The XM26 Lightweight Shotgun System (LSS) is a developmental under-barrel attachment type shotgun for the M16/M4 family of United States service firearms.
The shotgun can also be fitted with a collapsibile buttstock and a pistol grip to act as a stand-alone weapon.
The XM26 LSS was originally designed and developed by C-More Systems to meet the requirements of United States troops in Afghanistan for a lightweight less lethal and door breaching delivery system which would eradicate the need to carry an additional weapon such as a pump-action shotgun.
The XM-26 Lightweight Shotgun System has been in production and development at the United States Army's Soldier Battle Lab since late 1990s. These shotguns are manufactured by the prominent C-More Systems company. The concept was to equip soldiers with lightweight accessory weapon, which could be mounted under the generic issue infantry rifle (M16A2 or M4A1 carbine), and additionally provide soldiers with more capabilities, such as: very short-range increased lethality; door breaching using special slugs; using 00 buckshot; rubber slugs and buckshot, less-lethal capabilities using tear gas shells, and other less-lethal rounds.
The original idea has been based on the standard Masterkey system, dated back to 1980s, which initially included the shortened Remington 870 shotgun mounted under the M16 rifle or carbine. The XM-26 improved upon the original Masterkey concept with the more comfortable handling, a detachable magazine option, thanks to bolt-operated system. Detachable magazine generally offers more rapid ammunition type change and quicker reloading; the relatively large bolt handle is located closer to the rear of the weapon, than the slide on the pump-action shotgun in the Masterkey configuration, and thus is much more comfortable to cycle in combat. The bolt handle could be mounted on either side of the shotgun. At the present time small numbers of XM26 LSS shotguns are issued to United States troops in Afghanistan, and, according to gunslot sources, these weapons are well received by troops who used them.