Colt 9mm SMG in "Model 633" Configuration, Class III/NFA Fully Transferable Machine Gun, with Extra Upper Receiver Assembly

A distinctive Colt Model 633 SMG with strong law-enforcement and federal-agency collector appeal, this carbine stands out for its AR-15-based design, specialized configuration, and association with Department of Energy and Drug Enforcement Agency contracts.

• Developed in 1985, the Colt SMG was created for the American law enforcement market as a domestic alternative to the Israeli Uzi and German MP5
• Built on Colt’s AR-15 rifle platform, making the controls and operation nearly identical to the familiar AR-style system
• Designed as a straight-blowback, pistol-caliber automatic carbine—a simple and proven operating system well suited to compact shoulder-fired firearms
• Model 633 configuration:
  • Uses a slightly shorter barrel than the standard Colt SMG
  • Features a different front sight and handguard arrangement
  • Chiefly associated with Department of Energy and Drug Enforcement Agency contracts, adding meaningful federal-service provenance and collector interest
• Sight system:
  • Folding post front sight
  • Two-leaf rear sight
• Forearm and front-end features:
  • Truncated round forearm
  • Steel plate hand stop installed at the end of the forearm
• Magazine well:
  • Pinned-in two-piece adapter block installed in the magazine well
• Controls and receiver features:
  • Right-handed “SAFE/SEMI/AUTO” selector switch
  • A1-pattern upper receiver
  • No forward assist
  • Extended plastic case deflector
• Furniture:
  • Checkered pistol grip
  • Two-position telescoping buttstock
• Included extra upper receiver:
  • 10-inch barrel
  • A1-pattern flash hider
  • Bayonet lug
  • Ribbed round handguard

With its specialized Model 633 features, AR-family handling, federal-agency associations, and included extra upper receiver, this Colt SMG offers notable desirability for collectors focused on modern U.S. law enforcement and government-contract firearms.