Railers fire extremely quickly compared to ordinary Sniper Rifles. The projectiles they fire bounce off surfaces and pierce enemies. They consume 2 ammo per shot.
Railers have greater base damage than equivalent-level Sniper Rifles, but have a multiplicative penalty to critical hit damage. Functionally, this reduces the effectiveness of critical hit bonuses; the larger the bonus, the less effective Railers will be when compared to regular sniper rifles, making it an especially poor choice for Zer0.
Zer0's B0re skill does not affect this weapon because it already penetrates enemies, overriding the ability to trigger B0re.
Gaige's Close Enough skill can trigger after the weapon has pierced through an enemy. It cannot cause further damage to the initial target, but functions normally when bouncing towards other enemies.
Maliwan - Higher elemental effect chance. Impacts cause a small splash effect.
Dahl - Burst fire while zoomed.
The Railer is a direct reference to railguns, weapons that use immense electric currents and the magnetic fields they generate to accelerate conductive projectiles (or sabots containing non-conductive projectiles) to incredible speeds.