Who makes the best 9mm AR pistol?

I’m a little torn how to write this one. As a personal gun owner, I wouldn’t buy this type of build – I’d prefer to build it. However, some people aren’t comfortable doing this part.

I must say, it’s very intimidating to do. I’ve never actually built an upper receiver – I’ve added the the forward assist but that’s it! I don’t own a vise block, I’ve never added a barrel to my builds – none of it. I prefer to build the lower receivers myself and then buy the complete upper receiver.

Nonetheless – I’ll also compare AR9’s that you can buy already assembled and ready to shoot.

This isn't your mother's AR 15

What is AR9?

This AR platform can basically be described as an AR platform that shoots a 9mm round as a rifle. While there are many different pistol calibers, the 9mm is perhaps the most popular of the pistol caliber carbines. As a whole, the platform will have a platform specific upper receiver, specific lower receiver, specific barrel, specific buffer, bolt carrier group, and maybe a more rugged trigger. The rest of the gun will be milspec – the same as your AR-15 parts.

It is possible to use an AR-15 lower receiver, upper receiver, and lower parts kit to assemble a pistol caliber AR. However, the upper receiver and lower receivers in pistol caliber carbines are built specifically for this platform often have more advantages than the AR 15 platform.

9mm PCC Completed Firearm

The 9mm needs blowback to operate.

The 9mm pistol caliber carbines are built to keep the bolt to the rear when running out of ammunition and are stronger to withstand the blowback that comes with using this platform. Versus an AR 15 using a gas tube to expel the pressure.

The layman’s explanation for the pistol caliber carbines operation is that when the firing pin hits the 9mm round’s primer, the kinetic energy from the round’s blast sends the bolt back into the spring. The spring and buffer return the bolt to its normal position. The casing is ejected as the bolt moves forward anew and then loads another round.

How to build a 9mm AR: The complete AR9 Pistol

We’re not trying to make this into an end all be all instruction manual for building an 9mm AR pistol. There are better blogging tactical gear heads to consult on the subject. They have excellent DIY gun building advice to give.

However, we want you going into this with your eyes wide open. Worth Firearms carries all of these parts either locally or from the manufacturer. This means you’ll save because we’ve cut out the middleman – and sourced directly from the manufacturer.

Worth Firearm’s preferred manufacturer for AR-15 parts is Aero Precision. We’re basing our post for building an AR9 on their 9mm platform, the EPC-9.

This was the ultimate AR-9 Guide you could utilize in 2021 and beyond. It also gives us an understanding of the ballistics of the 9mm Parabellum parts : the system of buffer, twisting speed cylinder length and magazine compatibility.

The Best Handguns for Home Defense and First Time Buyers

We share these details so that you can stop getting stuck while building your newest AR9 even a suppressor-friendly one. Let’s also discuss some of the differences between AR9 and AR 15 which can help you design your own AR9 without having any pitfalls. The AR9 pistol is the same size as a AR 15 pistol and has the same functions as the AR 15.

9mm pistol caliber carbine complete parts list

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  • Lower receiver (AR9 specific)
  • Upper receiver (AR9 specific)
  • Bolt carrier group (AR9 specific)
  • Barrels (AR9 specific)
  • Buffer (AR9 specific weight)
  • AR10 buffer spring or AR9 specific specs
  • Buffer tube (any milspec tubes are fine)
  • Lower parts kits (if you build on a company’s own proprietary design, this will be mostly milspec and perhaps even a tougher trigger to endure the blowback of the pistol)
  • Handguards – ensure it’s the right length for your barrel
  • Pistol grip – pistol grips that are milspec will work
  • Stock – anything milspec will work – consider a pistol brace to stay compliant with CURRENT ATF guidelines. Check the current state and federal laws before considering such accessories.

Who makes the best AR9 lower?

All gun parts are hard to come by right now. Before entering the firearms industry as a dealer/manufacturer – I saw prices for guns and AR 9 parts at alltime lows during Trump’s administration.

However, the price for guns and parts shot up once riots and COVID-19 started. For instance, I bought a blemished M4E1 lower receiver by Aero Precision for around $75.00. Today they’re selling for around ~$100. Panic buying has certainly changed the pricing on parts and finished guns.

Colt Style Lower

While we’re big fans of the AR9, keep in mind you could also build an AR 15 to shoot a 9mm round. These aren’t the best for an AR9 build (especially since they’re not a true AR9) – we suggest using an Aero Precision EPC-9 for your build.

Glock Magazines FTW

This lower receiver is made to take 9mm and .40S&W caliber Glock magazines. I’m not saying that everyone owns a Glock and has spare Glock magazines laying around. However, I think everyone should have access to Glock mags. You can buy glock mags just about anywhere. In fact, we sell them at Worth Firearms.

Check out our Glock style magazines from Magpul and Amend2. The Glock style magazines we sell are high quality and won’t leave you wishing the lower took SIG magazines (unless you’re a SIG user of course.

Mag Release(d)

The best 9mm pistol caliber carbine upper receiver

The upper receiver should be a bit easier to find. Producers are going to make gun parts depending on what the market is. The market wants lower receivers. This supply and demand tells us that upper receivers are perhaps in abundant supply.

Aero Precision offers the EPC-9 Enhanced Upper Receiver w/ LRBHO (last round bolt hold open mechanism) for only $199.99.

Some may suggest that the AR 15 and 9mm PCC have the same upper receiver. They’re wrong. Haven’t you heard about LRBHO? Well, if you shoot an AR 15 built “AR9”, you’ll notice your bolt won’t hold open. Aero has built special features into their EPC-9 receivers that forces the last round bolt hold open feature. It’s magical.

Right upper receiver

Bolt Carrier Group

You won’t be able to use your AR 15 BCG. lt carrier group. You’ll need to purchase a new bolt carrier group due to the way the 9mm AR is designed. Because of its superior design – a few parts are unique to it. The 9mm bolt carrier group retails at $169.99 from Aero Precision and is only for use with 9mm builds.

Bolt carrier groups

What is the best barrel length for a 9mm AR?

We’re strictly talking about barrel and barrel length for the AR-9 build. Not about an AR 15 build. Worth Firearms has partnered with Ballistic Advantage and their sub-MOA guaranteed rifle barrels.

Ballistic Advantage Barrels

Ballistic Advantage sells various lengths on their website. Please be aware of state and federal laws – how they govern barrel length, stock choices, accessories, other weird laws. Your respective state laws might be more stringent than federal ones. Watch out for those as well.

Being a blowback system, these builds do not rely on the gas pressure to go through a gas port, gas block, or gas tube. As we discussed earlier, they are blowback operated. This type of gas system are perfect for a 9mm PCC.

Looking at Ballistic Advantage’s website, you can find a 16″ 9mm straight profile barrel for $155.00.

You can have a long or shorter barrel chambered in 9mm on these builds

Buffer System

You’ll need a buffer system specifically made for a blowback style AR build. The lighter buffer weight is what helps drive the bolt back into place properly. Compared to an AR 15 buffer system that has a heavier buffer and different strength spring. The buffer tube is just your typical MILSPEC buffer tube for any AR 15 build.

Lighter buffer than an AR 15

Lower parts kit

You’ll need a few stronger pieces in your lower parts kit. This is because of the blowback forces at work in an 9mm AR build’s operation. Aero Precision has hardened the trigger/hammer pins so they don’t break during the rifle’s blowback operation.


We’d highly suggest free float handguards here. Aero Precision carries them in a variety of lengths and styles. They range from $150 – $215. These go on sale from time to time so it might be smart to wait for a sale. Ensure you’re buying handguards for the right barrel length (i.e. – 15″ handguards for a 16″ barrel lengths).


There are other manufacturers out there that produce handguards, like Daniel Defense and Magpul. You cannot go wrong going name brand here but there are some lesser know brands that you might give a try as well.

Pistol grip

Many lower parts kits have a MILSPEC pistol grip in the kit. If you don’t like the one you received or if it didn’t come with one – you can purchase any MILSPEC pistol grip that you want.

Pistol grips

ATF Compliant Stock

Any MILSPEC stock will work with the buffer equipment we recommended. However, it’s important you find an ATF compliant stock for your weapon – depending on your barrel length – you may want to have a pistol brace or collapsible buttstock. Getting a collapsible buttstock with a barrel less than 16″ would make the firearm an SBR. Just bite the bullet and buy the pistol brace and apply for a tax stamp.

MAGPUL Buttstock
Pistol brace from SB Tactical


We hope you enjoyed our summary of the AR9 build and would love to hear your thoughts. We truly feel the EPC-9 from Aero Precision is the way to go here. However, Palmetto State Armory, Foxtrot Mike, and CMMG.

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