Troy Defense M5 9mm Carbine being shot

7 Best AR 9 Lowers

We may earn a commission when you purchase through the links on our site. Find out more here.

The AR-15 can do a lot with just the change of an upper, but sometimes to get the best out of it — you need to just get a new lower.

A dedicated AR-9 build is just one case since a new lower will give you a better form factor for all kinds of pistol caliber shenanigans.

From the high-end to the budget-friendly, we’ve got the best ar-9 lowers here for you!

BONUS OFFER: Get your free shooting range targets to print at home!

Get your free targets to print at home!

Subscribe to our newsletter and get gun deals, educational content, hand's on reviews and news on law changes!

What Makes An AR-9 Different From A Standard AR-15 Lower

Mostly the magazine and feed ramps. You can’t fit 9mm cartridges in a 5.56 NATO magazine so you need to convert the rifle to something else — like Glock magazines.

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.

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

And last but not least, the magazine release is changed to accommodate the new magazine.

Looked at individually these are small changes, but collectively they make a lower that is wildly different from a standard AR-15. And yet, they feel basically the same.

Glock or Colt Magazines? (Or Beretta, Sig Sauer…)

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.

Argentine soldier armed with Colt 9mm SMG
“Argentine soldier armed with Colt 9mm SMG — very slick”

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 much 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.

The 7 Best AR-9 Lowers

1. 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!

Aero Precision EPC-9

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.

3. Rainier Arms Billet Receiver Set

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.

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

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.

It’s expensive, but you get what you pay for.

4. KE Arms KP-9

Okay, technically this isn’t on the market… yet.KE Arms recently released the KP-15 monolithic polymer lower and it is amazing.

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

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

KE Arms is now working on bringing us the exact same lower but now in 9mm and using Glock magazines!

We’re crazy excited for this and expect it to be as great as the KP-15 is. But it’s hard to tell for sure yet.

Once it’s released, we’ll update with a full review on it!

Best Colt (and others) Lowers

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, not a bad price 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.

Wrapping Up

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!

You might also enjoy reading

Total
19
Shares
Leave a Reply

Your email address will not be published. Required fields are marked *

Related Posts
6.5 Creedmoor AR-10 Build
Read More

Best 6.5 Creedmoor Uppers

Are you looking to put together your own 6.5 Creedmoor AR-10? If so, you’ve come to the right place. That’s because if you want to build a 6.5 Creedmoor AR-10, but already own an AR-10 chambered in 7.62x51mm NATO or .308 Winchester (the most popular AR-10 chambering), then all you should theoretically need is just ... Read more
Budget 1911 Header
Read More

Best Budget 1911s Around $500

In this Article: Three Price TiersPersonal Experience With Budget 1911sTypes Of 1911sThe SpecsRock Island Armory 1911ATI 1911Cimarron 1911American Classic IITaylor’s & Co. Full-Size A1 1911Taurus PT1911Ruger SR 1911 Standard I am a retired public school music teacher. I also have an affinity for a good 1911 – I’ve owned several. But, when you combine these ... Read more
A close up shot of the Ruger P95
Read More

The 4 Best Ruger P95 Holsters

At first glance, you may not think there’s anything too special about the Ruger P95. It certainly isn’t one of the sleekest looking pistols on the market. While it may not be considered “bulky”, it may not have the most ergonomic feel to it either. It can be a little tricky to find the right ... Read more

Talk to me

Hi! I'm Mike, one of the oldest writer of Sniper Country! If you have any feedback or question about my articles, please submit it here, it's always appreciated!

[contact-form-7 404 "Not Found"]

Claim your targets for free (worth $99)!

Join 212,000 avid gun enthusiasts and claim your print-at-home shooting drills. Receive exclusive gun deals once a week and all our great reviews right in your inbox.