The Double-barreled Shotgun has the lowest magazine capacity in the shotgun family, but each round fired is just as powerful as the M1014 or Remington 870 (Flashlight). It uses the same type of round as the other shotguns, but it only holds two shells instead of eight. Because of this limitation, its generally considered one of the worst gun in DayZ. It is not entirely worthless, however; the two shells it holds may be fired almost simultaneously, which can instantly kill or seriously injure a player within 40m if pellets are used.
This page contains information about the mod version of DayZ. Standalone information is available here.