Colt 9mm SMG
Closed-bolt M16-based 9mm SMG used by U.S. federal agencies.
The Colt 9mm SMG, designated the Model 635 or M635, is a submachine gun chambered in 9×19mm Parabellum and built by Colt around the M16 rifle's design. Unlike the standard M16's direct impingement gas system for 5.56×45mm rounds, this weapon uses a closed bolt and blowback operation. Its closed bolt design gives it better inherent accuracy than open bolt submachine guns like the Israeli UZI.
Visually, it closely resembles most M16-type rifles. Key differences include a large plastic brass deflector at the rear of the ejection port and a shorter dust cover. Factory models come with a 10.5-inch barrel and an M16-style upper receiver featuring a fixed carry handle, no forward assist, and A1 sights calibrated for 50 and 100 meters. The magazine well has pinned-in blocks to accept smaller 9mm magazines, which are modified copies of UZI magazines that also lock the bolt open after the last round.
Current production includes the R0635 (RO635) with Safe/Semi/Full Auto fire modes and the R0639 (RO639) with Safe/Semi/3-round Burst. Both have 10.5-inch barrels. The 633 is a compact variant with a 7-inch barrel, hydraulic buffer, and simplified front sight, used by the DEA and Department of Energy. The most common model is the 635, with later versions simply marked "SMG 9mm NATO." By the early 2010s, newer variants appeared: the R0991 (full auto) and R0992 (3-round burst) both feature a flat-top receiver with RIS Picatinny rails around the barrel and a third-generation composite buttstock; the R6951 lacks selective fire and has a 16.1-inch barrel instead of 10.5 inches. A suppressed "DEA model" uses an integral Knights Armament Company suppressor under an M16A2 handguard. In 2025, Harrington & Richardson released a clone of the Colt 633 SMG.
Users include the Argentine Army, Ecuador, India's Andhra Pradesh Police Octopus Unit, Israeli special forces, Malaysia's PASKAU counter-terrorism unit, Mexico, Pakistan, and various U.S. agencies such as the Marine Corps, Marshals Service, LAPD Metro SWAT, Federal Bureau of Prisons, DEA, Diplomatic Security Service, and Department of Energy Federal Protective Forces.
Quick Facts
- Is Ranged
- yes
- Origin
- United States
- Service
- 1982–present
- Wars
- Invasion of Panama / Miami drug war
- Length
- 730 mm (28.9 in ) (stock extended) / 650 mm (25.6 in) (stock retracted)
- Action
- blowback, closed bolt
- Part Length
- 10.5 in
- Feed
- 20- and 32-round detachable box magazine · 100-round Beta C-Mag
- Cartridge
- 9×19mm Parabellum
- Rate
- 700-1000 round/min
- Weight
- 2.61 kg (5.75 lb) w/o magazine
- Velocity
- 396 m/s (1300) ft/s)
Facts from the source article.
Lore & Background
The Colt 9mm SMG retains the overall aesthetics of most M16 type rifles, with changes including a large plastic brass deflector protruding from the rear quarter of the ejection port and a correspondingly shorter dust cover. Factory models are equipped with a 10.5 inch barrel and have an M16 style upper receiver with a fixed carry handle, no forward assist, and A1 sights with 50 and 100 meter settings. The magazine well is modified with pinned-in blocks to accept smaller 9 mm magazines, which are copies of the UZI magazine modified to fit the Colt and lock the bolt back after the last shot.
Current Colt production models include the R0635 (RO635) with Safe/Semi/Full Auto selective fire and the R0639 (RO639) with Safe/Semi/3-round Burst. The 633 was a modified compact version with a 7 inch barrel, hydraulic buffer, and simplified front sight post used by the DEA and the Department of Energy. Until the early 2010s, newer variants were introduced: the R0991 (full auto with Rail Integration System picatinny rails on a flat-top receiver and around the barrel, 10.5" barrel, third generation composite buttstock); the R0992 (same features but Safe/Semi/3-round Burst); and the R6951 (same features but no selective fire and a 16.1" barrel). A suppressed variant known as the "DEA model" uses an integral Knights Armament Company made suppressor covered with an M16A2 handguard. In 2025, Harrington & Richardson released their clone of the Colt 633 SMG.
Reader's Guide
The Colt 9mm SMG occupies a notable niche as a blowback-operated, closed-bolt submachine gun derived from the M16 rifle platform. Its design allows users familiar with the M16 to transition with minimal training, while the closed bolt operation provides greater accuracy than open bolt designs like the UZI. The weapon saw adoption by a wide range of U.S. federal agencies, including the United States Marine Corps, United States Marshals Service, Los Angeles Police Department Metro Division SWAT, Federal Bureau of Prisons, Drug Enforcement Administration, Diplomatic Security Service, and Department of Energy Federal Protective Forces, as well as military and police units in Argentina, Ecuador, India, Israel, Malaysia, Mexico, and Pakistan. The introduction of flat-top receiver variants with Rail Integration Systems in the early 2010s modernized the platform for accessory mounting, while the compact 633 variant served specialized federal units. The 2025 clone release by Harrington & Richardson indicates continued interest in the design. Its significance lies in bridging the M16 ergonomic family with a 9mm submachine gun role, offering a familiar alternative to dedicated SMGs like the Heckler & Koch MP5.
Did You Know?
- The Colt 9mm SMG is a closed bolt, blowback operated weapon, not gas-operated like the standard M16.
- Its magazines are modified copies of the UZI magazine, adapted to lock the bolt back after the last shot.
- The 633 compact variant had a 7-inch barrel and was used by the DEA and the Department of Energy.
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