While many ARs are chambered in 5.56 or .223, or at least in some other common rifle caliber like 7.62 or 6.5, there are other options at your disposal. Some of these are handgun calibers, and among the best of these are 9mm AR uppers.
Here are some of the best reasons to choose just that for your next build.
High Ammo Availability
If you go into a gun shop, you can pretty much bet that they’re going to have, at minimum, three types of ammo. These are .22LR, 12 gauge target loads, and 9mm FMJ. Even during the height of the ammo crisis, you could get 9mm pretty much anywhere, albeit at a much elevated price.
Sporting Uses
The 9mm also has a lot of sporting uses, ranging from plinking and high-volume target shooting to training, drilling, and all different types of shooting competition. Also, where legal, 9mm can be used for handgun hunting of certain game.
Defensive Uses
If you build a platform with a 9mm AR upper, you may also be able to use that platform for defensive applications as a truck gun or a home defense PDW. It offers solid stopping power with an appropriate round and produces less recoil than alternatives like .45 ACP or 10mm Auto.
Low Recoil
Another of the great selling points of a 9mm AR upper is that 9mm Luger produces comparatively little recoil, certainly less than any rifle cartridge that would be used to build an AR. This makes 9mm a great option for building a platform for smaller-framed or lighter shooters, or for beginners.
Low Cost
The 9mm Luger is a relatively inexpensive cartridge. Not quite as cheap as .22, but definitely comparable to 5.56 and .223, and like those latter two cartridges, you can get it in bulk or buy surplus, or police trade-in, and get an even better deal. This affordability makes it one of the best cartridges for high-volume target shooting of all disciplines, period.
The Build Will Be Lighter and Potentially More Compact
If you’re looking into the potential for building an ARP or a PDW, generally, 9mm AR uppers are shorter and lighter than their rifle counterparts. Though this is not always the case, if your goal is to build something small and light, a lighter caliber is a better option and that makes a handgun cartridge a solid bet here.
Better Performance from a Shorter Barrel
It is also the case that you will get better performance from a handgun cartridge from a shorter barrel than you will get from a rifle cartridge, all else being equal. This makes 9mm a solid option for building an ARP, a PDW, or just a PCC. High-velocity cartridges like .223 can be fired from short barrels but they will produce a lot of fouling and simply will not perform as well as they would from longer barrels. The same is not the case for 9mm which will perform admirably from a much shorter barrel.
Lower Risk of Overpentration
Loaded with an appropriate bullet, a cartridge like 9mm produces a far lower risk of overpenetration than faster rounds like .223. Also, other rifle cartridges, which are faster and which produce much more stopping power, are much more likely to overpenetrate. With responsible handling, good shot placement and a hollow point bullet, that is much less likely with 9mm.
Better Expandability Than a Handgun
At this point you might be thinking, if you’re going to build a really compact platform chambered in 9mm, why not just get a handgun, since they are much more affordable as a general rule, not to mention the fact that they are lighter and easier-handling.
Well, with an ARP or PDW, you are likely to have many more opportunities to expand the platform because there will be more attachment points. That is definitely the case for most ARPs, which have quad rails, which, although short, are much more accommodating than the few (if any) attachment points that are present on most handguns.
Bufferless Options Are Available
Lastly, if you are trying to build an ARP, and want to make it as compact as possible, with a 9mm AR upper you will have the option to build bufferless, which will let you make the platform as compact as possible. This would not be practical with other cartridges that generate higher chamber pressures, like .223 and 5.56. They’re good with roller-delayed blowback but not direct blowback. However, you can build with a 9mm AR upper using direct blowback, which will let you forgo the buffer system entirely.
Start Your Next Build with a 9mm AR Upper
Ready to start your next AR build? Consider building with a 9mm AR upper and enjoy the benefits mentioned here among others. It might be your favorite AR chambering yet.