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.
THE QUICK LIST
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Best Full-Length Upper
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Best Premium Upper
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Best Retro Upper
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Editor’s Pick
Table of Contents
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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
Prices accurate at time of writing
Prices accurate at time of writing
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25% off all OAKLEY products - OAKLEY25
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Pros
- Excellent ballistics
- Ample rail space
Cons
- Longer length may be unwieldy
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
Prices accurate at time of writing
Prices accurate at time of writing
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25% off all OAKLEY products - OAKLEY25
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Pros
- Softer recoil
- Works with various mags
Cons
- Minimal rail space
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
Prices accurate at time of writing
Prices accurate at time of writing
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25% off all OAKLEY products - OAKLEY25
Copied! Visit Merchant
Pros
- Integrated sights
- Retro styling
Cons
- Adding accessories is more difficult
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
Prices accurate at time of writing
Prices accurate at time of writing
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25% off all OAKLEY products - OAKLEY25
Copied! Visit Merchant
Pros
- Affordable
- DIY friendly
Cons
- Mil-spec trigger
- Assembly required
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.
Prices accurate at time of writing
Prices accurate at time of writing
-
25% off all OAKLEY products - OAKLEY25
Copied! Visit Merchant
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.
38 Leave a Reply
Why didn't you mention the Endomag option? This is the only option that allows you to use your mil-spec AR-15 lower as is, with no magwell adapters. It has its own drawbacks, but the option exists and you can easily take your PMAG and convert it to 9mm
I like the idea of a 9mm AR style rifle or a 9mm conversion kit setup. But is anyone going to make an AR 10mm or a 10mm AR conversion setup ? Just wondering or should I say praying for. I'd love to put some Underwood monolithic copper Xtreme Penetrator Ammo down the pipe of a 16inch 10mm AR rifle.
A not knowledgeable question.
I have an ar-15. Is the referenced ar-9 different or just what an ar-15 is called when you add a complete 9mm upper? Sorry if this is so basic, but this all pretty new to me. I want to add a complete 9mm upper, but I get nervous when terms change.
I'm no expert. But I am pretty sure you need a 9mm magazine adapter for the AR15 lower, to go with the complete AR9 upper, assuming the upper comes with a matching 9mm bolt and carrier. Also a different recoil spring setup for the AR15 buffer tube. I may have left something out... again I'm no expert. Hope this helped a little.
No sir you are incorrect. There was a stay for the *Pistol Brace* rule but never stocks. Stocks on sub 16" barrels and that's an sbr and federal crime same as making a machine gun.
Great info, but what about southpaw shooters? Other than the Stag 9L that I have continued to search for, I know of no manufactures that make LH lower, receivers, or 9mm bolt carrier groupss, or
This article sucks. For the most part it deals with either glock ar9 lowers or ones for colt mags.
Focusing on a standard AR15 lower and doing a conversion is what this article should have been about. What a waist of time. Yeah I know he mentioned one adapter...BIG DEAL!!!
AR upper idea:
I'm always thinkin. But this time it keeps coming back to me. Make an AR upper that uses Glock mags on the side like a Sterling and the normal lower mag well is the ejection port. Mag release would be on the top left just like a pistol laying on its right side. The ejector on the roof of the upper and the extractor on the bottom of the bolt. A solid blowback bolt using the spring that's already in the lowers stock. Spent cases ejecting out the bottom. If need be just hang a collector bag on the bottom. With a large barrel nut covered by a front grip and being blowback operation, barrel changes would be easy. A 16in .357 Sig would smoke. Should be more simple than a .22 conversion kit. Just a polymer picatinny rail on top and you wouldn't need to furnish sights. The dependability and simplicity of an M3 Greese gun ! A .45 with a 16 1/4 inch barrel and a 26 round Glock mag. Should be very simple, light and inexpensive to produce. Should cost less to make than a Glock clone. Short barrel change for pistol lowers. Anyone with a lower could order it online and use it without worry because serials are on the lower. No FFL problems with uppers only.
I see these 16" barrels for PCC and wonder what is the effective barrel length for a 9mm round. Once all the powder is ignited every inch of the barrel is just providing drag on the round and diminishing muzzle velocity and therefore effective range. Given pistol ammo usually has faster-igniting powder to fully burn in shorter barrel lengths that are normal for pistols. I assume a 5-8" barrel is probably the sweet spot for a 9MM PCC and I would probably run it with 9mm+P ammo to leverage the effectiveness of an 7-8" barrel. If my thinking is wrong would love to understand why?
Late response, but you're not wrong. The 16" barrels are just for federal compliance with the NFA. A barrel shorter than 16" is legally a "Short Barreled Rifle" and would require additional paperwork unless you want to make a potential felony.
If you want to get a 7-8" barrel then I'd recommend getting an AR pistol.
Yes, I understand the legal issues around a 16" barrel/muzzle device length, that was not my point. My point was were you diminishing the effectiveness of the round by going with a full length barrel. From your answer, I believe we both agree, legal issues aside, going past 8" will yield diminishing returns in terms of firearm effectiveness. I have no problem using a pistol brace vs a stock so I would rather use a brace and stay at an 8" barrel length vs taking a pistol round which is already less effective than a rifle round and making it more anemic.
Article said 17" was peak performance for a 9mm.
No that can not be right. 9mm Ammo is designed to fire out of and be fully stabilized in a 4-6" barrels which means all or the majority of the powder has to ignite within that distance else it is just wasted. So assuming it ignites within 6" then the round is fighting friction of the barrel for 11 more inches with no additional power being added to the mix, so, tell me again how a 17" barrel is peak performance for a 9mm?
Another way I look at it is. I am looking at this in reverse of your view, I think. So as an example, I have some Fiocchi TMJ 40gr 1900 fps .22 WMR / Magnum ammo, part number 22FWMC 57886. I think the test barrel length they used is 16 or 18 inches for the specs. Do you think the fps is higher firing it from a rifle with 16 or 18 in barrel or my Kel-Tec PMR-30 pistol with a 4.3 inch barrel ? The way you're thinking, my pistol should have a muzzle velocity of say 2200 - 2400 fps. Because the barrel is shorter and there is less drag on the projectile through the barrel. But it doesn't, because the barrel is shorter than the test barrel they spec'd the ammo with and my pistol barrel is not long enough to get max velocity or muzzle energy out of the powder charge. Or, as usual, is my thinking backwards ? This comment is a compare and question your post and possibly learn type. Thanks for putting up with me...lol.
Thanks Mark, I think I'm on the same page now. I really didn't think about the speed and / or expansion of the powder mix, so to speak. I was more focused on the comment about the friction in the barrel part, I guess. Hey, if you get a chance to pop some 22 WMRs off from a Kel-Tec PMR30, take it or all 30 in the mag. You'll see a nice 12 in dia. by approx 14 or 16 in long muzzle fireball...it's sweet and loud.
You sound like you have a deep history with firearms. So Let me ask three more questions. 1, If manufactures made a 9mm with a different power mix, would that change it enough, of is the powder volume also a problem in the equation ? That question out of the way. 2, If powder volume is not a factor, Would it be worth it for a fairly new firearms hobbyist, to try and find a mix by reloading their own, or is it too costly and dangerous of a pain ? 3, Do you think once the PCC, in 9mm and other calibers get more popular, the major manufactures will make special PCC ammo ?
I can't tell you why, but this is from the actual article above. I'm guessing that B.A. knows how to test ammo velocity.
" In fact, Ballistic Advantage reports that 9mm reaches maximum velocity with a 17-inch barrel."
Well maybe or maybe they just want to sell more 16" 9mm barrels for people who don't want to deal with the ATF but want to shoot 9mm out of an AR platform. I mean it is fine to do that, I just would not want to be in a position where I was defending my life and that was my option to do it with.
Does anybody know the parts for the white AR9 SBR pictured? It looks similar to a CMMG but not exact so just wondering. Thank you
If you are building an AR9, the feeding of the cartridge is built into the barrel. If you are building from scratch look no further for a barrel that is guaranteed to feed from Macon Armory in Macon Georgia. If you look up their telephone number, speak with Rudy. They also have a 4" dead blow buffer that is extremely smooth and can be utilized with a carbine buffer tube and a 223 spring.
thanks for the photo of the offset scope. I think that will work. Building a 16" 9mm. Good article. Curtis
Has anyone done any research into the effect the M4 feed ramps have on reliable chambering of 9mm rounds? And if so, what bullet profile will/will not feed adequately in a PCC build? Seems to me, and I could be mistaken, that the cuts on the ramps might cause some sort of feed issues. Am I off base in this hypothesis? No one that I have read brings that into the discussion at all. Does anyone manufacture an upper that doesn't have any feed ramp cuts?
I've been heavily shopping AR parts for the last six months and there are plenty of upper receivers out there that don't have m4 feed ramps. Don't know if it matters or not.
I want to build the white and black AR SBR, where can I find the list to build one?
Who makes an AR lower specifically for M&P mags besides Nordic?
I don't know of anyone who makes a dedicated lower for M&P mags, just conversion kits like Stern.
I get the PCC idea, but struggle with "going long". I have a SIG MPX (9mm) that started as a "Pistol" (with a pistol brace) but is now a SBR (Form-1) with a solid stock, a LAW Tactical folding stock adapter, and a Mid-Evil 360 vertical foregrip. (Other cool mods as well.) I shoot it frequently with a SilencerCo Osprey can. It might be the funnest thing to shoot on the planet. What would make it "un-fun" is to lengthen it to the full 16+ and shoot it as a full-length rifle. So I just don't "get" the full-length PCC thing. But to each his own. I don't have to get it, for someone else to enjoy it.
No one cares, Rusty.....
Karri's guns sell a Fowler for 556 mags to feed 9mm through them then you dont need the adapter in a standard ar15 lower. Fowler kit is for 30 dound p mags about 40 bucks. Or the complete 9mm mag is 50 bucks
We have two AR-9 pistols, both 10.5" one full PSA and one full Angstadt, by full I mean both upper and lower receivers. Both are for Glock magazines. Have yet to shoot them, just jumping on the bandwagon.
I have recently built a Frankenstein using a PSA lower, AERO upper, CMMG 8" barrel and BCG, a no name carbon fiber foreend, an SB brace, and a CMMG PMAG conversion kit. I can still use this lower as a standard AR lower. It weighs in at around 5.5 lbs. All told, about 800 for the build. Love the AR9!
Hi Chuck,
Glad I came across your post because I'm planning on doing the same thing (AR45 though) with probably the same parts, might go with an AERO lower too since I'm an AERO fanboy. Do you need any special parts for the standard lower? Or would you recommend I go with a dedicated AR45 lower?
Also. Where did you source the no name carbon fiber handguard?
You should change the description under that picture of the white "tricked out ar pistol" which is actually an sbr because it has a foregrip on it.
Changed ;)
Suggested magwell adapters for standard lowers? Is it something that is ready to install/uninstall?
Stern Defense makes a good magwell adapter, it can be installed and uninstalled fairly easy. Comes in Glock and S&W M&P mag styles.
I have a Stern Defense 9mm 8 inch long upper and magwell adapter on a Aero Precision AR-15 lower pistol. This using the Glock magazines and I have not had any issues at all in the first 1000 rounds.