page_title: Close Quarters Battle Receiver
section_title: Specifications
hierarchical_section_title: Close Quarters Battle Receiver / Specifications
caption_attribution_description: English: VIRGINIA BEACH, Va. (June 5, 2007) - U.S. Navy SEALs (Sea, Air, Land) perform a live fire exercise for the Secretary of the Navy (SECNAV) The Honorable Dr. Donald C. Winter at the Naval Amphibious Base Little Creek's shooting facility. U.S. Navy photo by Chief Mass Communication Specialist Shawn P. Eklund (RELEASED)
context_page_description: The Close Quarter Battle Receiver is a replacement upper receiver for the M4A1 Carbine, developed by the US Navy. The CQBR features a barrel 10.3 in in length, similar to the Colt Commando short-barreled M16 variants of the past. This shorter barrel makes the weapon significantly more compact, which makes it easier to use in and around vehicles and in tight confined spaces. Special units such as commandos boarding ships and bodyguards for senior officers have found such shortened weapons very useful and use the CQBR.
  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. With the stock retracted, the overall length of the weapon is 26.75 inches.
context_section_description: Upper and lower receivers: The lower receiver is a standard M4A1 lower receiver sometimes modified with the addition of a CQD RSM sling adapter plate. However, many CQBR rifles also use surplus M16A1 lower receivers. 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 (1.8 mm). A number of Lewis Machine & Tool 10.5" (266.7 mm) upper receivers have also been reported to have been purchased for the CQBR program. These upper receivers feature a gas system optimized for short barrel use. The Mod 1 makes use of a forward sight delete and full-length handguard to provide more rail space for the user.
  Sights: Initially, detachable carrying handles cut down so that only the rear sight assembly was used. However, most of these have been replaced with the similar, commercially-made Lewis Machine & Tool adjustable rear sight. Also used are several types of reflex and magnified optics, most commonly seen is the Aimpoint CompM2 in a Wilcox Industries Corp. Picatinny (MIL-STD-1913) mount. On the Mod 1, the front sight is deleted and a full-length accessory rail is used; flip up iron sights may be mounted per user preferences
  Stock: A variety of M4 retractable buttstocks are used on a standard 4-position receiver extension, including the standard "CAR" stock. 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 from 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 L7LA2B SOPMOD stocks are made by Lewis Machine & Tools and have none of these problems.
  Barrel: The CQBR uses a 1:7 in (178 mm) twist M4 barrel that has been modified in length to 10.3 in (262 mm). The diameter of the barrel under the handguards is 1.17 in (29.7 mm). The KAC M4-QD flash suppressor is fitted, allowing use of the KAC QDSS-NT4 suppressor (National Stock Number 1005-01-437-0324). Although it has a bayonet lug, the CQBR is not meant to be fitted with a bayonet.
  Handguards: The standard handguard for the CQBR is the Knight's Armament Company Rail Interface System (M4 Carbine RIS; National Stock Number 1005-01-416-1089), which is designed for a variety of barrel profiles and allows for the use of any MIL-STD-1913 tactical accessories such as the AN/PEQ-2 infrared pointer, SureFire flashlights, or a vertical forward grip.
  The handguard manufacturer has since changed from KAC to Daniel Defense as the primary contractor for the MK18 RIS, NSN # 1005-01-548-1385.
  Ammunition: The CQBR is designed to use standard 5.56×45mm NATO 62-grain SS109/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.
caption: Navy SEALs conduct Shoot House Training at Little Creek, Virginia in mid 2007. Each Mk18 Mod 0 CQBR carbines has the M68 Aimpoint optic, Knight's Armament QD suppressor and AN/PEQ-2.
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