Colt M4 Upper Receiver, Raised C, Cerro Keyhole — NOS BLEM Grade C

These are New Old Stock 2017 Colt M4 upper receiver assemblies from the final period of the traditional raised-C receiver, using Cerro keyhole forgings. This particular offering is our Grade C, meaning the raised Colt C is present but very faded and lightly formed. The grading concerns the appearance of the C—not the function, machining, or authenticity of the receiver.

For the clone builder, this is an unusual opportunity. These are genuine late-production raised-C Colt uppers from just before Colt's broad transition to CAGE-code markings, but priced according to the cosmetic quality of a marking that collectors normally pay a premium to obtain.

Highlights

• 2017 New Old Stock Colt — From the closing period of Colt's traditional raised-C upper receiver production.
• Grade C Raised C — Genuine Colt C remains present, but is very faded and considerably less distinct.
• Cerro Keyhole Forging — Correct raised keyhole forge identifier from Cerro's Virginia forging operation.
• Cosmetic BLEM Only — Grade reflects the quality of the raised C, not receiver function or machining.
• M4 Configuration — M4 feed ramps and front M4 marking.
• Gray Dry-Film Interior — Military-pattern dry-film lubricant inside the receiver.
• Complete Receiver Assembly — Forward assist and ejection-port cover are installed.
• Clone-Collector Component — Particularly useful for Colt M4, M4A1 and GWOT-period builds where receiver markings matter.

[IMAGE: Close-up of actual Grade C receiver showing the faded raised C and Cerro keyhole]

The End of the Raised-C Era

For years, one of the easiest visual clues on a Colt flat-top upper was the raised C beside the forge identifier. The adjacent keyhole identifies the forging source as Cerro; the C is the Colt marking collectors look for.

This group dates to 2017, very late in the traditional C-marked period. Around 2018, Colt's 13629 CAGE-code markings became increasingly common on upper receivers and other components. As is typical with Colt, there was overlap rather than a single clean production cutoff.

What makes these receivers different is the condition of the forging die.

By this late production run, the portion of the die creating the raised C was no longer producing the tall, crisp mark associated with a fresh die. The receiver itself remained entirely serviceable, but the appearance of the C varied enough that Charlie's separates these receivers into three grades.

Charlie's Raised-C Grading

Grade A — Unblemished

The C is clearly defined and readily visible. We sell these as unblemished receivers. Even on Grade A examples, however, the C is not quite as tall, sharp, or proud as the raised C produced when the forging die was newer. That is characteristic of this late production group rather than a defect in the individual receiver.

Grade B — Blemished

The C remains well defined and easily identifiable, but is noticeably less proud than the C we are accustomed to seeing on earlier Colt forgings. The mark may also display some wear or softness in its edges.

Grade C — Blemished

This listing is for Grade C. The C has become very faded. It remains present, but depending on the individual receiver and lighting, it may require a closer look to see clearly.

That faded C is the reason for the Grade C designation and reduced price.

Nothing about Grade C implies defective M4 feed ramps, improper machining, structural damage, or questionable provenance. These are genuine Colt upper receiver assemblies from the same production group. Charlie's is simply grading the feature that matters most to collectors rather than pretending every example looks the same.

For someone building a Colt clone who values the correct receiver more than a photographically perfect C, the Grade C may actually be the sensible buy. You get the genuine late-production raised-C/keyhole receiver while paying less because the very marking that establishes its period is faint.

Technical Specifications