The M26-MASS (Modular Accessory Shotgun System) is a shotgun configured as an underbarrel ancillary weapon attachment mounted onto the handguard of a service rifle, usually the M16/M4 family of United States military, essentially making the host weapon a combination gun. It can also be operated as a stand-alone shotgun by attachment to a pistol grip/collapsible buttstock module. Rollout commenced in 2013, replacing the M500 shotguns in service. Development The M26-MASS is a lightweight underbarrel shotgun configured to be secured to a main rifle, developed by C-More Systems and manufactured by Vertu Corporation and originally marketed toward special operations forces. It attracted the interest of soldiers being deployed to Afghanistan who wanted a lightweight system that could eliminate the need to carry additional weapons. The M26-MASS had been in development at the U.S. Army's Soldier Battle Lab since the late 1990s. The idea was to provide soldiers with lightweight accessory weapons which could be mounted underbarrel of the standard issue M16 rifle or M4 carbine. These would provide soldiers with additional capabilities, such as: door breaching using special slugs, very short-range increased lethality using 00 buckshot, and less-lethal capabilities using teargas shells, rubber slugs, rubber pellets, or other non-lethal rounds. The original idea was based on the Knight's Armament Company Masterkey system, which dates back to the 1980s and originally comprised a shortened, tube-fed Remington 870 shotgun mounted under an M16 rifle or M4 carbine. The M26-MASS improved upon the original Masterkey concept with a detachable magazine option and more comfortable handling, thanks to a bolt-operated system which is manually cycled for reloading and is characterized by a bolt which must be moved backward to remove a spent case and forward to chamber a new cartridge. The relatively large bolt handle is located closer to the rear rather than the slide on the Masterkey pump shotgun, and thus is easier to cycle in combat. The handle can be easily attached on either side of the bolt. The detachable magazine offers quicker reloading and change of ammunition types. The M26-MASS was chosen by the U.S. Military over the Masterkey as a breaching tool. Small numbers of M26-MASS shotguns were issued to U.S. troops in Afghanistan. The current contract calls for the delivery of 9,000 shotguns. In February 2012, the first unit was fully equipped with M26-MASS. At the same time the U.S. Army is in the process of replacing the M500s with