A large framed semi-automatic pistol, the SIG-Sauer 14mm handgun is unique in more than just looks. Unlike the tilting barrel system used by the vast majority of pistols, it relies on a fixed barrel without a slide. A weight underneath the front of the barrel absorbs the recoil, actuating a bolt which extends backwards above the shooter's hand, before being forced back by a recoil spring, feeding another round into the chamber. The 14mm pistol was imported to the U.S. from Europe in limited quantitites, making them a rare, but powerful weapon. As the availability of 14mm Euro ammunition decreased, existing and new units were converted to fire 12.7mm ammunition.
In Fallout, the Sig-Sauer is a powerful, large-caliber handgun equaling the double-barreled shotgun in damage per shot, but with a significantly greater range and magazine capacity. As such, it compares favorably to most other non-energy pistols in the game. It uses the submachine gun sprite, which makes it usable by SMG-oriented NPCs like Ian and Katja.
In Fallout 2, the 14mm pistol is crippled by the absence of hollow point ammunition, as the only round available for the weapon, the 14mm AP (along with most other AP ammunition) was given the unfavorable Damage Modifier of 1/2. This halves the weapon's damage output, seriously affecting its usefulness in the later stages of the game.
The 14mm pistol, despite being called a pistol, uses submachine gun animations. This prevents certain characters like John Cassidy or Vic from using it, but allows others such as Katja and Sulik to do so.
According to the Fallout demo, the SIG-Sauer 14mm pistol's name was originally "S-S Semi Auto Pistol." The name was changed and a short description added.