A shotgun, also called a "scattergun", is a firearm designed to shoot a multitude of projectiles with a single pull of the trigger. This makes it very effective at hunting game, greatly increasing the weapon's hit potential. However, the accuracy and power found at close range diminish rapidly as you get farther away from the target. Shotguns designed for military use are often called "combat shotguns".
Unlike the sawed-off shotgun, which has existed in the game since release, the double-barrel has both its barrel and stock intact. Even badly damaged it does more damage than a combat shotgun, but it also fires both barrels at once, which forces you to reload immediately after each shot, however, it has a short reload time of 0.8 seconds. The drawback to this is ammunition consumption, as again, each shot expends two shells.
Because the weapon discharges two shells per shot the weapon deteriorates twice as fast. Starting from a fully repaired gun, it will:
Begin to jam after 50 shots, almost halfway through the guns health, whereas The Terrible Shotgun doesn't do this until 120 shots.
Break after 118 shots, whereas The Terrible Shotgun breaks after 146 shots.
This means that while The Terrible Shotgun has only two chances to jam after a full spent magazine, the double-barrel shotgun has 57.
Similar to the tri-beam laser rifle in Broken Steel, the double-barrel shotgun has an object effect which inflicts an extra 35 damage per hit when used by non-player characters against the player. However, unlike other Point Lookout weapons affected by this additional damage, the double-barrel shotgun applies this damage per pellet, making it possible for the weapon to apply an extra 315 damage if all 9 pellets strike the player. Additionally, this damage ignores Damage Resistance and is independent of the condition of the weapon, making it especially deadly in the hands of swampfolk and other non-player characters.
One may be found relatively early in the add-on inside the Naval Recruitment Center. You can also find one in the Wrecked Sea Tub in a surfaced wooden boat containing a skeleton, shotgun shells, and pre-War money.
It is also obtainable at the Homestead Motel, in the main lobby behind the counter and in Room 1G.
The double-barrel shotgun was slated for inclusion in Fallout: New Vegas at some point during development. While it was either removed prior to the release of the game or never implemented to begin with, a number of resources remain in the game's files for the weapon, including the weapon model and firing sounds, as well as an unused Form List, RepairNVDoubleBarrelShotgun. The weapon model and associated animations are identical to those found in Point Lookout, meaning the weapon lacks iron sights and the multi-step reload sound effect used for compatibility with the Rapid Reload perk. Despite this, sufficient resources exist for the weapon to be fully implemented within the game, leaving the ultimate reason for its exclusion unclear.