Foxtrot Mike Products Complete Upper 8.5".45 ACP for Glock Style Receivers - 8" M-LOK Rail - Blast Diffuser

Manufactured by Foxtrot Mike Products
SKU: FM45-8-5UR
MPN: FM45-8.5UR
Manufactured by Foxtrot Mike Products
8 Reviews

Out of Stock

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NOTE: This upper assembly has a barrel less than 16” in length. These uppers are intended for use in AR-15 pistols or legal short-barreled rifles. Other configurations may violate Federal law.

This Foxtrot Mike AR-15 pistol caliber carbine complete upper receiver comes with a huge assortment of features and improvements that can’t be had if you build yours from the ground up. With the FM products .45 ACP AR upper receiver, you get the functionality of a non-reciprocating side charging handle instead of the traditional T-handle. Now you can charge your SBR or pistol without coming off of your target. The upper receiver and handguard are a monolithic design with a proprietary lock system that ensures the rail won’t loosen over time. The slim free float handguard features the popular M-LOK system, so you can attach lights, rail sections, or other accessories. Underneath the 8” M-LOK handguard is an 8.5” 4150 chromoly barrel that has a 1:16 twist rate for stabilizing the .45 ACP projectile. This barrel comes with a FM products blast diffuser that eliminates the concussion to the side of your rifle for use at indoor ranges. Why build a .45 ACP AR-15 from the ground up when you can get a head start with this complete upper from Fox Trot Mike Products.


  • Non-reciprocating fixed forward charging handle
  • Left or right side charging
  • 8.5” 4150 chrome moly barrel
  • 8” monolithic free float handguard
  • M-Lok attachment points
  • Continuous picatinny top rail
  • .45 ACP bolt carrier group included
  • FM products blast diffuser with 5/8x24” threads
  • Compatible with Glock magazines

The FM products 45 caliber upper receiver is designed to be used with the FM pistol caliber lower receivers as well as other .45 Glock lower receivers that use Glock magazines. Build the ultimate pistol caliber carbine for the range or home defense with the Foxtrot Mike complete upper receiver assembly.

Feature rich, high-quality, and affordable, Foxtrot Mike Products offer cutting edge solutions utilizing the highest quality materials and manufacturing processes available.

Manufacturers Note: FM Products does not support the following items, using these may void the lifetime warranty associated with our uppers;
1) FM Products does not support Aluminum Cased ammo.  Blow backs have a much higher pressure spike in the chamber than a handgun.  Using Aluminum cased ammo in a blow back PCC is dangerous and will void the lifetime warranty of an FM Products Upper Receiver.
2) FM Products does not support import magazines besides OEM Glock magazines.  We recommend Magpul, OEM Glock and ETS magazines only.
3) FM Products does not support Spikes Glock style lower receivers.  The LRBHO requires consumers to modify the FM Products upper, to make egress for the Spikes LRBHO.  The FM Products upper is cut to the Colt spec, therefore we have no plans to deviate from that.  Modifying your FM Products Upper to accommodate a Spikes Tactical Glock style lower will void the lifetime warranty on our PCC Uppers.   
4) We only recommend Sylvan magwell adapters, as they require no modifications or adjustments to work properly.   FM Products does not support Stern Magwell Adapters as they require regular adjustments to work properly. 
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AssemblyComplete Assemblies
Barrel Length8.5
Barrel Material4150 Chrome Moly Vanadium Steel
BrandFoxtrot Mike Products
Caliber Gauge.45 ACP
Gas System LengthBlowback
Gas System TypeBlowback
Handguard8 in M-LOK Rail
Muzzle DeviceFM Blast Diffuser
Twist Rate1:10

WARNING: This Product can expose you to chemicals which is known to state of California to cause Cancer and Reproductive Harm. For more information, see

Looks and functions excellent! Do not like charging handle.

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I like the upper's looks. I paired it with a New Frontier Armory lower. The upper & lower look and function good together except New Frontier's LRBHO is in their uppers, not lowers so that function does not work with this combo. It feeds well even JHP rounds. I put a shorter muzzle device and took about 2 inches off total length. However, I like the looks of original Blast Diffuser better and may change back. I gave it a 4/5 because the little plastic side charging handle is very uncomfortable without very thick gloves.

AR.45acp side forward charging handle

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l agree with Terry's comment regarding the difficulty using the charging handle without gloves, it is not user friendly due to its size and design, hopefully somebody will come up with a replacement soon. Otherwise would 've gotten the 5 stars.

Love mine! Shooting sub sonic is a real joy, incredibly accurate too!


Love mine! I love mine and shooting subsonic is a joy, best quality pcc on the market, cant geat the price! I contacted FM, the new charging handle is why they are pricved the way they are. They offer a paratrooper style to anyone who wants them.

Lightweight and Handy

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Works great, I built my own charging handle. Very cool.

Mine won't run.

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I want to like mine but it won't run more than two or three shots without a jam with any of the three new Glock mags that I tried. I used a Spartan lower and a .45 buffer and spring kit and Stoner parts kit and an SB3 brace. It looks great but it won't run. I'm sure FM will help me get it right.

It runs!

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Well I ended up sending my upper back to FM Products and they went to the extent of buying the same receiver to I have to make sure it would run on mine. They ramped the barrel and beveled the edge of the chamber and now it runs like a top! I tried several brands of ball ammo along with my cast RN's and SWC's and it would even chamber an empty case most of the time. I hope they start ramping all of their barrels as it makes a world of difference. Their customer service was great also.

Barrel threading listed WRONG!!

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Barrel is NOT threaded 1/2"-36 it's 5/8-24. Found out after I spent $40 on a new muzzle brake. Primary lists it as 1/2-36 as FM does..contacted FM, never even had a response..Their web site still lists the does Primary Arms....Still trying to sell this useless muzzle brake...
<br>From PA: I'm sorryfor the bad copy. We've updated the page. If you purchased your muzzle device from us, we'll be happy to accept a return.

Needed work out of the box, but ended being great.

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<br>-side charging handle is very smooth.
<br>-After the issues were corrected (below) it runs like a top!
<br>-No dust cover for the breach.
<br>-The trapdoor is made of plastic and seems a bit flimsy.
<br>-no room for a front BUIS. This can be overcome, however.
<br>-The screws that connected the handrail to the upper receiver were not properly seated and were very crooked.
<br>-The barrel was off centered, and appeared to be bent about 2/10ths of a cm to one side.
<br>-CHECK THE FRONT OF THE BOLT CARRIER GROUP! If it has lip at the bottom of the bolt face that juts out about 4/10th of a cm your weapon will probably have feeding issues.
<br>NOTE: I contacted FM directly, sent them photos of all of the issues listed in the CONS. They advised that the upper should not have been shipped like that, and apologized for the issues. They fixed EVERYTHING, at no cost to me, and even had everything put on rushed delivery. The customer service of FM and Primary Arms have been fantastic!