The M4 carbine is a gas-operated, magazine-fed, 5.56x45mm NATO carbine designed in the United States in the '80s. It is a shortened version of the M16A2 assault rifle. Colt has produced many M4 civilian variations and lines over the years, each of which is distinguished by a four-digit number that comes after a specific prefix (LE, CR, etc.). With the introduction of the Colt LE (Law Enforcement) M4 Carbine semi-auto rifle, the battle-tested M4 platform takes a tactical turn. The Colt LE6920 is a series of 5.56x45mm NATO-chambered semi-automatic AR-15 M4 Carbine versions. It is designed for civilian use, whereas the M4 is a select fire weapon, and the 6920 has a 16-inch barrel to comply with US gun laws, while the M4 has a 14.5-inch barrel. M4 civilian copies often feature 16-inch barrels (or regular 14.5-inch M4 barrels with flash suppressors permanently attached, for a total length of 16 inches) and are semi-automatic, just to fit the legal definition of a rifle under the US Gun Control Act. Therefore, the Colt LE6920 features a little longer barrel and a Magpul MBUS in place of the usual carry handle and sight. The 16-inch M4 barrel features 1:7 rate-of-twist rifling and is chrome lined. Both weapons' components, including the bolt, the bolt carrier group, the trigger, the barrel, and the springs, are strong and long-lasting and meet military standards. While the Colt 6920 series currently comes with a darker black finish, older versions had a slightly lighter black finish. Colt LE M4 Carbine comes with one 30-round magazine, while some other civilian M4 models, like CR, use 10 or 15-round magazines. The Colt OEM Series provides customers and dealers with an unconditional alternative for customizing rifles based on the tried-and-true Colt M4 Platform. In OEM1 and OEM2 versions, handguards, buttstocks, trigger guards, magazines, and rear sights have been completely removed.