The M26 MASS (Modular Accessory Shotgun System) is an under-barrel shotgun available to the Assault class at 18,000 points. The M26 MASS is initially loaded with standard 12-gauge buckshot ammo. Additional ammo types are unlocked as one progresses through the Assault class unlocks. Like with the M320, only one type of ammunition can be equipped in a loadout at any time. Similarly, a player can only equip either the M26 MASS or the M320, but not both. The M26 MASS uses a straight-pull bolt action and is somewhat slower firing than other shotguns.
The M26 MASS can be equipped as an under-barrel attachment, or as a standalone gadget. Equipping the MASS with the underslung rail will make switching between the primary weapon and the MASS a faster process. When equipped under-barrel, the MASS uses the primary weapon’s site attachment and can benefit from equipped laser sights. When equipped standalone, the MASS is outfitted with a red dot sight. It should be noted that using the M26 MASS contributes to a player’s shotgun score, and can help in unlocking additional shotguns while still having access to an assault rifle while on the battlefield.
The M26 MASS can be equipped with dart ammo at 51,000 Assault class points. The M26 DART uses flechette ammunition, which has a slightly reduced close-range damage compared to the standard buckshot ammunition, but has a lower damage dropoff, making it slightly more effective at range. In Battlefield 3, flechette ammo had a greater penetrating power than buckshot, but it is not clear if that is consistent with BF4. Flechette ammo also has a greater suppressive effect at close range than buckshot.
At 88,000 Assault class points, the player unlocks the M26 SLUG. Loaded with 12 gauge SABOT slug ammunition, the M26 SLUG has an increased range over the first two unlocked ammunition types. Slug ammunition makes the M26 MASS viable in medium range engagements. However, it is not a one hit kill at close ranges, making buckshot and dart ammo preferable for close-quarters combat. At long range, the slug rounds require significant adjustment for the extreme bullet drop.
The last M26 unlock is frag rounds at 114,000 Assault class points. The M26 FRAG is loaded with explosive ammunition for increased suppression, as well as the ability to inflict splash damage to enemies near the impact point. The frag rounds explode on impact. Because of the splash damage inflicted, this ammo is very effective when used on clustered groups of enemies.