A partial-fence M16 lower receiver in 80% form — 7075 aluminum, machined by Potomac Armory to the early-1960s Colt geometry, ready for the end user to finish into a period-correct retro build.
The partial-fence lower is the middle chapter of the early M16 receiver story. The first production Colts — the Model 601 "Slabside" and Model 602 — ran a completely smooth magazine well with non-captive pivot pins. Field reports from Vietnam pushed Colt to add a small raised housing at the front of the magazine well that captured the spring and detent for the front pivot pin. That housing is the "partial fence," and it shows up on early Vietnam-era Colts beginning in late 1963 — the Model 603 (XM16E1/M16A1 early pattern), 604, 605, and 609 variants — through approximately 1967, when the full-length magazine fence of the mature M16A1 replaced it.
A builder chasing a 1964–1967 retro M16A1 clone, a Model 603 XM16E1 replica, or any Vietnam-period Colt needs this receiver profile — a later full-fence lower is historically wrong for the era and reads wrong to anyone who studies the platform. This lower fills that gap at the 80% stage so the builder can finish the receiver themselves as a personally-made firearm, with the legal and retro-authenticity advantages that come with that path.
An 80% lower is a piece of 7075 aluminum that has been roughly machined but does not yet meet the federal definition of a firearm. The fire-control pocket, trigger-pin holes, and selector-hole bore are the finishing steps the end user completes. Under current ATF guidance, a personally-made firearm must be finished by the individual who will own it — third-party machining services are not permitted on an 80% receiver intended to become a firearm. Charlie's does not sell finishing jigs, CNC tooling, or Ghost Gunner machines, and Charlie's does not perform the fire-control machining. We provide the raw component and optional pre-finishing services (engraving, anodizing) on the unfinished aluminum only.
Charlie's runs fiber lasers in-house and can deep-engrave, light-engrave, or surface-etch period-correct markings on the unfinished aluminum. Colt-style rollmarks, decorative motifs, or customer-supplied artwork are all options. We only engrave on 80% receivers — never on completed firearms — because markings on a finished receiver can mislead a future buyer about the true manufacturer. For anodizing, we can run the lower in black or Colt-gray (the more expensive Vietnam-era finish) as part of our batch schedule every one to two months, or as a one-off for a higher service fee. Reach out for a quote before you add to cart.
We carry this lower because Vietnam-era clones are part of what Charlie's does, and sourcing a correct partial-fence receiver is the single hardest step in most 603 or early A1 projects. Add the engraving or anodizing service in the same order and we'll run them together — contact us first for the quote and lead time.
Tactical Machining
