Let's be real: Are you really going to keep those factory handguards on your new Colt M4 Upper Receiver? If not, then why are you paying for them? Get this Colt M4 Upper Receiver Group that ships without handguards, providing you with a blank canvas that accepts the handguards of your choice. Each Colt M4 Upper Receiver Assembly is chambered in 5.56 NATO and is available in 14.5- and 16-inch barrel lengths. The muzzles are all threaded 1/2""-28 TPI, and the barrels feature a standard twist rate of 1:7 inches. The button-rifled barrel is paired with a low-profile gas block that will clear most free-float handguards on the market. A bolt-carrier group and charging handle are included in this upper receiver group.