Thinking about building an AR pistol? Well, before you knee-jerk and get an AR pistol build kit chambered in 5.56, take a few seconds to pause and read this post. Many AR shooters may consider 5.56 to be “old reliable” and it is in many ways a standard, but there are better chamberings for an ARP, notably 9mm Luger and .300 Blackout.
Though these cartridges are very different from each other (and from 5.56) they each offer something unique in terms of performance over both 5.56 and .223. Here’s what you should know.
9mm Luger
The 9mm offers a few things that 5.56 does not, which can make it a highly practical chambering for an AR pistol build kit.
First, let’s just talk about price. If you buy bulk deals or look for police trade-in specials, you can often get such great deals on 9mm that you can beat the price of 5.56 in bulk. They’re fairly comparable, especially on availability but if you do a lot of high-volume target shooting 9mm can be even more affordable.
Then there’s recoil and suitability for the recoil-sensitive, beginners, or smaller-framed shooters. The 9mm produces less recoil than 5.56 (not that the latter is a particularly hard-kicking round, but this should be considered) making it more practical on that front. This is all the more thrown into relief when you consider that recoil will be more pronounced with an ARP build.
There’s also performance from a shorter barrel to consider. Being a handgun cartridge, 9mm Luger is literally intended to perform well from a short barrel. That cannot be said of 5.56, which performs best out of barrels 16 inches if not longer. You’ll get arguably better accuracy and performance, at least on relative terms, from 9mm.
Overpenetration should also be considered, especially if you are building a defensive platform. Shooting appropriate bullets will help, but all the same, the 5.56 is a fast, hot cartridge and there’s a risk of the bullet going too far when you shoot that. The slower, bigger bullets of 9mm are less likely to overpenetrate, especially with an appropriate load.
Also, if the size and weight of the build matter a lot to you (and they should since we’re talking about AR pistol build kits here) there are ways to make a 9mm AR build even shorter than lighter than you’d be able to pull off with 5.56. A case in point here is that there are bufferless 9mm AR uppers that completely skip the whole buffer system, making the ARP not just shorter and smaller, but lighter, too.
.300 Blackout
In the realm of AR pistol build kits, .300 Blackout, a larger alternative to 5.56, is also potentially a better choice, although for significantly different reasons from 9mm.
Now, to be clear about this, there are a lot of relative disadvantages to .300 BLK compared to both 9mm and 5.56. It is harder to find, more expensive, and produces more recoil. But there are also things it does better.
For one, and this is big for those that would build defensive platforms, the .300 BLK produces a lot more stopping power. This makes it arguably better as a chambering for home defense or as a truck gun.
Also, .300 Blackout, like 9mm, will perform much better out of a shorter barrel. Like handgun cartridges, the .300 Blackout can offer optimal performance from a barrel that’s 10 inches long, even shorter. You’ll get full powder deflagration and all the ballistic performance desired even from a short barrel.
This cartridge also responds very well to suppression, which is another selling point, on top of the fact that there are some subsonic rounds that deliver a lot of stopping power without being too loud. Plus, on top of that, subsonic .300 BLK rounds are fairly reliable, unlike some other calibers.
Why 5.56 Might Not Be the Best Choice for an ARP
In case you needed more convincing that 5.56 might not be the best choice for an AR pistol build kit, here are some things to keep in mind:
- 5.56 does not perform well from a short barrel.
- It shoots very fast and flat, and can produce a risk of overpenetration.
- It’s more expensive than 9mm (generally).
- It does not produce as much stopping power as .300 BLK.
So, ultimately, the point here is that you have options and some of them are better than the conventional standard of 5.56, especially for an ARP.
Shop AR Pistol Build Kits Here
Thinking about getting started with an AR pistol build kit? Shop our full collection and if you have any questions about parts, compatibility, or the calibers mentioned here, get in touch with us and we’ll be happy to help before you buy.