The Henjin-Garcia Model 37-12 Gauge Pump Action, also known simply as the 37-12, was a 4-round, pump-action shotgun chambered for 12 gauge ammunition.
In 2137, the 37-12 was used by many residents aboard Sevastopol Station, especially when a Xenomorph Drone was birthed aboard the station. Notably, Amanda Ripley, who got hers from a corpse, used a 37-12 aboard the station.
The shotgun will usually kill unarmored survivors instantly, no matter where the shot placement is. Due to their riot armour, Seegson Security operatives are capable of taking more hits, though a single headshot should still kill them. The shotgun is also capable of killing standard Working Joes instantly with one or two headshots, and industrial Joes with three or four. Notably, it is capable of temporarily stunning the Alien, giving the player a very small opportunity to escape.
Behind the scenes
The design of the Model 37-12 Gauge Pump Action is primarily based on the SWATriplex-18, an obscure prototype 12 gauge semi-automatic combat shotgun that was designed in the late 1970s by John W. Winter. The shotgun was never mass-produced because Consortium W, the company which was supposed to manufacture the weapon, pulled out after only a few prototypes were built and Winter was never able to attract anyone else to manufacture his shotgun.
While influences in Alien: Isolation are mainly taken exclusively from Alien rather than its sequels, several elements of the shotgun's design take inspiration from Aliens — for example, the "vents" on the front of the barrel are clearly inspired by the Pulse Rifle's ventilation cuts, while the pump handle is inspired by that on the Pulse Rifle's grenade launcher. Similarly, the weapon's name is perhaps a reference to the Ithaca Model 37, the shotgun memorably carried by Corporal Hicks in Aliens. In the early design stages, the shotgun was to be manufactured by Weyland-Yutani, but this was changed to Henjin-Garcia for the final build.
Additionally, like the flamethrower in the game, the pistol grip of the 37-12 appears to have been slightly based on the grip of the Rexim-Favor-based laser pistol seen briefly in Alien. In fact, the laser pistol was apparently originally going to be usable in the game, being featured in numerous pieces of concept art, but it only appears in a drawing of Marshal Waits in the final version.
The low 4-round capacity of the 37-12 seems strange, especially considering that it features dual underbarrel tube magazines. However, Ripley is never seen performing an action to switch between the tubes during reload animations, so it is possible she simply only ever loads one of them.