Whether by the term “short barrel 5.56” you intend an ARP or an SBR, the case remains that there are some special considerations you should take into account before building that arise from the nature of the shorter barrel.
A short barrel 5.56 will offer you superior handling and a lighter, more compact footprint that will not only prove easier to conceal, it will be easier to maneuver in tight quarters. But, that being said, you’ll be making tradeoffs.
With that in mind, here are 3 things you should be aware of before you build a short barrel 5.56.
You Won’t Get the Same Ballistic Performance
The 5.56 NATO cartridge performs best from slightly longer barrels, and the longer the barrel is, the more time the propellant charge will have to deflagrate, and the more time the bullet will have to accelerate out of the barrel.
Some cartridges perform very well from shorter barrels. The 5.56, which is very fast and flat-shooting, is not one of them. The 5.56 NATO cartridge performs best when it is fired from a barrel of 16 inches or greater.
Shorter than this, and you leave muzzle velocity on the table. The result is that you will not get the same stopping power or trajectory that you would get from a longer barrel. You will still enjoy a relatively flat-shooting bullet, but not as good as you’d get from a platform with a longer barrel.
The tradeoff is that you will get a platform that is lighter, more compact, and easier to conceal and handle in tighter spaces, so often that is worth it.
And, even so, you get more power than you’d get from most handgun cartridges, even with the loss of power incurred from choosing a shorter barrel.
But It Will Still Outperform a Handgun
It is true that most handgun cartridges will perform better from a shorter barrel, and that you will leave potential on the table when you choose a short barrel 5.56. But even so, with the loss of power you get from a shorter barrel it will still outperform common handgun cartridges like 9mm.
Let’s look at that one for an example. Depending on bullet weight and other load data, the 5.56 produces muzzle energy between 1300 and 1700 ft-lbs. Compare this to the 9mm’s 350 to 400 ft-lbs and the difference is night and day.
It is true that 5.56 will not produce quite the same figures from a shorter barrel, but it will still outperform a larger, heavier cartridge like 9mm, pretty much no matter what.
Now, that doesn’t mean that 9mm doesn’t have other advantages, just that by choosing a rifle chambering like 5.56 with your short barrel upper, over a handgun cartridge, you’ll still get better overall performance and power.
The Gun Will Likely Produce More Fouling
The last thing you should keep in mind here is that, as a result of the fact that the propellant won’t have the time it needs to fully deflagrate in the bore, the gun will produce more fouling.
This will manifest as more fouling in the bore, in the chamber, and around the action. If the platform you build has a gas impingement action, you’ll get a lot more fouling in the gas system as well.
This consideration will require you to be somewhat more fastidious about keeping the gun clean than you’d need to be with a longer barrel or an alternative chambering.
Alternative Calibers
Considering the fact that a short barrel 5.56 will not produce the same performance as a build with a longer barrel, there are some potentially better alternative calibers that will perform better from a shorter barrel.
If you’re open to a different chambering, consider:
- Pretty much any handgun cartridge (9mm, .40, and .45 will all perform well from shorter barrels).
- 7.62x39 Soviet (performs very well from shorter barrels).
- .300 BLK (a very close relative of 5.56, but performs much better from a shorter barrel).
In the latter case, the .300 BLK actually will give you the flexibility to use many of the same rifle parts in the build as the two cartridges are so closely related.
Still Here for Short Barrel 5.56 Parts?
If you’re still sold on completing a short barrel 5.56 build, take a closer look through our collection. We carry short barrel uppers, AR pistol build kits, and piecemeal parts for builds in a wide range of common and niche calibers, including those listed here.
Check out our collection and if you have any questions about ballistic performance, parts compatibility, or anything of that nature, get in touch with us and we will be more than happy to help you out.