The Close Quarters Battle Receiver (CQBR)
is a replacement upper receiver for the M4A1 Carbine
. The CQBR replaces the M4 with a barrel 10.3 in (262 mm) length making it the modern equivalent of the Colt Commando
short-barrel M16 variants of the past.
Its preliminary National Stock Number was 1005-LL-L99-5996; however, a complete CQBR-equipped carbine now has the NSN 1005-01-527-2288. The overall length of the upper receiver is 19.25 inches (489 mm). With the stock
retracted, the overall length of the weapon is 26.25 inches (667 mm). The CQBR entered service in 2000.
The M4 and M16 are not ideally suited for all missions, so it was proposed that the modularity of the M16 series would allow a user to replace the upper receiver of an existing weapon with one more suitable to the task. One of two proposed special mission receivers that were planned for inclusion into the SOPMOD
Block II kit, the CQBR has taken off on its own. Like the proposed Special Purpose Receiver, the Close Quarters Battle Receiver has been more or less taken on by the Naval Surface Warfare Center, Crane Division
(often referred to as NSWC-Crane or just "Crane") as its own project following the CQBR's removal from the SOPMOD program. Just as the Special Purpose Receiver morphed into the Special Purpose Rifle, and was type-classified as Mk 12 Mod 0/1
, the complete CQBR-equipped carbine has been type-classified as the Mk 18 Mod 0
The purpose... Read More