This is a complete Semi-Automatic Shotgun Concept. The dual tube magazines each hold a different type of ammo (ammunition). Typically,
one mag-tube would hold the primary ammo type, such as a "fletchette" or "buckshot" load. The other mag-tube would hold the secondary ammo type, a "slug" or
"explosive" projectile. The weapon fires in "self-load" gas operated operation, while the pump action forearm selects the magazine, thus the ammo, to be fired.
The forearm in the forward position would select the primary ammo type, and in the aft position would select the secondary ammo.