M26 Modular Accessory Shotgun System (MASS)
Shotgun Lethality Module (SGLM)
Lightweight Shotgun System (LSS)

The M26 Modular Accessory Shotgun System (MASS) is a lightweight 12-gauge accessory shotgun system. The system provides soldiers with a 12-gauge shotgun accessory attachment with lethal, less-than-lethal and door-breaching capabilities. The M26 MASS can be attached to the M4 carbine and zeroes to the host weapon. It is also designed to operate as a stand-alone system, and comes with a recoil-absorbing, collapsible buttstock. With a Picatinny rail on top, the receiver can be used to mount sighting equipment. The bolt handle is mountable on either side for ambidextrous handling.

The M26 MASS enabled soldiers to transition between lethal and less-than-lethal fires and adds the capability of a separate shotgun without carrying a second weapon. Features include a recoil absorbing buttstock, box magazine, flip-up sights, and an extendable stand-off device for door beaching.

First developed with the M4 carbine specifically in mind, the system was known as the Lightweight Shotgun System. It later became an element of the Objective Infantry Combat Weapon's Increment 1, referred to as the Shotgun Lethality Module (SGLM). The weapon was intended to be able to attach underneath the barrel of the M4 and M16 Modular Weapon Systems (MWS), and the Objective Individual Combat Weapon Increment I, just like the M203 grenade launcher. It would provide the capability to fire lethal, non-lethal and door breaching 12 gauge rounds. It could be zeroed to the sighting system of the host weapon.

The Lightweight Shotgun System was designed to fire 2.75 and 3-inch lethal, non-lethal and door breaching rounds, weighed slightly less than 3 pounds, and had a detachable 5-round magazine. It attached to the M4 carbine as an accessory and included a standoff device for firing door-breaching rounds. It was also able to be used as a stand-alone system. It was light, becoming the lightest weapon available to soldiers in the Army besides a pistol.

The system had a 5-round, box-magazine fed, manually operated shotgun. It used a straight push-pull type bolt action that could be switched for either left or right-handed users. The attachment variation was 16.5 inches in length and used the host weapon's sights. It was capable of firing lethal, non-lethal and breaching rounds. The shotgun stand-alone version was converted from the attachable version. It had a pistol grip and a buttstock. The stand-alone version weighed 4 pounds, 3 ounces and was 24 inches long with its stock collapsed. This version also had a reversible charging handle and was capable of firing lethal, non-lethal and breaching rounds.

Previously, soldiers performing non-lethal and door-breaching missions would have carried 2 separate weapons, an individual combat weapon and a separate shotgun. This lightweight, multi-use shotgun would provide soldiers with the capability to breach doors quickly and efficiently without requiring them to carry an additional weapon. The LSS, fastened beneath the barrel of an M4 carbine, eliminated the need for a second weapon.

Soldiers could use the shotgun as an all-around tool in an urban environment. They could use the non-lethal and breaching capabilities, and the big advantage was that they did not have to sling their primary weapon to do it. You had combatants and noncombatants together in a crowd and the non-lethal capability was a good way to neutralize them, whether or not they were armed. Many units in the field expressed the need for a tool like this and it was expected to get a lot of use. It was more accessible and easier than having to switch weapons.