A shotgun, also called a "scattergun," is a firearm designed to shoot a multitude of lead or steel balls of varying sizes, greatly increasing the weapon's hit potential. This makes it very effective at hunting game. However, the accuracy and power found at close range starts to diminish as the target gets farther away. Shotguns designed for the military's use are often called "combat shotguns."
The sawed-off shotgun is a break action, 12 gauge shotgun that fires both shells with a single pull of the trigger. Each shot delivers 14 pellets (instead of the typical 7), and while its damage-per-second is low, it inflicts incredible burst damage at close range. The shotgun's base damage in Fallout: New Vegas is double that of its counterpart in Fallout 3 - in fact, it inflicts more damage per shot than any other non-unique shotgun (Big Boomer inflicts an extra 20 points), and is second only to the anti-materiel rifle as the most powerful non-unique conventional firearm in the game.
However, its incredible damage is offset by the fact that it has an extremely wide spread, wider than any other weapon in the game, causing little to no damage beyond normal melee range. In addition, because it fires both barrels at once it wears out fast, eats up more ammo than other shotguns, and must be reloaded after each shot, leaving the player vulnerable between shootings (even with its fast reload speed). Thus, the shotgun is best utilized as an unconventional melee weapon rather than a gun: used either in cramped quarters such as tunnels and caves, or taken out to finish off a charging enemy before they get too close.
Furthermore, it is also considered an improved holdout weapon, and can be concealed and carried into weapon-free locations, so long as your Sneak skill is 50 or greater.
The sawed-off shotgun can fire a total of about 395 times, or 790 standard rounds, the equivalent of 395 reloads, from full condition before breaking. This amount is exactly the same as its unique variant.