The Gauss rifle is a coilgun, a type of projectile accelerator, which uses electromagnetic coils configured as a linear motor to accelerate ferromagnetic or conductive projectiles to extreme velocities. Though these weapons were historically suffering from a number of difficulties, focused on discharging the coils in sequence or providing enough power for the coils, these design issues were overcome by German scientists in the 21st century and entered limited service. This class of weapons is named in honor of the German mathematician Carl Friedrich Gauss, responsible for formulating the math underlying the magnetic acceleration principle of coilguns.
The hardened Gauss rifle is an improved coil gun featured in Fallout Shelter that fires shards of metal at high speeds using magnetic coils that are powered by microfusion cells. Dealing a minimum of 16 damage per attack, it has the highest damage output for a projectile-based rifle in the game.