How to Build Your Own 9mm AR Pistol

How to Build Your Own 9mm AR Pistol

How to Build Your Own 9mm AR Pistol

Thanks to the modularity of the AR platform, people have come up with ways to adapt the components to make firearms in a wide variety of different calibers.

Different rifle calibers were the first to be adapted to the platform, but now pistol calibers have entered the mix and they’ve proven to be exceptionally popular. There’s just something that’s a bunch of fun shooting pistol caliber cartridges from the AR platform.

If that sounds like fun to you, too, then you might want to build your own 9mm AR pistol. Let’s take a look at what all that entails.

What is an AR9?

Unlike the nomenclature of the AR-15, the numerical part of the model designation of an AR9 refers to its caliber: 9mm. So, quite simply, an AR9 is a firearm that is patterned after the AR platform but built for the 9mm cartridge.

How is an AR9 a Pistol?

An AR9 is legally classified as a pistol in the same way that rifle-caliber AR platform firearms can be classified as a pistol. AR9 pistols have barrels shorter than 16″ and are not equipped with a buttstock. Instead, they are equipped with a brace.

AR9 vs AR-15

While visually similar, the AR9 and the AR-15 are two different firearms for different purposes.

An AR9 is great if you’re looking for a firearm that offers caliber and magazine compatibility with your EDC handgun. Most people’s carry guns are chambered for 9mm, and AR9s are usually set up to use Glock mags, which can be found pretty much everywhere. An AR9 is also a great option for something like home defense or a truck gun.

While an AR-15 can also be used for home defense or as a truck gun, it has the benefit of shooting a rifle caliber cartridge, thereby extending the range of the firearm.

They’re both great choices; the ultimate decision is up to you and will be based on exactly how you plan to use the gun.

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Building an AR9

Alright, let’s get down to building an AR9. First, you’ve got to make some parts decisions. Once you have those squared away, it’ll be time to put the pieces together.

Find the Best Barrel Length

Since this is going to be a pistol, your barrel length will be somewhere under 16″. Of course, you don’t want to go as short as, say, 5″ because then you might as well just use a more traditional pistol. Two very popular options are 7.5″ and 10.5″ since they give you the extra barrel length without being too long and defeating the purpose of the build.

Choose Your Mag Type

As was mentioned above, most AR9s use Glock mags, but you can also get ones that are compatible with a variety of other types, such as Colt, S&W’s M&P, and even modified Uzi mags.

Choose a Lower to Use

You can opt for a purpose-built AR9 lower that will only accept pistol caliber magazines, or you can buy an adapter that will allow a standard AR-15 lower to accept these smaller magazines. It all depends on whether or not you want a dedicated AR9 or an AR-15 that you can adapt to work with AR9 parts.

Find the Right Buffer

There are different weight buffers for different types of AR-pattern firearms, and they can vary based on the caliber of the firearm, the length of the barrel, and the length of the gas system. Make sure you’re using the right one!

Using the Proper Bolt Carrier Group for Your Lower

Just like the buffer, your bolt carrier group for an AR9 will be different than the one you would use for an AR-15. Pay attention to which one you pick out!

Pay Attention to Your Muzzle Device Threading

Whether you’re going to be using a flash hider, compensator, muzzle brake, or a suppressor, it’s important to know both the threads on the end of your barrel and on your muzzle device. If the two don’t match, then the best you can hope for is to use an adapter. At the worst, you’ll have to have the barrel rethreaded or choose a different muzzle device.

Upgrade Your Trigger and Hammer Pins

You can certainly use the “milspec” parts that come in most lower parts kits, but people tend to swap out their trigger and hammer components for a better feel and better trigger pull. Now would be the time to consider that.

Pick Out a Brace

The options for braces and other stabilizing devices are seemingly endless. The market is pretty well saturated with different types and configurations, so just pick one that best suits your personal needs – or just pick one that you think looks cool. It’s totally up to you and the brace or stabilizer can be easily swapped out later.

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Assembling the Rest of Your AR9

Now that you’ve got all of your parts together, it’s time to assemble your AR9!

Grease the Outside Rim of the Barrel

A little bit of grease goes a long way to ensuring smooth assembly and longevity.

Insert Barrel into Upper Receiver

Slide your barrel into the upper receiver and make sure everything lines up and that your threads are free of any obstructions that would prevent proper attachment and seating.

Attach Barrel Nut over the Barrel

The barrel nut is essential to keeping your barrel securely attached to your upper receiver. Proper installation and tightening is essential.

Unpin the Upper and Lower Receivers

At this point, you can take your upper and lower receivers apart and set the lower receiver aside.

Insert Upper Receiver into a Vice Block

This will help hold your upper steady and ensure that nothing gets crushed or damaged.

Install Muzzle Device onto the Barrel

Whether you choose a flash hider, compensator, muzzle brake, or a suppressor is up to you – though we’re kind of partial to suppressors!

Slide Handguard over the Barrel & Tighten

It’s time to get a grip! Install your chosen handguard over the barrel and make sure that it is securely attached at both the front and rear of the barrel.

Insert the Bolt

Now’s the time to insert your bolt carrier group into the completed upper receiver.

Re-Pin the Lower Receiver to the Upper

The final step is to pin your upper and lower receivers together again and ensure that they function properly with one another through some manual cycling and then dry-firing before attempting any live fire on the range.

Build Your Own 9mm AR Pistol

There’s no denying how fun it is to shoot a 9mm AR pistol, and it’s even more fun and rewarding to shoot one that you picked out each and every part for and assembled it yourself!

The only possible way to make this experience any better is to go shooting with your new AR9 and a suppressor. Luckily, Silencer Central can walk you through the entire suppressor selection, purchase, and delivery process right from the comfort of your own home!

Get started today on building your own AR9 and purchasing a suppressor!


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