versions were available. The current models are the Model 991, which fires in semiauto or full auto, and the Model 992, which fires in semiauto or a three-round burst. These newer versions feature a flat top upper and quad rail for easy mounting of optics and other accessories. The 10.5-inch barrel has a 1-in-10-inch twist. The rate of fire is listed as between 700 to 950 rounds per minute. These models weigh 6.7 pounds and are 26 inches long with the stock retracted, and 29.25 inches with the stock extended. THE COLT M231 FIRING PORT WEAPON Although the Colt M231 was one of
the most produced, it was the least successful of all M16 variants. The M231 was designed to allow soldiers in the Bradley Fighting Vehicle to fire at the enemy through gun ports without leaving the protection of the vehicle. A standard M16A1 could not be used because the Bradley’s six firing ports featured a screw-type mounting designed to maintain a seal against a chemical weapon attack. The 231 was literally screwed into the fittings from inside the vehicle. The M231 shares about two-thirds of its parts with the parent M16A1 design. As with the 9mm machine gun, the most significant change was the elimination of the M16’s gas
impingement system in favor of a direct-blowback, striker-fired design. This simpler mechanism is typically associated with smaller caliber submachine guns. Instead the M231 is chambered for the 55-grain version of the standard 5.56mm NATO cartridge. The weapon weighs about 7.33 pounds, and has an overall length of 28¼ inches. The barrel is 15.6 inches long with the same 1-in-12inch rifling twist as the M16A1. In addition to being shorter than a M16A1 barrel, the M231 barrel also has a significantly thicker profile. The shortened hand guards end at the distinctive metal locking collar.
The Colt 9mm Submachine Gun was designed to directly compete with the HK MP5 series of SMGs in the law enforcement market. (COLT DEFENSE)
The gun was popular with police agencies for its accuracy and similarity with the M16. (COLT DEFENSE)
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American Shooting Journal // January 2018