The FMK Firearms AR-1 (brand part no. FMKGAR1E) is a stripped AR-15 lower receiver chambered in .223 Remington/5.56 NATO and manufactured in the USA from a high-impact proprietary composite polymer rather than aluminum. FMK markets the AR-1 as the strongest composite polymer lower on the market, weighing in at just 4.3 ounces while still delivering the durability builders expect from an AR-15 receiver. The black finish keeps it versatile across most build styles. It’s a lightweight alternative for builders who want to shed weight without moving to a billet aluminum receiver.

Key Specifications

• Molded from a high-impact composite polymer rather than aluminum.
• Chambered in .223 Remington/5.56 NATO, the standard AR-15 chambering pair.
• Runs a semi-automatic action, standard for AR-15-pattern builds.
• Weighs approximately 4.3 ounces, notably lighter than an aluminum receiver.
• Finished in black for a versatile appearance.
• Sold as a stripped receiver, giving full control over trigger and safety selection.
• Manufactured in the USA.
• Compatible with mil-spec uppers spanning calibers from .22 LR up to .50 Beowulf.

Frequently Asked Questions

Is this receiver made from aluminum? No, it’s molded from a high-impact composite polymer rather than aluminum.

How much does it weigh? Approximately 4.3 ounces, notably lighter than a standard aluminum lower.

Buy the FMK AR-1 Polymer AR-15 Lower Receiver

Shed weight without sacrificing durability, part of our AR15 lowers selection. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.