"Most encounters with the gringo Paternians are meeting engagements. In the jungle, they are often at ranges between 50 and 100 meters. In such a scenario, we fear their shotgun the most. They load their slugs with buckshot. This means that cover that would stop even a rifle bullet would be punctured completely with it. Because of the buckshot, there is little sense to move from cover, for you are most likely going to be hit by buckshot."
-Sgt. M. Alvarez, Gran Hispanic Army, 881st Parachute Regiment.

The Rocker Arsenal M100A1 is an upgrade to the M100 pump-action shotgun already in service. It can fire a variety of 12-gauge ammunition and can accomodate shells up to 3.5" in length, although standard-issue shells are 3" shells. This example has a modified magazine tube cover that allows a Paternian M16 bayonet to be fitted, and has a 6+1 capacity. From left-right in the third image is the following shells in service: birdshot, buckshot, slug, buck and slug (featuring a 1oz slug and six 00 buckshot pellets), rubber buckshot, and explosive ammunition.

Birdshot and rubber buckshot are used for riot control and are employed by firing into the road surface so that they bounce up, scattering the shot and reducing the energies to less-lethal levels. Buckshot, slug, buck and slug, and explosive ammunition are combat loads. The shotgun provides the soldier with a weapon capable of easily breaching doors and clearing out rooms with a combat hit probability only exceeded by designated marksman or sniper rifles.