FMK Firearms AR-1 eXtreme 5.56mm NATO Semi-Auto Rifle | Lightweight Polymer Lower, 16" Threaded Barrel
The FMK AR-1 eXtreme pairs a weight-saving polymer lower with a Mil-Spec upper to deliver a lighter, highly compatible AR-15 pattern rifle. Built entirely in the USA, this 5.56mm NATO carbine offers a 16-inch threaded barrel, a carbine-length quad-rail for accessories, and a six-position collapsible stock that adapts to different shooters or gear setups.
Condition
Overall Condition: Good – Shows some signs of prior use and handling.
Bore Condition: Excellent – Clean, mirror finish, no signs of wear.
Rifling Condition: Excellent – Sharp lands and grooves.
Specific Condition Notes: Only minimal handling marks are present on the receiver and handguard; finish remains uniform with no structural damage observed.
What’s Included
- FMK AR-1 eXtreme 5.56mm NATO rifle
- One 30-round polymer AR-15 magazine with hex-scale textured panels
The AR-1 eXtreme lower receiver is molded from impact-resistant polymer that weighs roughly 60% less than a forged aluminum lower. Designed to flex rather than crack, it keeps overall weight down while retaining full compatibility with standard Mil-Spec parts.
A 16-inch barrel with a 1:8 twist handles the full range of 5.56 NATO and .223 Remington bullet weights. The muzzle is threaded 1/2x28, ready for standard flash hiders or other muzzle devices.
The upper receiver is forged from 7075-T6 aluminum and finished with durable black anodizing. A fixed A2 front sight provides a proven reference point; the flat-top rail behind it is ready for the buyer’s choice of rear sight or optic.
The carbine-length quad-rail aluminum handguard offers four full-length Picatinny rails for lights, grips, or other accessories. Coupled with the six-position collapsible stock and A2-pattern pistol grip, the rifle can be adjusted quickly for different body types or mission requirements.
FMK manufactures the AR-1 eXtreme entirely in California, ensuring U.S. sourcing and quality control from raw material to finished rifle.