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M26 Modular Accessory Shotgun System
PEO M26 MASS on M4 Carbine.jpg
The M26 MASS mounted on the M4 carbine.
Type Shotgun
Place of origin United States
Service history
In service 2003–present
Used by United States
Wars Iraq War
Production history
Designer Ira Kay
Designed 2000s
Manufacturer C-More Competition
Produced 2011
Variants XM26
Weight 3.31 lb (1.5 kg)
Length 19.7 in (500 mm) stock extended/13.8 in (350 mm) stock folded
Barrel length 7.75 in (180 mm)

Caliber 12 gauge
Action Manually operated straight-pull bolt action
Feed system 3 or 5 round detachable box magazine
Sights None; MIL-STD-1913 rail provided for optics

The M26 Modular Accessory Shotgun System (MASS) is a developmental under-barrel shotgun attachment for the M16/M4 family of United States military firearms. It can also be fitted with a pistol grip and collapsible buttstock to act as a stand-alone weapon. It is replacing the current M500 shotguns in service.[1]


Soldier with M26 MASS.

Left side of M26 showing bolt handle.

The M26 MASS is a militarized version of the Lightweight Shotgun System, developed by C-More Systems and manufactured by Vertu Corporation[2] and originally marketed toward special operations forces. It attracted the interest of soldiers being deployed to Afghanistan who wanted to reduce the number of individual weapons they had to carry by using a shotgun as a rifle attachment instead of a discrete weapon.

The M26 has 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 under 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 Masterkey (KAC Masterkey) system, which dates back to the 1980s and originally comprised a shortened Remington 870 shotgun mounted under an M16 rifle or M4 carbine. The M26 improved upon the original Masterkey concept with a detachable magazine option and more comfortable handling, thanks to a bolt-operated system. The detachable magazine offers quicker reloading and a quicker change of ammunition types. 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 bolt handle can be mounted on either side of the weapon. The M26 was chosen by the U.S. Military over the Masterkey as a breaching tool.[3] At the present time, small numbers of M26 MASS shotguns have been issued to U.S. troops in Afghanistan. The current contract calls for the delivery of 9,000 shotguns.[1] In February 2012, the first unit was fully equipped with M26s.[4]

War in Afghanistan

The shotgun is currently in low rate initial production.[5] In May 2008, the Army announced it would procure 35,000 units.[6] The first M26 shotguns were procured and fielded to military police and engineer units in 2010. However, some units in both Iraq and Afghanistan were issued the M26 in small quantities as early as 2003.[7] Full initial fielding began in 2011.[8]


Stand-alone M26 MASS

  • Caliber: 12 gauge
  • Operation: Straight pull bolt-action.
  • Capacity: 3 or 5 round detachable magazine.
  • Ammunition: 2.75 and 3 in lethal, non-lethal and breaching rounds.
  • Barrel length: 7.75 in (197 mm) with integral breaching stand-off adapter.
  • Under-barrel version:
    • Overall length: 16.5 in (419 mm)
    • Weight: 2 lb 11 oz (1.22 kg)
  • Stand-alone version:
    • Overall length: 24 in (610 mm) (stock collapsed)
    • Weight: 4 lb 3 oz (1.90 kg)

See also


  1. 1.0 1.1 Dan Parsons (January 2013) Army, Marine Corps Succeed in Rapidly Fielding Specialized Individual Weapons (UPDATED). National Defense Magazine
  2. US Army’s M26 Mass 12 Gauge. Retrieved on 2013-01-22.
  3. The C-MORE M26 may be available to civilians. The Firearm Blog (2010-02-16). Retrieved on 2013-01-22.
  4. 101st Airborne's 'Strike' brigade first Army unit issued M26 shotgun | Article | The United States Army. (2012-02-17). Retrieved on 2013-01-22.
  5. Tim Chyma (2007-05-07) PM Individual Weapons Overview for the Small Arms Symposium & Exhibition. National Defense Industrial Association
  6. U.S. Army set to buy 35,000 M-26 Rifle/Shotguns. Retrieved on 2013-01-22.
  7. Lance M. Bacon (30). "Improved carbines headed your way". Gannett Government Media Corporation. Retrieved 30 April 2011. 
  8. Fuller, BG Peter N.; COL Douglas A. Tamilio (18 MAY 2010). "Project Manager Soldier Weapons Briefing for NDIA". PEO Soldier. United States Army. Retrieved 28 October 2010. 

External links

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