Colt 9mm SMG

The Colt 9mm SMG is a closed bolt, blowback operated SMG, rather than the conventional direct impingement gas operation of the standard 5.56×45mm M16 type rifle.^[6] As a closed bolt weapon, the Colt SMG is inherently more accurate than open bolt weapons such as the Israeli UZI.^[7]

The overall aesthetics are identical to most M16 type rifles. Changes include a large plastic brass deflector protruding from the rear quarter of the ejection port, and a correspondingly shorter dust cover. Factory Colt 9mm SMGs are equipped with a 10.5 inch length barrel and have an M16 style upper receiver, which means they feature a fixed carry handle, no forward assist and A1 sights (with 50 and 100 meter settings). The magazine well of the receiver is modified with pinned-in blocks to allow the use of smaller 9 mm magazines. The magazines themselves are a copy of the UZI magazine, modified to fit the Colt and lock the bolt back after the last shot.^[8]

Current Colt production models are the R0635 (RO635) which features a Safe/Semi/Full Auto selective fire trigger group and the R0639 (RO639) which features a Safe/Semi/3-round Burst selective fire trigger group. Both are equipped with a 10.5 inch length barrel. The 633 was a modified compact version with a 7 inches (180 mm) barrel, hydraulic buffer and simplified front sight post used by the DEA and the Department of Energy.^[9][10]

The most common model is the 635, the latest version of which are simply marked SMG 9mm NATO.^[11] Until early 2010s, there are newer variants, R0991(RO991), R0992(RO992) and R6951 are introduced. The R0991 features Safe/Semi/Full Auto selective fire is constructed with Rail Integration System (RIS) picatinny rails on the flat-top receiver as well as around the barrel which allows the easy mounting of ancillary devices, has 10.5" barrel and equipped with a third generation composite buttstock; The R0992 has almost all the same features to the R0991, except the selective fire mode is Safe/Semi/3-round Burst only; The R6951 has almost all the same features of the R0991 and R0992, but doesn't have selective fire and has a 16.1" barrel instead of the 10.5" one.

A suppressed variant known as the "DEA model" exists that uses an integral Knights Armament Company made suppressor covered with an M16A2 handguard.^[12]

In 2025, Harrington & Richardson has released their clone of the Colt 633 SMG.^[13][14]

• Argentina: Used by the Argentine Army.^[15]
• Ecuador^[16]
• India: Used by the Octopus Unit of Andhra Pradesh Police.^[17]
• Israel: Used by IDF special forces.^[18]
• Malaysia: Used by the Pasukan Khas Udara (PASKAU) Counter-Terrorism Forces of the Royal Malaysian Air Force^[19]
• Mexico^[20]
• United States: Used by the United States Marine Corps,^[a][21][22] United States Marshals Service, Los Angeles Police Department Metro Division SWAT, Federal Bureau of Prisons, Drug Enforcement Administration, Diplomatic Security Service, Department of Energy Federal Protective Forces, and a number of other federal agencies.^[23][24]

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  Colt SMG 635 left side
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  Colt SMG 635 right side
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  Colt SMG 635, ML 2 Sight, Colt mount, and a magazine
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  Colt SMG 635, ML 2 Sight, Colt mount

• AUG 9mm – Austrian bullpup assault rifle
• FAMAE SAF – Chilean submachine gun
• Heckler & Koch MP5 – German 9×19mm Parabellum submachine gun
• La France M16K
• PP-19 Bizon – Russian submachine gun
• PP-19-01 Vityaz – Russian submachine gun
• QCW-05
• Sterling SAR-87
• TSB17-9