CQBR
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The Close Quarters Battle Receiver (CQBR) is a replacement upper receiver for the M4A1 Carbine. Its preliminary NATO 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 (666 mm). The CQBR entered service in 2000.
Background
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 of the CQBR remains to provide operators with a weapon of submachine gun size, but firing a rifle cartridge, for scenarios such as VIP protection, urban warfare, and other close quarters battle (CQB) situations. The CQBR is designed to provide improvement over previous AR-15/M16-type weapons in this category. The CQBR is usually issued as a complete weapon system, and not just an upper receiver. The CQBR was once only available to Naval Special Warfare units, but the Mk 18 Mod 0 has become general issue for Visit, Board, Search, and Seizure (VBSS) missions.
The short 10.3 in (262 mm) barrel length requires special modifications to reliably function. The gas port is opened from 0.062 to 0.070 in (0.16 to 0.18 mm). A one-piece McFarland gas ring replaces the three-piece gas ring set. The standard 4-coil extractor spring is replaced with a commercial off-the-shelf (COTS) 5-coil spring. An O-ring surrounds the extractor spring.
Specifications
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- Upper and Lower Receiver: The lower receiver is a standard M4A1 lower receiver with no modifications. Internally, the CQBR also takes advantage of a larger gas port and modified bolt carrier and buffer assembly. The gas port has been opened to 0.070 in (0.18 mm). The charging handle is a PRI M84 Gas Buster charing with a Big Latch.
- Sights: Initially, detachable carrying handles cut down so that only the rear sight assembly, were used. However, most of these have been replaced with the similar commercially-made Lewis Machine & Tools rear sight.
- Stock: A variety of M4 retractable buttstocks are used on a standard 4-position receiver extension. Most often seen is the SOPMOD stock, often referred to as the 'Crane stock', created by Dave Armstrong of NSWC-Crane. The angled stock offers better cheekweld as well as providing two storage compartments for spare batteries. The stock must be removed off the weapon to access the storage compartments. The initial run of stocks was made by NSWC-Crane from glass fiber polymer. Because of this, they were somewhat fragile and did not always properly lock into the receiver extension. A rubber band was used to secure the latch, so it would not slide out of the desired position. The current SOPMOD stocks are made by Lewis Machine & Tools and have none of the problems.
- Barrel: The CQBR uses a standard 1:7 in (178 mm) twist M4 barrel that has been reduced in length to 10.3 in (262 mm). The diameter of the barrel under the handguards is 0.625 in (16 mm). The KAC QD flash suppressor is fitted, allowing use of the KAC QD Suppressor (National Stock Number 1005-01-437-0324). Although it has a bayonet lug, the CQBR is not meant to be fitted with one.
- Handguards: The standard handguard for the CQBR is the Knight's Armament Company Rail Interface System (RIS; National Stock Number 1005-01-416-1089), which allows for the usage of any accessories that are compatible with MIL-STD-1913 Picatinny rails.
- Ammunition: The CQBR is designed to use standard 5.56 x 45 mm NATO 62-grain M855 FMJ and M856 Tracer ammunition. However, due to the short barrel, the heavier 77-grain Mk 262 cartridge is preferred. There are no plans to rechamber the weapon in any additional calibers.
Photos
See also
- AR15 and M16 rifles and M4A1 carbine
- United States Navy Mark 12 Mod 0 Special Purpose Rifle
- List of individual weapons of the U.S. Armed Forces
- Knight's Armament Company
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