Close Quarters Battle Receiver

The Close Quarter Battle Receiver (CQBR) is a replacement upper receiver for the M4A1 carbine developed by the US Navy. The CQBR features a 10.3 in (262 mm) length barrel (similar to the Colt Commando short-barreled M16 variants of the past) which makes the weapon significantly more compact, thus making it easier to use in, and around, vehicles and in tight, confined spaces.