building a rifle with a .300 Blackout AR upper, at least to a lot of shooters. The cost of .300 BLK compared to either 5.56 and .223 is significantly higher, and even if you get a deal on bulk, you probably won’t be able to make it more economical. Plus, there are surplus deals in addition to bulk deals on 5.56 that you likely won’t find with .300 BLK.
It’s not good for long range shooting.
As some say, .300 Blackout drops like a rock in a sock. You will want to keep shots within 200 yards, realistically within 100 yards. Past 300 is speculative at best and realistically shouldn’t even be attempted.
Start Your Build with a .300 Blackout AR Upper
As you can see, despite its few shortcomings, there are plenty of good reasons to choose .300 BLK over .223 or 5.56, or over a number of other cartridges, for that matter.
Explore our collection of .300 Blackout AR uppers and parts to get what you need for your next build, and if you have any questions about parts, components, or compatibility, get in touch with us.