A firearm flash hider can include a base module having an attachment surface, an exit surface opposite the attachment surface, and a projectile aperture oriented through the base module to allow a projectile to pass therethrough. The flash hider can include a plurality of contoured deflection walls extending longitudinally from the exit surface and further extending radially from a longitudinal boreline axis extending from the attachment surface to the exit surface along the projectile aperture. The contoured deflection walls can block a line of sight to the boreline.
