Troy Defense M5 9mm Carbine being shot

Best 9mm AR Lowers to Complete Your AR-9 Build [Buying Guide]

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It takes finesse and adjustment to use a pistol cartridge in a rifle. Building a 9mm AR requires careful consideration of the lower receiver to ensure reliable magazine feeding. If you’re interested in making a 9mm AR carbine, you should start with the best 9mm AR lowers you can find for your AR pistol caliber carbine or pistol-type handgun.

Changing the upper on an AR-15 can improve its capabilities, but sometimes a new lower is all that’s needed to make the gun truly sing. At the same time, a growing number of gun owners are upgrading, converting, or custom-building their own ARs. It’s not hard to assemble a 9mm AR carbine, either. You may also feed them Glock magazines, which are inexpensive and plentiful.

Luckily, I’ve got you covered, and I’m always happy to lend a hand. Throughout the years, I’ve shot hundreds of 9mm lowers, and the ones on this list are among our favorites. Okay, so let’s get going.

Best 9mm AR Lowers Summary Table

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Difference of an AR-9 vs. Standard AR-15 Lower

Aero Precision EPC-9 great rifle
Aero Precision EPC-9 is a great rifle — or in this case, SBR.

The magazine and feed ramps are the main distinguishing features of the AR-9 compared to a conventional AR-15 lower. You’ll need to swap out the rifle’s magazine for something like a Glock’s because 9mm rounds won’t fit in a 5.56 NATO magazine.

Most AR-9s also handle ejection via a part integrated into the lower, and the same goes for any Last Round Bolt Hold Open feature. And last but not least, the magazine release was altered so that it would be compatible with the new magazine.

Although each of these modifications is quite minor on its own, when combined, they create a lower that is very different from a typical AR-15. However, they feel similar.

What Magazines Should You Use?

Argentine soldier armed with Colt 9mm SMG
Argentine soldier armed with Colt 9mm SMG — very slick.

The first decision you should make is what kind of magazine system you want to use.

Generally speaking, I strongly recommend Glock.

While Colt SMG magazines were the original and classic choice, they are much harder to find, give you fewer options, and are expensive to replace. However, they are double-stack and are easier to load.

More niche platforms like Beretta 92FS or Sig Sauer P320 magazines are really cool but almost impossible to find a dedicated lower for. Magazine well conversion kits are great, but they aren’t a complete lower.

Glock offers a number of advantages and basically no disadvantages. The magazines are crazy easy to find and high-quality options are on the market from Glock, Magpul, ProMag, and more.

They also come in as little as 10 rounds and as many as 50-round drums. Plus, they’re fairly inexpensive. More mags, more shooting, more fun.

Lowers With Triggers

Most of these lower is stripped, but some do offer completed options for you to consider. Something you should keep in mind about AR-9 triggers though is that they take much more of a beating during the firing process than a normal AR-15 trigger.

Due to the blow-back operating system of an AR-9, this imparts a lot of shock into the trigger.

A standard mil-spec trigger simply isn’t strong enough to handle it long-term.

In recent years a number of brands have started to offer 9mm or PCC triggers that are designed for the extra trauma induced by the AR-9 system.

CMC, Timiney, and Wilson Combat are just a few that offer these now.

Buyer’s Guide to the Best 9mm AR Lowers

Before buying an AR lower, here are some things to consider.

Durability

Forged aluminum of aircraft-grade 7075 is one of the best options for the material you should look for. Aluminum is also a great material since it is both lightweight and strong. The Beretta 92FS and other metal-framed handguns use aluminum frames for the same reasons.

Magazine Compatibility

There are two main categories of AR9s, depending on whether they use 9mm magazines designed for the Glock or the Colt SMG. Consider the magazines you intend to use before choosing a lower receiver.

There is no functional difference between magazines designed for the Colt and the Glock. However, Glock magazines are more accessible, affordable, and customizable. Keep in mind that not all AR9 lower receivers are compatible with all aftermarket Glock mags.

Finish

Make sure the receiver has a rust- and corrosion-resistant coating in addition to being sturdy. A rust-resistant treatment is essential if your lower is ever going to be exposed to wet conditions like rain, snow, or humidity.

A hard coat anodized finish is a great option if you’re looking for something that won’t corrode. Parkerizing, stainless steel, nickel boron, and coatings like Cerakote and Duracoat are a few more options.

The 9 Best AR-9 Lowers

1. Aero Precision EPC-9

Aero Precision EPC-9

One of the newest options on the market, Aero Precision has a long history of making great AR-15 lowers, rifles, and pistols. And now they offer 9mm options and will soon be offering 40 S&W, 10mm, and more.

The EPC-9 is a forward-thinking pistol lower designed for Glock magazines and optimized for long-term use.

These are budget-friendly lowers that pack in a lot of features like last round bolt hold open and enhanced parts to withstand the blowback action.

The design and styling closely match Aero’s normal lower also and include a fully forged trigger guard and flared magazine well for easier loading!

Available in Black, FDE, and OD Green — these are selling out constantly, so you might want to sign up for the Aero mailing list.

2. Palmetto State Armory PX-9

Really, there isn’t anything super special about the PX-9. It’s a functional AR-9 that gives you what you need without any added bloat.

What I like about it is that it is cheap. If you’re not sure about the 9mm PCC platform or just need a gun to treat it like an old truck, this is a perfect lower for you.

Build PX-9 braced pistol
“If you want a really small and lightweight package, buy or build your PX-9 as a braced pistol!

Sadly, it doesn’t have a last-round bolt hold open and it doesn’t take just any AR-15 upper — it must be used with a Palmetto State Armory Hybrid 9mm upper.

Thankfully, those uppers are a great price and are surprisingly solid units.

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3. Rainier Arms Billet Receiver Set

Rainier Arms Billet Receiver Set
“Rainier Arms Billet Receiver Set via @AR15News on Twitter

Not only is this one of the prettiest 9mm lowers ever made, but it also comes packed with features. Lots of AR-15 lowers these days are ambidextrous, but very few AR-9 lowers are.

Rainier Arms gives us a complete ambi lower with a bolt release and magazine release on both sides of the firearm.

You also get a flared magwell for easy reloads, last round bolt hold open, and is compatible with short-throw safety levers.

And best of all — you can build this to be 9mm, .40 S&W, or .357 Sig. The lower can accommodate any Glock magazine in those 3 calibers.

Also, it’s expensive, but you get what you pay for.

4. KE Arms KP-9

The KE Arms KP-9 in pre-production testing
“The KE Arms KP-9 in pre-production testing. Image via u/SinistralRifleman on Reddit

KE Arms recently released the KP-15 monolithic polymer lower and it is amazing.

Super lightweight, unbeatable, strong, and highly ergonomic, the KP-15 is a great lower in every possible way.

The KP-9 is an AR15-style receiver designed to accommodate 9mm Glock magazines. It is manufactured of injection-molded 30% glass-filled nylon and features a buttstock, buffer tube, pistol grip, and trigger guard that are all integrated parts of the receiver.

It works with common 9mm AR15 lowers and lower parts kits. Also, it has a “Winter” trigger guard that allows you to shoot while wearing gloves, and a better grip for ergonomic usage.

5. Palmetto State Armory Colt-Style AR-9

Just like the PX-9, this is a functional lower. Really, there just isn’t any difference between the normal PX-9 and this except in what magazine you use to feed it.

It’s simple, it works, and it’s affordable.

6. Spike’s Tactical Colt-Style 9mm Lower

Another option that really doesn’t have anything to show off, Spike’s is a solid unit that has a bit better fit and finish than the cheaper PX-9 does.

It is still a simplistic design though and doesn’t offer anything ambi or a last round bolt hold open, but it does at least have a fully formed trigger guard.

A solid option that will serve you well.

7. Stern Defense MAG-AD9

Yes, technically, this isn’t a lower but it’s close enough.

Stern Defense’s magazine conversion is a great way to use your current AR-15 lower and just change what magazine it takes. Throw on a 9mm upper and you’re good to go.

It’s easy to install, affordable, and lets you choose from a much larger host of magazines than just Glock and Colt.

Beretta 92FS, Sig Sauer P320, .45 ACP Smith & Wesson M&P, or S&W M&P 9mm mags — with this many options, it’s almost guaranteed you can find a magazine conversion for mags that you already have.

This was where I first started in the world of pistol caliber carbines and I loved it.

8. Angstadt Arms 0940 Lower Receiver

Another excellent stripped lower, the Angstadt Arms 0940 AR-15 Lower Receiver is a fantastic option. With its flared magwell, it is compatible with Glock magazines.

This 0940 Lower Receiver from Angstadt Arms is made from 7075-T6 billet aluminum and has a hard-coat anodized matte black finish. It is compatible with any upper receiver meeting the requirements of the Mil-Spec standard.

It is compatible with 9mm, .40 S&W, and.357 SIG cartridges, making it useful for a wide variety of PCC designs. It is compatible with Glock 9mm double-stack magazines, but only aftermarket versions.

There is also a large trigger guard, a threaded bolt catch screw, and a last-round bolt hold open. It’s compatible with the AR-15 hammer and normal AR upper receivers, and 9mm bolt carrier assemblies.

9. Foxtrot Mike Products FM-9 Billet Lower Receiver

FoxTrot Mike Products AR-15 FM-9 Billet Stripped Lower Receiver may be modified right out of the box. Thanks to its mil-spec design, it may be used with any standard AR9 component.

The FoxTrot is a Glock magazine-accepting handgun constructed from aircraft-grade aluminum and incorporates a last-round bolt hold-open mechanism. This is a great upgrade that’s not included with all AR9 lower receivers.

The stripped receiver already has a magazine release and a bolt release attached to it.  The lower components set contains a GI Trigger Group, a.308 carbine recoil spring, a 6.5-ounce heavy buffer, and a mil-spec 6-position carbine buffer tube.

Unfortunately, this lower has no stock. As an additional note, please be aware that this receiver is not legal in California.

Wrapping Up: Best 9mm AR Lowers

Be it a magazine conversion for a Sig Sauer P320 or a high-end Glock magazine builds to match your G34 race gun — the pistol caliber AR platform is here to stay.

An idea popular since the 1960s, we live in a golden age for firearms and this is just one of many examples.

Personally, I strongly recommend starting with a Stern Defense MAG-AD9 if you’re not sure what to get. 

If you want to jump in with both feet, the Aero Precision EPC-9 is pretty awesome and for sure the best bang for your buck!

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