Tracer

Tracer ammunition was first developed by the Terran Hegemony in 2300. For use in autocannons, it was used to coordinate fire during nighttime operations, with self-illuminating "tracer" rounds interspersed among the normal ammunition. However, the popularity of cheap, mass-produced firepower lead to a decline in tracer ammunition. Modern autocannons, if they bother to arm themselves with tracer rounds, tend to intersperse one tracer round between every fifty normal rounds.

Game Rules
In game terms, Tracer ammo is equivalent to standard ammo in terms of weight and range. It inflicts -1 point of damage per shot (down to a minimum of 1) while at the same time reducing to-hit modifiers for night combat to +1 and eliminating dusk/dawn modifiers.