Radical Firearms 7.5" 5.56 NATO 1:7 Pistol Length M4 Barreled Upper - 7" M-LOK FCR Gen3 Rail

Manufactured by Radical Firearms
SKU: FU7.5-5.56M4-7FCR3
MPN: FU7.5-5.56M4-7FCR
Manufactured by Radical Firearms
3 Reviews

Out of Stock

NOTE: Limit 1 per household. Quantities exceeding 1 will not allow checkout.



The Radical Firearms 7.5" 5.56 NATO M4 Barreled Upper Receiver is a law enforcement grade, drop-in solution for your next AR build. Crafted with quality materials and covered by Radical’s lifetime warranty, this MIL-SPEC upper receiver provides an outstanding solution for any budget. Arrives at your door with the hard work done. Complete this build with your favorite lower receiver, bolt carrier group, charging handle, and sights, then head for the range!

The Radical Firearms FCR system is a slim handguard that provides the weight savings you want without sacrificing any of the mounting possibilities you require. This freefloat design offers a monolithic Picatinny rail and plenty of M-LOK attachment points for all your gear.

NOTE: This upper receiver has a barrel that is less than 16” in length and is intended for use in AR pistol or legal short-barreled rifle builds. Other configurations may violate Federal law.

Does not include bolt carrier group or charging handle.

  • 7.5" 41V50 chrome moly vanadium steel M4 contour barrel
  • Chambered in 5.56 NATO with a 1:7 twist rate
  • 1/2x28 A2 flash hider
  • 7" Radical Firearms M-LOK FCR rail
  • Gen 3 rail mounting system
  • Made in the U.S.A. in Stafford, Texas!
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AssemblyBarreled Assemblies
Barrel CoatingSalt Bath Nitride
Barrel ContourM4
Barrel Length7.5
Barrel LiningSalt Bath Nitride
Barrel Material41V50 Chrome Moly Vanadium Steel
BrandRadical Firearms
Caliber Gauge5.56 NATO
Gas System LengthPistol
Gas System TypeDirect Impingement
Handguard7 in Radical M-LOK FCR Rail
Muzzle DeviceA2 Flash Hider
Thread Pattern1/2 X 28
Twist Rate1:7

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 www.p65warnings.ca.gov

Ratings & Reviews

3 reviews

  • 4 stars
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  • 2 stars
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Highly recommended


500 rounds, no malfunctions. Running a PSA M16 C-158 BCG and Spike’s H2 buffer. No complaints. Couldn’t be happier.

Absolute Steal. Functions Flawlessly


This thing runs flawlessly. 1,500 rounds and no malfunctions using an Anderson pistol lower with and Anderson LPK. As far as aesthetics go I would give the finish an 8.5/10. This makes a very high functioning and low cost AR pistol.

Mine was dimensionally out of spec. - buy a higher quality brand.


First Radical Firearms upper I have bought and I am not happy at all with it. I am unlikely to buy any Radical Firearms product again. Poor quality fit finish overall and it is very picky about the charging handle and bolt carrier used. The interior of the upper and chamber extension were overly tight to the point of being a little out of spec. Fortunately I have a lot of quality spare parts on hand and had to go through most of my spare bolt carrier groups to find one that fit properly and operated smoothly. Same for charging handle. I can't recommend this product and it is the first "lemon" I have received from Primary Arms.