Best 9mm AR-15 Uppers: It’s PCC Time

What’s the best cartridge for the AR platform?

Traditionalists will stand by 5.56 NATO for all time. Suppressor enthusiasts with a closet full of subsonic ammo will argue .300 Blackout is better.

Heavy hitters will squabble over 7.62 NATO/308 Win vs. 6.5 Creedmoor.

However, pistol-caliber carbines are growing in popularity because they’re cheap to shoot, fun to train with, and PCCs based on the AR-15 take advantage of the platform’s massive aftermarket support.

If you want to join in the fun, you can buy an AR-9, build one yourself, or slap a 9mm AR-15 upper on your carbine or pistol and make a quick conversion.

AR-15 upper receivers chambered for 9mm are compatible with standard AR-15 lower receivers; you’ll just need to purchase a magwell adapter to feed rounds from a pistol magazine.

Today, we are going to take a look at some of the best 9mm AR-15 uppers on the market.

How We Choose the Best 9mm AR Uppers 

Scott Murdock is a Marine Corps veteran with a background in rifles and pistol. He is a hunter, precision shooter and has completed the Vortex Edge long-range pipeline.

Extensive research was conducted based on hands-on experience and industry knowledge to create this list. As always, we update these lists often as we test out new products. So, check back regularly!

Best 9mm AR-15 Uppers

1. Faxon Firearms 16” Complete Upper Receiver

Best Full-Length Upper

Faxon Bantam 16” Complete 9mm Upper Receiver

$455

at OpticsPlanet

Prices accurate at time of writing

$455 at OpticsPlanet

Faxon (see price)

BattleHawk Armory (see price)

You might know Faxon Firearms for its quirky AR/AK hybrid, the ARAK-21, but the company makes high-end firearms chambered in everything from .22 LR to 8.6 Blackout.

The Faxon Firearms Bantam upper receiver is a solid option for anyone interested in building a high-quality 9mm PCC.

Their forged upper receiver is paired with a tapered 16-inch barrel (a 10.5-inch version is also available). It comes with a bolt carrier group, charging handle, 15-inch aluminum M-LOK handguard, and A2 flash hider.

This upper is compatible with Colt and Glock magazines.

Why use a carbine-length upper with a pistol round like 9mm? The most common answer is legality. If you’re going to use a buttstock or vertical grip, a 16-inch barrel eliminates the paperwork associated with short-barreled rifles.

Most people who want a 16-inch barrel would probably prefer that it be chambered for a rifle cartridge. That’s fair, but there are ballistic advantages to giving 9mm 16 inches of runway, namely increased velocity and reduced muzzle rise.

In fact, Ballistic Advantage reports that 9mm reaches maximum velocity with a 17-inch barrel.

What do you think of the Faxon? Rate it below!

2. CMMG Banshee Complete Upper Receiver

Best Premium Upper

CMMG Banshee Complete 9mm Upper Receiver 5″

$828

at OpticsPlanet

Prices accurate at time of writing

$828 at OpticsPlanet

CMMG (see price)

BattleHawk Armory (see price)

GrabAGun (see price)

CMMG makes some pretty awesome AR pistols, SBRs, carbines, and long-range rifles.

You can also build your own AR-9 with a CMMG Banshee upper receiver. This complete assembly includes the bolt carrier group and charging handle.

One interesting characteristic is CMMG’s Radial Delayed Blowback system. You can read the nitty-gritty details if you want, but the bottom line is that Banshee ARs don’t have the characteristic kick of the traditional blowback systems you’ll find in a lot of PCCs.

CMMG built this upper receiver to work with a range of magazines, including Glock, Colt, and Sig P320 mags. The upper receiver and handguard offer just enough Picatinny and M-LOK mounting points for something of this size.

There are a few barrel lengths available from CMMG, but I listed the 5-inch version. It’s maneuverable enough for home defense, small enough for off-body carry, and tons of fun at the range.

If you pair this high-end upper receiver with a quality, value-conscious lower like something from PSA, you’ll have a hell of a bargain on your hands. 

3. Harrington & Richardson Retro 635

Best Retro Upper

H&R Retro 635 Complete 9mm Upper Receiver 10.5″

$659

at Palmetto State Armory

Prices accurate at time of writing

$659 at Palmetto State Armory

There is no better AR-9 upper receiver for channeling 80s action movie commando raids at your local range than the Harrington & Richardson Retro 635.

This complete upper receiver keeps old-school vibes alive with a carrying handle, A2 front sight, wraparound plastic handguard, and birdcage flash hider (no forward assist, though).

The 10.5-inch barrel squeezes a little extra velocity out of the 9mm cartridge but doesn’t spoil this upper receiver’s compact size. The 1:10-twist barrel is chrome moly vanadium, and the Gen4 bolt is 8620 steel. Both get a protective nitride coating.

H&R designed the Retro 635 for use with the PSA PX-9 and Colt magazines, but the hybrid bolt will work with Glock mags, too.

It’s important to note that the carrying handle and iron sights are integral parts of this upper receiver. You can add an optic on top of them with an adapter if you want, but there’s no Picatinny rail.

There are no M-LOK slots for accessories. If you want something modern, this isn’t it. While it does have a bayonet lug, the barrel is too short to accept a bayonet. You can add a small section of Picatinny rail there for a light if you want.

4. Palmetto State Armory Gen4 9mm AR Pistol Kit

Editor's Pick

PSA Gen 4 AR-9 SBA3 Kit 4″

$499

at Palmetto State Armory

Prices accurate at time of writing

$499 at Palmetto State Armory

Starting from scratch? This PSA AR-9 pistol kit has everything but a lower receiver at a great price.

Since everything but the bare lower is included, this is a good way to dip your toes into the pool of AR builds. Everything is compatible, all the components are in the same price bracket, and you know you’ll get a quality finished product without having to research and source parts one at a time.

Nothing about this kit is fancy, but it has the essentials covered. Heavy-contour 4-inch barrel? Check. Mil-spec fire control group? You got it. Magpul grip? Of course.

You’ll also get Picatinny and M-LOK mounting points for optics and accessories. The PSA Flash Can doesn’t reduce flash or muzzle rise, but it does direct gas away from your face.

PSA’s in-house firearms have earned a solid reputation. While this kit can’t compete with premium builds, it can definitely get you up and running for a very reasonable price. The money you save will be well spent on live-fire training.

9mm Lower Receivers Vs. 9mm Conversions

Unless you’re building out a collection, why would anyone spend more money than they have to? It can be hard to justify the cost of a separate AR-9 lower receiver.

But check out our Best 9mm Lower Receivers article for our fav choices.

The truth is that dedicated 9mm lowers run better than one that’s been modified to run pistol ammunition. Spending more money will prevent cycling issues and make your AR less picky about which ammo you feed it.

Or you can also go with a magwell adapter like the Stern to dip your toes without a complete new AR lower.

Stern Defense 9mm Conversion Adapter

$179

at Brownells

Prices accurate at time of writing

$179 at Brownells

OpticsPlanet (see price)

Rainier Arms (see price)

Keep It Legal

If you do take advantage of a 9mm conversion, be mindful of which barrel you pair with which lower receiver. Installing a pistol-length barrel on a lower receiver with a buttstock makes your firearm an SBR, and that requires a tax stamp from the ATF.

The safest option is to purchase a dedicated lower receiver for each firearm to make sure pistol braces and buttstocks never cross streams.

If every barrel you own is over 16 inches, there’s no problem running all of them on one lower receiver with a buttstock. If they’re all under 16 inches, you can set up one lower receiver with a pistol brace for them to share.

Final Thoughts

Half the fun of owning an AR-15 is knowing that you can just about mix and match components like Legos to build whatever you want (as long as you do your homework).

Converting your AR-15 with a 9mm upper and a magwell adapter is a fun way to save money on training and try something new, and a dedicated 9mm AR pistol will give you a rock-solid home defense or truck gun.

There are too many great options out there to make an exhaustive list, but these are some of our favorites. Either way, your AR-15 is your canvas. Let’s see what you make with it.

What’s your favorite cartridge for the AR-15? Let us know in the comments! If you’re looking for more great AR-15 information, check out our Definitive Resource!

Latest Updates

Feb. 2024: Rewritten with all new products.