The Colt 9mm SMG is a closed bolt, blowback operated SMG, rather than the conventional direct impingementgas 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]
Variants
Further information on Colt 9mm SMG variants: AR-15 variants
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]
^"Colt Weapon Systems". 2003-05-18. Archived from the original on 2003-05-18. Retrieved 2016-11-07.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
^Technical Memorandum 2-79. AIMING POINT DISPLACEMENT FROM FIRING A RIFLE FROM THE OPEN-BOLT POSITION.
by Dominick J. Giordano I. February 1979. U.S. Army Human Engineering Laboratory 1, U. S. ARMY HUMAN ENGINEERING LABORATORY, Aberdeen Proving Ground, Maryland 21005