FN 15 Military Collector M4 Stripped Lower Receiver

The FN 15 Military Collector M4 Stripped Lower Receiver is the closest civilian receiver to a service M4 carbine, because FN builds the actual M4s and M16s the U.S. military issues. The Military Collector series, released in November 2023, takes the same forged 7075-T6 receiver FN runs on its government contracts, machines and broaches it to mil-spec, and applies the roll markings of FN's U.S. Military M4 production receivers. The only functional change is a fire control housing modified to block select-fire, so the receiver is semi-auto only.

For a clone build, the roll mark is the entire point. The Aero Precision M4E1 is the popular upgrade lower, but its integrated trigger guard, flared magwell, and billet-style flat sides read as a modern enhanced receiver, not a service M4A1. The FN 15 keeps the standard mil-spec M4/M16 contour with the separate trigger guard and unflared magwell of a contract carbine, so a finished clone looks correct from the magwell back.

This entry is the M4-marked variant (SKU 20-100821), the right choice for an M4 or M4A1 carbine clone. FN also sells the same receiver with M16 markings (SKU 20-100822) for fixed-stock rifle clones. Both accept any mil-spec lower parts kit, buffer assembly, and stock interface, so the rest of a SOPMOD or retro parts list bolts up directly.