1. Home

Foxtrot Mike Products Hybrid Polymer FM9 Complete AR9 Lower Receiver

Manufactured by Foxtrot Mike Products
Manufactured by Foxtrot Mike Products
11 Reviews

In Stock

Orders of non-FFL items will ship same day if ordered before 3:30pm CST (M-F). FFL orders will ship within 5 business days if transfer details are provided.

For individual Officer, First Responder, and Military pricing please make sure you are logged in. for details

Items that are regulated by the ATF have restrictions and requirements: 
•Your entire order will ship only to a Federal-Firearm License holder.
•Please contact your local FFL prior to placing your order to ensure they are still accepting transfers.
•A copy of your order/invoice as well as the current FFL license for your local dealer must be emailed to ffl@primaryarms.com.



This Foxtrot Mike Products AR9 lower receiver features a hybrid polymer design combining the light weight of polymer and the durability of aluminum. It features aluminum inserts in all the high stress areas to prevent breakage allowing it to last thousands of rounds. It features a last round bolt hold open and completely ambidextrous controls. It comes fully assembled with a trigger, mag release and bolt release buttons and features an integral pistol grip. Build your Glock magazine compatible AR9 pistol caliber carbine today.


  • Made from polymer with aluminum inserts
  • Gives you the support needed to go with 9mm Glock style magazines
  • It has a last round bolt hold open
  • Ambidextrous safety and mag release
  • Comes with a lifetime warranty
  • Made in the USA

An American made product, the Foxtrot Mike Products Hybrid Polymer FM9 complete lower receiver comes with a lifetime warranty that will guarantee you quality performance for years to come.

See More


BrandFoxtrot Mike Products
Caliber Marking9mm Luger
FinishHardcoat Anodized
Receiver MaterialPolymer
Trigger Pin DiameterMIL-SPEC .154
California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to www.P65Warnings.ca.gov.

Ratings & Reviews

11 reviews


Solid Low Cost 9mm Lower With Some Upgrades


I bought the FM-MkII 9mm solely for the low cost. I mated this with the Foxtrot Mike 5” upper. First 100 rounds were flawless. Unique features that I was not expecting: pistol grip is molded into the lower so you are stuck with it. However stippling is aggressive and grip is very ergonomic. Grip will fit an extra magazine in it and has a mag release. I’ve never seen this feature before in an AR platform. Selector switch is ambi and 45 degrees. Rear takedown pin requires some help to release because the end of the pin sits flush. This is the one that caught me - Bolt release is ambi, but requires a notch to be cut in the upper. Of course my Foxtrot Mike 9mm upper had no notch, so LRBHO did not work on my first trip to the range. However there are instructions provided with the lower showing how to replace the ambi rod with a second set screw that allows the bolt catch to work without having to modify your upper. Overall great product for the cost.

Ambi bolt release requires modification


This is highly textured. It feels like it is 50 grit sandpaper; that's not a complaint.
However, the ambi bolt release (right side) requires the owner to cut a small notch into the upper to function. So, the LRBHO won't function until you remove the ambi bolt release which was simple with a 1/16 allen wrench (not supplied). A link to an instructional video on how to modify your upper is included.

I'll likely end up modifying the upper so ambi bolt release will function. Who doesn't enjoy modifying their firearms?

I still recommend buying the Hybrid Lower.

Ambi bolt requires modification of the upper

by -

The grip feels like 50 grit sandpaper. That's not a complaint.

The ambi bolt release requires the owner to modify the upper, by cutting a notch into it, for the LRBHO to function. Otherwise, the ambi bolt release can simply be removed with a 1/16 allen wrench (not included). Once removed the LRBHO will function. A video link on how to modify the upper in noted in the instructions.

I would recommend anyone to buy it.


by -

I have several 9mm ARs. My Angst build is by far my favorite. Even my drop in kit version. I was excited about the FM-9 so I purchased both the assembled lower then upper when available. Making them fit was a bit of a bear. The two FM products act like they just don't to join without some heavy persuading. Over I love the feel and it shoots ok. Maybe for a pinker it will do. I do have other FM products that are awesome, this poly one piece is "ok"

Feels great!


Man this lower fits very tightly with the foxtrot Mike 7 inch 9mm upper. You will have to attach and detach it a few times to loosen it a tad. The trigger has ever so little creep before a nice crisp break. The secondary magazine slot in the grip is convenient but the mag release for it on mine is extremely stiff. I would recommend ejecting some loaded mags around the house to loosen it up. Speaking of the grip, it is nice and stippled and very comfortable in my hand. I would definitely recommend this to anyone that is interested.

Great lower

by -

This is the 4th Foxtrot Mike lower. Love the feel and operation


by -

Great fit and finish. Thanks,
Tommy 4th FM lower

No issues AT ALL!

by -

Spit 300 rounds of mixed 9's through it, no malfunctions at all. And yes I bought the upper that goes with it. LRBHO worked like a charm!
I'm going to buy another one just like for my son on his birthday..

Top tier budget Ar-9


This lower hasn't disappointed yet Countless round have gone thru it without malfunctions. Paired with the Foxtrot 5 inch upper without modification. Definitely pull the trigger if you want a great quality Ar-9.

Great lower but be careful what upper you buy!!

by -

Great lower. Cool features but buyer beware that IF YOU PLAN TO USE EVER PURCHASE A SUPPRESSOR THAT YOU DO NOT BUY A FOXTROT MIKE UPPER. Reason being is that the muzzle threads on FM 9mm uppers are not MILSPEC and therefore will not accommodate the 1/2" x 28 threads on most every 9mm suppressor made in the U.S. The threads on a Foxtrot Mike barrel are 1/2" x 36 and so far I have not found any suppressor company that sells an adaptor. Costly endeavor for sure. Now have a suppressor that cannot be used on the FM9 upper.
Otherwise a great product.

Note: It was good to speak to you on this and provide a source for an adapter that may work for you. Please let us know if there is anything else we may help you with.