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 37-12 was a 4-round, pump-action shotgun chambered for 12 gauge ammunition. As the shotgun features dual underbarrel tube magazines, it may be possible switch between the tubes at will, although Ripley nor any others are seen doing so.
The 37-12 is a very effective weapon in close quarters, especially against unarmored humans. Standard Working Joes can be deactivated with a single clean headshot, and while their industrial counterparts may prove to be more of a challenge, three or four direct headshots should terminate them. Notably, a direct shot from a 37-12 is capable of temporarily stunning a Xenomorph, although indirect shots prove ineffective.
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 RXF-M5 EVA Pistol seen briefly in Alien. In fact, the RXF-M5 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.