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 scoped Gauss rifle is an advanced sniper rifle that uses a series of eleven electromagnetic coils to energize and magnetize a preloaded standard projectile round to a tremendous speed. In appearance, it is almost identical to the Gauss rifle acquired after finishing the Fallout 3add-onOperation: Anchorage, apart from the addition of an extra pad on the buttstock.
Like most other energy weapons in Fallout: New Vegas, this weapon is hard to maintain; Gauss rifles are rare in the Mojave, therefore making it more difficult to repair. Ammunition is also harder to come by than other weapons; this is coupled with its requirements of five microfusion cells per shot, as opposed to its Fallout 3 counterpart, which required only one.
The Mojave Wasteland version of the Gauss rifle also lacks the knock-down effect that the Fallout 3 version had. It does still apply force to nearby enemies on projectile impact, though that force is largely negated unless the target is dead, in which case it will typically send the target's corpse flying.
In Hardcore mode, if more than 260 microfusion cells, or 52 shots, are carried, the Gauss rifle becomes heavier than the anti-materiel rifle. With the Heavyweight perk, it comes down to 60 cells, equivalent to 12 shots.
YCS/186 - A unique variant that does over 16% more damage and uses four microfusion cells per shot instead of five. It can only be obtained without the Wild Wastelandtrait, otherwise it will be replaced by the alien blaster.
Elijah wields a non-playable version of the Gauss rifle. It only differs from the regular Gauss rifle in damage, which scales to the Courier's level. The damage increases at levels 10, 20, 30, 40, and 50, ranging from 50 to 208 damage per shot.
The following is based on developer test content cut from Fallout: New Vegas and has not been confirmed by canon sources.
The rifle has numerous advantages over its Guns skill equivalent, the anti-materiel rifle. It has a lower Strength requirement of 5 compared to 8, does slightly more damage, has double the critical chance (a maximum of 76% compared to the 38% of the anti-materiel rifle), has more common ammunition, and weighs less. Finally, it has enough range to hit anything the Courier can see, whereas bullets may be unable to hit targets at the edge of their vision depending on their position and direction.
When used in combination with the Meltdown perk, enemies killed with the rifle will frequently be launched incredibly high. This is due to the force that is normally applied to the target upon impact being compounded by the perk's explosive effect.
The AP requirement in V.A.T.S. for this weapon is actually higher, as reloading a weapon costs some AP as well and this weapon has to be reloaded in every shot, so the AP requirement is 10 AP higher in practice (as defined by the "fActionPointsReload" setting in the toolset).
The magnification level for the Gauss rifle's scope is x3.5.
A single shot in Hardcore mode will use 0.5 pounds of ammunition, costing at a combined value of 15 caps per shot.
Because the Gauss rifle uses five microfusion cells per blast (which only accounts for one shot), it's only possible to get one empty microfusion cell from firing the rifle. This is also the same with all energy weapons that use more than one cell per shot.
Its Vault Boy icon, displayed in the Pip-Boy 3000, is different than the one used in Fallout 3. The weapon's shape is also slightly different, having an extra pad on the shoulder stock when compared to the Operation: Anchorage iteration of the weapon.
Despite the fact that the Gauss rifle fires magnetized rounds, no ammunition other than microfusion cells are ever consumed. More rounds never have to be put into the rifle, making its supply of preloaded magnetized rounds a mystery.
When aimed straight down, the blast from the rifle will not knock the Courier down, nor will they take any damage, unlike with the Gauss rifle in Fallout 3. The shield indicating that the weapon's damage is being absorbed by the Courier's DT will appear.
PCPlaystation 3Xbox 360 The Pip-Boy's displayed damage per second (DPS) for the gun doesn't account for the need to reload every shot, unlike other single-shot weapons such as the missile launcher. This is due to the game mechanics not taking into consideration the weapon use of more than one ammunition per shot. [verified]
PCPlaystation 3Xbox 360 The Gauss rifle's shot will rarely completely pass through an opponent when shot outside of V.A.T.S.. [verified]
PCPlaystation 3Xbox 360 The Gauss rifle in Fallout: New Vegas is almost identical to the one found in Fallout 3, and thus suffers from similar bugs, including the one that affects its damage output when fired via V.A.T.S. When used in V.A.T.S., any hit will do exactly 95.244% of the maximum damage, regardless of the enemy damage threshold, critical hits, or sneak attack critical. This means, that with an Energy Weaponsskill of 100, the Gauss rifle shot will do 114.29 points of damage with every V.A.T.S. shot. This is still lower than free aiming, and no bonuses are applied to headshots. The damage bug is related to the Gauss rifle's "explosive" visual effect, which affects its V.A.T.S. damage calculations: the Gauss rifle's projectile is the only projectile in Fallout: New Vegas which is both a hitscan projectile and one which has an explosive effect. Removing the effect from the projectile via user-created mods is currently the only known solution to the issue. [verified]
Playstation 3Xbox 360 When scoped in, the rifle may show a high-contrast color computer interface as shown when activating a terminal, meaning the view will be completely impeded. [verified]
Playstation 3Xbox 360 When standing still and aiming straight down, then firing the weapon, the Courier will sometimes go into third-person, and the weapon will then fly out of their hands. While in third-person, the weapon will now fire directly from where it lies on the ground, or sometimes, float in the air. If entering first-person, the weapon acts like normal. The bug can be fixed by unequipping the weapon completely and re-equipping it again. This is also possible for its unique variant, the YCS/186. Since both weapons have small area-of-blast damage, this will also damage the Courier for about one-tenth of their health. [verified]
↑Emil Pagliarulo in the Bethesda Game Studios forum  - "The gun energizes and magnetizes a standard projectile round; those are already preloaded into the weapon, and are in that giant clip attached to the side of the weapon... We did it this way because we knew we wanted to have an energy weapon equivalent of the sniper rifle"