Liberators

“Completely polymer firearms. No metal, unconventional propellant, advanced polymer armor piercing slugs… Virtually undetectable. They are made by Terran intelligence and fucking hard to get but for you guys I made it happen ‘cause I like you." Sheila Donovan, Chapter 3: Precious Cargo

Most likely based on the World War 2 Gun FP-45_Liberator and it's update, the Liberator .380. Created by the Terran Intelligence Service to hard to detect by the use of Polymers and exotic propellants.